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Participant

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Which is More Dangerous: AC or DC?

10/30/2006 10:11 PM

Which is dangerous, AC or DC? Why? Why do we prefer AC for our house hold appliances? Why not DC?

Why is the frequency of an AC supply standardized as 50Hz & 60Hz? What is the diference between these two?

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The Feature Creep

Join Date: Feb 2005
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#1

Re: which is dangerous

10/31/2006 8:36 AM

AC is MUCH more dangerous. It has to do with the amps. Voltage can be insanely high, I've seen people get hit with 1,000,000 volts in a presentation, but at 8 amps across the heart your a gonner.

As a mater of fact the only reason we use AC in household electricity is because it travels better over long distances. The electric chair was created as part of the Edison/Westinghouse feud to show just how dangerous AC current was and that it was stupid to have it in a home.

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Anonymous Poster
#2
In reply to #1

Re: which is dangerous

11/01/2006 12:24 AM

Ac dont move better in long distance just because it is AC. but in can be converted to high and low voltage to transmit a low loss.

In fact AC is poor mover on same size of conductor due TO its tendancy to move on surface. thats why we use multystrand cables.

AC is widely accepted because of the fact that equipments and appliances designed for AC are easy to make, inexpansive and more durable. in comparision to DC.

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Anonymous Poster
#29
In reply to #2

Re: which is dangerous

11/02/2006 10:00 AM

N. America freq is 60Hz. Skin effect is minimal to neglible at this freq. Multi-strand used primarily to ease installation (i.e. easier to bend than solid of same AWG).

AC can be transmitted over great distances because of it's frequency, through the use of high voltage and transformers. The choice of freq may have been arbitrary, but is above the level that a human can perceive the oscillation (25 Hz).

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Anonymous Poster
#34
In reply to #29

Re: which is dangerous

11/03/2006 12:15 AM

The Wire is multistranded also to facilitate the messenger wire in the core which give it (aluminum) the ability to span great distances with out stretching or snapping under load (strain).

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Anonymous Poster
#60
In reply to #2

Re: which is dangerous

02/08/2010 7:37 AM

NOT TRUE AT ALL

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Guru

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#3
In reply to #1

Re: which is dangerous

11/01/2006 12:26 AM

The reason AC can be sent over large distances is because it can be passed through a transformer to step up the voltage and reduce the current (and therefore the IR losses) during transmission, then step it back down to usable voltage and greater current near the destination. With AC (single phase), the voltage is zero every 100th of a second (50Hz) or 120th of a second (60Hz), so you have a chance to pull back from a shock. With DC of the same voltage and source current capability, once the contact is made, you have no chance to pull back. (Ever watch the spark you could make with a 300V "B" battery?)

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Anonymous Poster
#15
In reply to #3

Re: which is dangerous

11/01/2006 10:20 AM

Am pleased with your contribution but how are the two types of cuirrent generated?

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Anonymous Poster
#61
In reply to #3

Re: which is dangerous

03/11/2010 4:04 AM

you r wrong

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Participant

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#10
In reply to #1

Re: which is dangerous

11/01/2006 7:39 AM

but at 8 amps across the heart your a gonner.

I thought lethal was measured in mA? 8 amps is overkill from what I understand...

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#21
In reply to #10

Re: which is dangerous

11/01/2006 1:27 PM

Yes, lethal is measured in milliamps. Actually, at high currents, you are more likely to get burned, and often less likely to get killed. There is quite a range of effects due to amperage: some will stop the heart, some will cause it to fibrillate, some are likely to cause enough muscle contraction to throw you away from the source, etc. Ordinary household 110/120 remains the biggest killer in the US.

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#12
In reply to #1

Re: which is dangerous

11/01/2006 9:36 AM

I have always been told that DC is more dangerous. DC does not have the spark arresting property that AC does (reversing direction 60 times a second). DC switches and breakers are more difficult to design.

The selection of 60 Hz and 50 Hz was probably somewhat arbitrary selected. It is just a function of what rpm the generator is spun at and the number of poles. If I remember correctly, AC power for many intracity rail lines was (is) at 16 2/3 Hz.

The electric chair was a marketing ploy by Edison to create the illusion that AC was the "death" current. DC current would also work for an electric chair, it would just be more dangerous for the executioner.

Edison's vision was for there to be numerous distributed DC power stations (as DC does not travel well over distance). With Tesla's inventions, Westinghouse demonstrated that AC power was financially superior and permitted large central generating plants (and annoying high tension power lines everywhere). The 1892 Columbia Exposition in Chicago was electrified by Westinghouse AC power at half the price Edison offered to do it with DC. It was a pivotal point in the ascendency of AC power over DC power.

