3 Phase Electric Motors

Mark,

Yes, there are many companies that manufacture/sell single to three phase inverters as well as companies that manufacture/sell single phase motors..

Are the two 25 HP motors the only 3 phase loads you have connected to your service?

If so, then yes, an inverter might be the way to go if this will allow you to eliminate the three phase service ($325.00+ demand charge).

A place to start is use Google and search the following:

"single phase to three phase inverter"

and

"25HP single phase motor"

These should get you results of companies that you can contact and can assist you in making your decision.

If the two - 25HP motors are not the only three phase loads and you must keep the three phase service ($325.00+ demand charge), in my opinion, it would not be worth the time, money, or effort to install inverters on these motors - no savings.

Good Luck

Three phase is more efficient than single phase. Please find yourself a reliable licenced electrician to diagnose your big bill.

Is the $325 the kwh part of your bill, and if so then what is the added demand charge?

Or, is the $325 the added demand charge, and if so then what is the main kwh charge?

Once the motors have been started, do they run more or less continuously, or do they stop and restart a lot?

50hp ≈ 37kw. If 8 hr/day x 30 days/month, this is 8880 kwh/month. $325/8880 ≈ $0.0366/kwh.

I agree - there is no way of knowing what can be done without the "usage" figure.

If there is a huge disparity between 'usage' and 'on demand numbers, then something might be done to limit the peaks causing the high momentary meter reading.

But if the usage is high, or in proportion, then no system is going to be better than 3p.

The OP needs to provide both numbers.

the 2 motors drive pumps that apply the high pressure water. the start and stop

Good luck starting those motors on single phase. For single phase power your amp draw will be about three times what it is now so you will need a dedicated high capacity single phase service installed plus loads of additional stuff to convert over.

Trust me you wont gain enough in your life time to offset the conversion.

However if you are curious as to how a three phase motor can be ran on single phase efficient I have a full write up on how to do it here. http://www.electro-tech-online.com/re-projects/100563-3-phase-converter-schematic-miller-system.html

Changing to single phase motors will not reduce your demand. See if there is a way to prevent both motors running at the same time.

If you are trying to reduce your electric bill by switching from three-phase to single-phase motors - you are DREAMING MAN!

Three-phase motors are much more efficient than the single=phase ones . . . so your bill is going UP!

Quite correct, . . . try to avoid the extra demand charge by not operating both motors at the same time . . can this be arranged??

Oleh

Very correct. You will have 3 additional expenses that will make you dream of your 3 phase motors. 1. A single to 3 phase converter with starter will cost you big money for motors of that size 2. The sheer gauge of wire needed to run those motors on single phase must come directly from the pole. Maybe even an additional transformer, this will cost tens of thousands of dollars my friend. 3. The bill Kwh wise will be insane! 3 phase power is the most efficient (and cost effective) power available. The draw on that single phase feed will be astronomical. Trust me you are going backwards if you get single phase routed there. Get a qualified electrician and have him diagnose your bill.

If the "demand" surcharge is caused by the peak current at starting, consider adding a soft start to your starting contactor. This will cost a few thousand dollars but will reduce the starting current drastically.

Forget about single phase supply for such a large motor. The drive itself will be very expensive, the harmonics will be unbearable and you might never find a such a large drive running on single phase.

Sell the existing 3phase motors and purchase new single phase motors. THis may account to be profitable in the long run.

Inverters is OK. Try to think abt their maintenance,ny repairs etc.

I'm also assuming you're trying to cut your overhead by getting rid of