I did some work in New York City in the 1990's, and some of the older buildings still had DC systems with rectifiers to convert the incoming AC power. A carry-over from when Edison electrified the city with DC power. Rather than rewire the buildings and replace all the lighting and motors in one fell swoop, they maintained the existing systems and rectified the incoming power. The buildings I was in had curious mixes of mostly AC power with some DC power.

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#44
In reply to #1

Re: which is dangerous

11/06/2006 1:27 PM

Kind of off topic, but that electric chair from the Edison/Westinghouse feud was kind of an immense disaster. In fact it is probably in large part because of that incident we DO have AC in our homes.

http://en.wikipedia.org/wiki/War_of_Currents

http://en.wikipedia.org/wiki/William_Kemmler

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Anonymous Poster
#67
In reply to #1

Re: which is dangerous

10/20/2010 1:14 PM

dc is more dangerous because ac is of fluctuating nature .its amplitude varies from maximum to zero and zero to minimum .if someone gets shocked then due to its fluctuating nature,when it reaches at zero value then it releases that person.on the other hand if someone gets shock by the same voltage of dc current then it can be very dangerous for that person because the amplitude of dc is always constant.

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#4

Re: Which is More Dangerous: AC or DC?

11/01/2006 12:56 AM

Experience tells me that DC grabs, AC throws. A friend of mine suffers from the loss of the use of two fingers and two thumbs from a 12VDC lighting circuit (amperage unknown). I suspect that this thread may be hijacked by Luddites who think that DC is safer, because most solar apps go to DC. May the spirit of Nicola Tesla haunt them.

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Commentator

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#53
In reply to #4

Re: Which is More Dangerous: AC or DC?

12/13/2007 9:21 PM

But there is now or soon to be on the market an AC output at higher efficiencies than the normal DC

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#54
In reply to #53

Re: Which is More Dangerous: AC or DC?

12/13/2007 9:22 PM

Sorry. I forgot to add from "SOLAR"

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#5

Re: Which is More Dangerous: AC or DC?

11/01/2006 1:42 AM

I found the following article I think it may be useful; if anyone suspect its contents please comment.

The Advantages of DC Transmission over AC Transmission Systems

Currently, the transmission of electrical power from bulk power generators all the way to household, commercial and industrial consumers is made through high voltage alternating current (AC) transmission and distribution systems, and through a series of voltage transformations to reduce losses and minimize cost. Voltage levels used are of standard values.

AC system is used in the transmission of bulk power, instead of DC (Direct Current), because of its ability to transform voltage to various levels by using a transformer. The voltage transformation follows the faradays Law which states;

The emf induced in a circuit is directly proportional to the time rate of change of magnetic flux through the circuit.

Note that, at higher voltage, the current was reduced thus line losses was also reduced.

Ability to transform voltage and to flow power in two opposite directions (bidirectional) are the only advantages of AC system over DC system.

DC transmission system on the other hand has more advantages over AC transmission system:

1. Reactance.

DC system does not introduce a reactance in the line.

2. Resistance

DC system reduces the amount of resistance in the line.

3. Power

In DC system, the power is just the real component.

4. Frequency

In DC system, the frequency is zero, thus no frequency variation to monitor. Connection will not also require synchronization.

3. Susceptance

DC system does not introduce susceptance in the line thus removing the effect of charging current.

4. Analysis

Analysis of AC system always involved complex numbers, while DC is only a real number, thus simplifying the analysis.

If DC system has the ability to transform voltage into various levels, efficiently, the DC transmission system will the more efficient, stable, easy to monitor, and most importantly, easy to analyze than AC system.

Currently, the transformation of DC voltage into another level involves 3 steps;
1. AC to DC Rectification
2. AC to AC transformation, and
3. DC to AC Conversion

If compared to AC system voltage transformation, steps 1 and 3 are the only added steps. Unfortunately, these steps incur additional heavy losses. However, modern technology converter/inverter has attempted to reduce the amount of this loss. A 1000 MW, 230 KV AC - 450 KV DC/ 450 KV DC - 230 kV AC converter/inverter, for example, has a combine power loss of around 1.6 %.

The use of DC system in the transmission of power will be more economical if the price from its benefits is higher that the cost incurred from the addition of rectifier and converter.

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#14
In reply to #5

Re: Which is More Dangerous: AC or DC?

11/01/2006 9:50 AM

Hazkhod,,,,,,

Where on earth did you find that article??

It is total rubbish.

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#19
In reply to #5

Re: Which is More Dangerous: AC or DC?

11/01/2006 1:20 PM

Wow. On the basis of this article, I'd cross off that source as being reliable.

"Analysis of AC system always involved complex numbers, while DC is only a real number, thus simplifying the analysis." ??? Gadzooks!

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#56
In reply to #5

Re: Which is More Dangerous: AC or DC?

12/08/2008 4:25 AM

Hi I am also thinking something similar line. I am trying use DC instead of AC for my server room feed. I have test that SMPS peacefully work with DC. My problem is whether the same feeder cable holds for DC which is being used currently AC. The cable size is 16sqm.

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#57
In reply to #56

Re: Which is More Dangerous: AC or DC?

12/10/2008 1:40 AM

Hello everybody, nobody answered my question of whether I can use same AC feeder cable of 16sqmm for feeding DC at same voltage?

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#68
In reply to #57

Re: Which is More Dangerous: AC or DC?

02/11/2011 4:50 PM

British Standard 7671 doesn't care either way. The cable size has only to do with the current flowing and the permissible voltage drop, which isn't stated in either post.

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#64
In reply to #5

Re: Which is More Dangerous: AC or DC?

04/28/2010 4:01 PM

THANK YOU SIR

FOR GIVING UR CONTRIBUTION TO ELECTR IC ENGG, UR KNOWLEGDE IS SUPERB

ADITYA MAURYA

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#6

Re: Which is More Dangerous: AC or DC?

11/01/2006 2:09 AM

I'm sorry this has got to be one of the most clueless threads to date. DC does not lower resistance. At power line frequencies the skin effect is very small and reactance is also very small. AC switches off 120 times per second giving you some chance to let go where as DC does not so in that regard AC is safer but the alternate current pulses of AC if they go through your chest probably increase the likelihood of stopping your heart at an otherwise non-lethal level so both will kill you but it just depends. The AC induction motor is at the heart of most modern appliances and it only works on AC. The alternative is shorter life an higher maintenance costs to use DC motors. Edison was deluded into thinking that DC was the way to go mostly because he had a vested interest and so he mounted a scare campaign against AC. For as great of an inventor as he was he was somewhat of a hack and purported to be somewhat of a jerk. DC is infeasible in AC power transmission in so many ways it's not funny. Even your car generates electricity with an alternator (AC) and then converts it to DC because generating DC requires field commutation (brushes and commutator = wear, higher cost, less efficient). It just goes on and on.

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#13
In reply to #6

Re: Which is More Dangerous: AC or DC?

11/01/2006 9:49 AM

Well said rcapper..... there's a lot of nonsense being talked about on here...

I thought this was an engineering forum not a school playground...

John.

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#18
In reply to #6

Re: Which is More Dangerous: AC or DC?

11/01/2006 12:48 PM

Rcapper,

"The alternative is shorter life an higher maintenance costs to use DC motors."

I have found your statement (above) to be very accurate. We run 17 miles of automated conveyors and of course use 3ph 480VAC. Many of the AC motors have been running for 10 yrs. Failure occurs but is relatively rare.

We also have a large fleet of material handling lifts and order pickers which are DC powered. (These are operated 24 - 5)The lift motors vary in size from 1 hp to 25 hp. The failure rate for these DC motors is very high. We replace motors 2 to 3 times per year on many of these lifts.

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#35
In reply to #6

Re: Which is More Dangerous: AC or DC?

11/03/2006 8:01 PM

Alternators in cars use brushes on slip rings so there is no real manufacturing advantage there. The advantage comes in being able to generate current at low engine rpm as well as being easier to regulate and rectify higher engine and therefore higher generator speeds. It's also very hard to store AC in a battery

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#47
In reply to #35

Re: Which is More Dangerous: AC or DC?

11/07/2006 12:58 PM

Reply to 35#

Advantage of alternator is the field rotates while the coils producing the output are fixed (opposite way round from a dynamo) so only the field current, ~ 10% of the output current, goes through the brushes, which can be smaller. Also a commutator is segmented whereas sliprings are continuous strips of smooth metal, so easier to make and less wear on the brushes. Downside of course is the coils produce AC which has to be rectified for the car's system.

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#55
In reply to #35

Re: Which is More Dangerous: AC or DC?

12/05/2008 4:48 AM

ac is more dangerous because 5ov dc is 50v dv but 50v ac is actualy 140v. (peak to peak)

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#7

Re: Which is More Dangerous: AC or DC?

11/01/2006 3:14 AM

Simple answer for part A is that DC is more dangerous because in case of an electric incident you 'clamp on' and freeze to the electricity source. With AC you basically get thrown away for the source. Therefore with AC you get a shock, and survive, and with DC you can be release yourself unless the supply to interupted soe you could be killed!.

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Anonymous Poster
#31
In reply to #7

Re: Which is More Dangerous: AC or DC?

11/02/2006 10:19 AM

This is a common myth. Either DC or AC will "throw you off" or "lock you on". It all depends upon the voltage and the path of current flow through your body. The 120th of a second zero voltage is not enough time for you to relax you grip and pull away. Most DC applications are of low voltage (below 100v) and will have a shorter path to ground through you body at critical current involving muscles local to the point of contact, thus only the contraction or extention muscles are involved. With high AC voltages, the current can travel through the length of you body (from you hands to you legs), where your legs are stronger. Hence, the reason why the military originally required electricians to keep one hand in their back pocket.

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#8

Re: Which is More Dangerous: AC or DC?

11/01/2006 4:10 AM

From a safety point of view it really doesnt matter...just assume that

all electrical power can kill you. A current as low as 100mA can stop

your heart [ can you be sure your hearts in good condition?]

Muscles contract with a positive supply and expand with a negative and

this is the reason why high voltage DC lines tend to be negative wrt. earth

as any contact throws you off.

Note that the only military personnel allowed to work with their hands

in their pockets [ one hand actually] are electrical technicians, as any

inadvertant contact with a supply will travel down one side of the

body to earth and hopefully not across the heart.

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#9
In reply to #8

Re: Which is More Dangerous: AC or DC?

11/01/2006 4:27 AM

Never forget, AC or DC, 'It's Volts that jolts, but Mills that kill'

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#11

Re: Which is More Dangerous: AC or DC?

11/01/2006 8:28 AM

good question there.. but i think it always depends on the volume. doesnt matter if it is ac or dc its a design and nothing to do with being dangerous or not

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#16

Re: Which is More Dangerous: AC or DC?

11/01/2006 10:48 AM

There would appear to be some miss-conceptions here from people who have obviously never been inadvertently attached to either DC or AC in the killing ranges of voltage. I have!!

I worked on both AC and DC NATO alliance ships.

I served over 10 years in the Royal Navy (63-73).

You may like to ask yourself why all DC ships (except Carriers with Ring Mains systems),(built upto about 1950-54 or so, had open DC switchgear, but excepting one ship which had for a short time open AC switchgear which promptly killed several people....it was then all closed up for AC!!! Only the one ship was ever built with open AC switchgear.

AC will hold you on as the muscles sort of lock due to the frequency, whereas DC throws you off,or you really inadvertently pul your hand awayas the muscle shortens suddenly.

As far as I am aware, nobody was ever killed with 220volts DC, (I am sure someone was, I just never heard about it!) I know a few who got burned while holding metal objects which got hot due to shorting of DC!! I have seen that at close hand in Singapore, on an old 220Volt DC Ring Main aircraft carrier!!

It is sad to say that relatively quite a lot of people got killed with AC voltage on NATO ships though....

DC has good and bad properties with regard to control, just as AC has.Mostly opposite to each other....Speed control with DC is easy for example, but you need so called 'Magenetic Blowout' coils to 'puff' out the arc when breaking/opening heavy currents. AC needs no Blowout coils, but speed control is very difficult for example!!

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#23
In reply to #16

Re: Which is More Dangerous: AC or DC?

11/01/2006 4:27 PM

i worked on electric locomotives for 20 years they use 1500v dc

once there was someone who touched live 1500v dc he was thrown off the roof of the locomotive by the dc current

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#17

Re: Which is More Dangerous: AC or DC?

11/01/2006 11:01 AM

Which is dangerous, AC or DC?
- Yes.

Why?
- because either will cause electric current to flow, either pulsed or not, through the bag of electrolytes known as your body, and either interupt the signals to your life processes or simply short them out and burn up the signal paths like a melted fuse element in a liquid media. DC+ causes muscles to contract, DC- (with respect to zero-plane/ground) causes muscles to extend, and if of sufficient current, the nerves will be damaged as well as the tissue burned as the water is boiled out of it and the flesh is cooked. AC+/- will create it's own path from any two connection points, and if the heart or it's nerve bundle are in the way, you risk that quick, regular, large 'signal' at 50 or 60 Hz causing the heart to go into arrest, since it just wasn't designed for that...and again, sufficient current above signal level causes damage that may make it impossible, especially in those few crucial seconds afterward, for the body to make the normal signals take back over.

Why do we prefer AC for our household appliances?

- Because it was by far more economical to build the original transmission systems around generating AC, stepping the voltage up high to use smaller diameter multi-strand wires, then step it back down at distributed end locations, as well as the ability to take advantage of remote power plants burning that dirty coal stuff or from a remote dam, like Niagara Falls.
Also, it's cheaper to do useful work (except possibly resistance heat, but who wants to do much of that) with AC induction motors, both initial cost and lack of required maintenance. Most housewives aren't electrical repair technicians. And just try to make a cheap DC microwave oven, DC compact fluorescent ballasts, DC ground-fault circuit interuption to prevent fires or danger from a line-to-case ground fault in a DC hairdryer dropped into the bathtub...maybe once we all go to LED lighting?

Why not DC?
- Because we don't simply "light" the house with Edison bulbs and heat water and air, we run motors and electronics, which are now all based on seeing AC and would be world-economy busting to change out now, even if other challenges were solved or some perceived issues seen as advantageous.
As distributed solar/wind/other user-generation systems gain economical advantages, we will likely see more homes and businesses with hybrid systems, using the DC directly from a battery bank only where economical to do so, and inverting the excess to run their utility meters backwards when possible.

Why is the frequency of an AC supply standardized as 50Hz & 60Hz?
- 50Hz was seen as 100 switches per second, which went along with the prevailing metric (International Standard) way of engineering everything at the time electricity generation was developed in Europe, and it spread from there.

- 60Hz was Tesla's consideration that this was a time-based design, and there are, for instance, 60 seconds in a minute, 60 minutes in an hour, and it seemed to make sense to time it out for 60 peaks per second.
i.e. rather arbitrary, and the rest didn't want to simply 'copy' an arbitrary design, but think through (and argue loudly about) and come up with a 'more logical'...but still arbitrary conclusion. It could have been 100Hz, as some argued at the time...

What is the difference between these two?
- Well, one system is timed to provide 50 cycles per second, and the other stayed with the original 60 cycles per second, for one thing... ;)

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#69
In reply to #17

Re: Which is More Dangerous: AC or DC?

03/23/2012 12:08 PM

Best advice to give: Sh*t yourself for both when working live.

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#20

Re: Which is More Dangerous: AC or DC?

11/01/2006 1:25 PM

Ok my 2 cents worth.....AC costs less when considering manufacturing costs for low cost products. If you use DC then you must supply a battery pack with replaceable batteries (passes on cost to consumer for long term usage) or supply a battery charger with product or you may rectify the AC line voltage to produce DCV then use it. It is simpler and more cost effective to use AC line voltage and not have to add a rectifier circuit and additional circuitry to stabilize and filter the DCV produced...It is economics....

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#22
In reply to #20

Re: Which is More Dangerous: AC or DC?

11/01/2006 2:20 PM

Solar panels will soon have a microchip to deliver 110 volts. That should simplify a lot of things. And it will deliver more energy than the current panels as well.

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#24
In reply to #22

Re: Which is More Dangerous: AC or DC?

11/01/2006 8:51 PM

Huh?

Solar cell voltage is based on the size and composition of the cell. You get more voltage by having more cells. 5V, 60V, 110V, 1000V, it's all irrelevant with regards to any "microchip", it's just how many cells you have.

There are already many "microchips" available to allow inverters to recreate AC power from any DC source such as a solar cell. Getting more energy out of a solar cell has nothing to do with a "microchip" either. There are people working on increasing the conversion efficiency, but the result will be measured in milliamps, and again, has nothing to do with voltage.

This entire thread is amusing if for no other reason than to see the misconceptions that are out there. As several others have said, AC and DC are both dangerous. I work with inverters every day. They convert AC to DC, then back to AC. Several co-workers have indeed been seriously injured or even killed by coming into contact with the DC bus. I have come into contact with 480V AC on numerous occasions, I have never been hurt as of yet. My worst electrical burn came from my car battery, 12VDC.

The concept of which one is "more" dangerous is a moot point, one missed entirely by any person who comes into contact with either one. It's kind of like arguing whether it's better to be vaporized by an chemical bomb or a hydrogen bomb. AC and DC both have their legitimate uses, the decision to use one or the other should be made based on the applicability of its use, not some useless concept of relative safety.

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#25
In reply to #24

Re: Which is More Dangerous: AC or DC?

11/01/2006 8:57 PM

How little do you know ! You repeat the current state of affairs, not what is coming down the track. And it is twice as efficient and a lot cheaper than a conventional panel.

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#28
In reply to #25

Re: Which is More Dangerous: AC or DC?

11/02/2006 6:21 AM

Raknruin, what he says makes perfect sense, adding a 'microchip' is not going to give you higher efficiencies or a higher voltage...

Only the chemistry of the solar cell (or combining many together) will give you that.

Your statement that new solar cells will give you 110 Volts is incorrect, where did you read that from?

John.

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#33
In reply to #28

Re: Which is More Dangerous: AC or DC?

11/03/2006 12:14 AM

I cannot give much info but this is a developed product, new product, which collects all the stray energy hitting the panel. That is why it collects twice as much energy. And converts energy via the chip to 110v.

In addition, it can be adapted to existing panels as well.

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#36
In reply to #33

Re: Which is More Dangerous: AC or DC?

11/04/2006 4:45 AM

I dare say thou doth slosh when thou walks!

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#40
In reply to #36

Re: Which is More Dangerous: AC or DC?

11/04/2006 12:02 PM

All I can say is "Watch this space". This is a developed product soon to hit the market for new panels and also for retro fits. It delivers roughly twice as much as a conventional solar panel. Expected cost per kw hr of around 5 cents US soon.

I can say no more.

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#26

Re: Which is More Dangerous: AC or DC?

11/01/2006 11:25 PM

Dear friend 1)AC is a repulsive shock(because of its sinusoidal nature) while DC is an attracting shock.DC is more dangerous than AC. 2)We prefer AC over DC because of reasons furnished earlier by many friends in the forum. 3)The 50/60 Hz depoends on the speed with which the generator rotates(in RPM).If it rotates with 3000rpm the freq is 50Hz and if it rotates with 3600 RPM the freq is 60Hz(no. of poles being 2).The speed of rotation has a deciding constraint of- inertia of the rotating equipment.Different countries have standardised on different frequencies. Hope i have clarified yr doubt to some extent. regards Ravipra

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#39
In reply to #26

Re: Which is More Dangerous: AC or DC?

11/04/2006 11:48 AM

You wrote: "1)AC is a repulsive shock(because of its sinusoidal nature) while DC is an attracting shock.DC is more dangerous than AC."

Surely you don't actually believe this.

-E

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#27

Re: Which is More Dangerous: AC or DC?

11/02/2006 4:33 AM

Both are dangerous.But it seems that more people believe that AC is more dangerous.

In China,our house hold appliances is usually 220VAC,50HZ

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#30

Re: Which is More Dangerous: AC or DC?

11/02/2006 10:15 AM

Quite correct, AC is more dangerous as anyone will know who has had intimate contact with both will say.....

Of course both can kill and I liked the synonym with regards to being blown up with an atom bomb or a normal bomb.....also correct! Neither are good for your health.

Most of the people who believe that DC is more dangerous are speaking of very high DC voltages, which are of course more dangerous than significantly lower AC voltages....! Makes sense I feel.

I have had many, many contacts with 220V DC, I just swore and carried on working! We had to faultfind earths on live switchgear.

With similar AC shocks, it is like getting your internal CPU reset, your brain just seems to stop for many, many seconds.........! Difficult to judge how long......

Someone once said to me that after an AC shock, he felt as though a giant had clapped his hands and he was sitting on one of the huge palms when they were smacked together....I agree with that........!

Anyone who has NOT had such intimate personal experiences is hardly qualified to comment I feel, sorry.

Let us all agree together that contact with any type of voltage over 65 volts CAN lead to death......also that some people get hit by lighning and live to talk about it!

Contact with any voltage should not be taken lightly, as someone else points out, a car battery (with the aid of a metal watch strap for example) can give life threatening burns. A friend of mine got "welded" to the battery + and the car body some years ago...... the watch strap was white hot!

Always remove all jewelry before working on ANY voltage!

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#32

Re: Which is More Dangerous: AC or DC?

11/02/2006 11:10 AM

dear friends,

Electroman has said it right. I myself was completely lost when l have read some of the comments and articles, may be, we only need to educate people about the danger posed by both power rather than commenting on which is more dangerous. "both are in every degree if the user is ignorant of both"

andynh2

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#37
In reply to #32

Re: Which is More Dangerous: AC or DC?

11/04/2006 9:28 AM

I appreciate your point, and would like to thank you for this. Many comments are informative, and many are just rubbish. What I think both are dangerous if handled wrongly.

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#38
In reply to #37

Re: Which is More Dangerous: AC or DC?

11/04/2006 11:37 AM

Yes, an excellent summary.

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#41

Re: Which is More Dangerous: AC or DC?

11/06/2006 11:36 AM

Comments on various:
All are dangerous, but...
50Hz, 60Hz and DC each have somewhat different physiological effects. On a like-for-like current and Voltage basis, you are more likely to be able to "let go" if the supply is at 50-Hz than if it is DC or 60Hz. I'm told that the differences between 60 Hz and DC are more dependent on the location and magnitude of the currents involved. Incidentally, some nominally high-Voltage battery-supplied DC systems can be relatively safe because the whole system can be floating - so you can touch any one point on the system and only experience a "jolt" while you discharge the potential at that point to ground. These were used in many open-bus systems, particularly in standards-laboratories. I have no knowledge of submarines, but it could be that the DC systems were configured in an equivalent manner.

One other point:
It was stated that the comment in the article about "complex numbers" for analysis of AC was "rubbish". AC transmission over long distances behaves as a wave in a transmission line - which is simplest to analyse using complex algebra [e.g. exp(jwt-x/c). What the article did not mention was that we have equivalent issues when analysing current transients on so-called DC transmission systems, such as were (and may still be) used in northern Asia to overcome synchronisation problems over long distances.

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#42
In reply to #41

Re: Which is More Dangerous: AC or DC?

11/06/2006 12:33 PM

"All are dangerous, but...
50Hz, 60Hz and DC each have somewhat different physiological effects."

What about 400Hz systems?

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#48
In reply to #42

Re: Which is More Dangerous: AC or DC?

05/03/2007 9:27 PM

I too am quite interested in the expected physiological differences between DC, 50Hz, 60Hz and, in particular, 400Hz. Since 400Hz is used on Aircraft, I would think there should be a wealth of information but, I haven't discovered it as yet. Some people will say that the "skin effect" plays a role but, I believe that the skin effect is only a factor at much higher frequencies. However, I am thinking that the impedance of the human body would be a major factor in determining weather or not the currrent through the heart would be enhanced, thus making it more dangerous than 60Hz for a given voltage. Hopefully there will be some additonal thoughts (facts) forthcoming in this regard.

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#49
In reply to #48

Re: Which is More Dangerous: AC or DC?

05/05/2007 3:41 PM

This is, I tend to think, more in the realm of physiology than electricity, because the short and long term influences, of electrical currents, may have many intricate aspects to living tissue in general, and given systems in the living body.

40 volt at 400 Hz for instance, (known telephone standard, cant tell the current), and should you get electrocuted, it is quite nasty, but with no lasting or long-term residual effects, and opposed to, say 240 volts at 50 Hz at the wall-outlet, which is both short and long term nasty business.

...I would think there should be a wealth of information but, I haven't discovered it as yet...

It is an interesting subject nevertheless, and I'll try to look it up, in terms of physiology. You may wish me good luck, as I too, cannot expect much in advance.

Maybe it's there, waiting, in the military-interrogation medical files... Who knows?

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#50
In reply to #49

Re: Which is More Dangerous: AC or DC?

05/06/2007 2:56 PM

Thanks. If you find something, I'm all ears. Below is a current vs physiological effects chart which I believe will be useful for everyone on this thread. (There are several charts similar to this one and as I retrieve more reliable information, I update the information that I have.

Current (ma) Bodily Effect (Based on Canada Safety Council Data-Sheet I-1)

0 to 1 Perception Threshold, Faint Tingling

1 to 2 Muscle Contractions can begin, may be painful

5 Slight Shock, May cause strong involuntary reactions

(Trip rating for Class "A" GFCI's)

6 Can be fatal for children if certain conditions exist

(ie: wet body contact)

9 Let-go threshold for women

16 Let-go threshold for men. Above this figure, depending

on the current's path, chest muscles may contract and

breathing difficulties may develop

50 Ventricular fribrillation can occur under certain circumstances.

Persons with heart Ailments may be more susceptible even at much

lower currents

200 Severe muscle contractions, including paralysis, and collapse may

occur. Unconciousness may develop, the heart can stop and death

ensues

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#43
In reply to #41

Re: Which is More Dangerous: AC or DC?

11/06/2006 1:25 PM

Actually I think my reference to complex numbers said "Gadzooks", not "rubbish". My point was that to suggest that one system is somehow better than another because it is easier to do (and conceptualize) the math is pretty lame. It's a little like saying that Newtonian physics is better than general relatively because the math is easier to grasp.

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#45

Re: Which is More Dangerous: AC or DC?

11/07/2006 5:18 AM

AC is more dangerous for the same voltage. 200V in AC indicates its RMS( Root Mean Sqare Voltage). Its peak voltage is 1.414 times the RMS ie. 282.4V. Hence more dangerous. AC voltage can easily be transmitted over long distances. The voltage is increased at the transmission point and reduced at the distribution point, thereby reducing the transmission losses. Transmission losses are less at high voltage. It is necessary to have standard frequency for synchronization at the grid.

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#46

Re: Which is More Dangerous: AC or DC?

11/07/2006 10:34 AM

Just a historical note. Mexico City 50 odd years ago had two power companies, one working with 50 and the other with 60 hz. So much for the benefits of competition.

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#51

Re: Which is More Dangerous: AC or DC?

11/03/2007 3:04 AM
  • DC is more dangerous than AC because I have seen the person who touched 110VAC have survived but in case if you touch 110VDC than you wouldn't be surviving.
  • Actually we should prefer DC but DC transmission is too costly to transmit for a small distance.It has only advantage when it is transmitted for a distance more than BED (Break even distance i.e 600 KM).
  • When do you get a shock in AC there is a little bit chances of getting survive but in DC you can't survive.
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#52
In reply to #51

Re: Which is More Dangerous: AC or DC?

12/13/2007 3:21 PM

Touch your tongue to a 9V battery. Feel the tingle? Now remove it. Congradulations, you have just survived a DC shock.

People here are starting to get closer to the facts. Voltage alone does not kill you, current alone does not kill you. It is power that kills you. AC and DC are both very dangerous, and both depend on peak voltage and the ability to deliver current.

Other factors to consider, DC tends to prevent an individual from letting go at a much lower threshold than AC. DC is more likely to stop your heart outright because of the constant stream of electricty (holds the muscle in one position) AC is more likely to cause heart fluttering due to the changes in voltage, which can be equally as dangerous.

Some examples of dangerous and not dangerous electricity:

-Static charges (like from your wool sweater) are DC and can carry several million volts, but there is very few electrons carrying this amount of charge and so the current is virtually nil.

-Batteries are DC and can some can deliver quite a bit of current when demanded, but the majority of them are low voltage (say 10V or lower) which prevents significant amounts of power from being delivered to your body (your body has a fairly high resistance which leads to a low current draw V/R)

-Trolley wires are DC, have 600V and the capacity for over 100A, and will kill you very quickly.

-There are very few examples of low voltage AC, but if they have the same power supply as a DC system, they are equally likely to kill you.

-High voltage AC wires, with the large current backing they have, will kill you easily.

Remember, the standard measure for power is joules/second (Watts). This is the same measurement to determine if something will burn you, and whether the speeding car's momentum will kill you instantly. If a system cannot deliver significant amounts of energy (Voltage), it is less dangerous (a lukewarm stove or low voltage system). If a system cannot deliver energy quickly (Current), it is less dangerous (hot rocks dont burn as quickly because they transmit heat slowly, just as low amperage systems transmit energy slowly).

If a system has high voltage (energy potential) and high current capacity (delivery speed) stay well clear! Hope this helps. Feedback is welcome.

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#58
In reply to #52

Re: Which is More Dangerous: AC or DC?

07/09/2009 8:42 AM

both r dangerous depending on v or I

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#59
In reply to #52

Re: Which is More Dangerous: AC or DC?

07/20/2009 5:12 PM

well,it's good but not the exact answer.

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#63
In reply to #52

Re: Which is More Dangerous: AC or DC?

03/27/2010 8:48 PM

Wow. Awesome post. Sums it all up pretty well.

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#62

Re: Which is More Dangerous: AC or DC?

03/12/2010 4:55 AM

Which is More Dangerous: AC or DC?

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#65
In reply to #62

Re: Which is More Dangerous: AC or DC?

10/05/2010 3:01 AM

Which is More Dangerous: AC or DC? Question is wrong. You should ask at same voltage which is dangerous? consider at 110 volt which is dangerous?? so here for dc voltage you will get shock by 110 volt. but in case of ac the peak voltage = root 2* 110=155.56 volt so u will get shock with 155.56 volt... thats why ac is more dangerous at same voltage...

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#66
In reply to #65

Re: Which is More Dangerous: AC or DC?

10/05/2010 12:56 PM

Final word:

It's a know fact that electrocution from DC makes you 38% more dead than electrocution from AC.

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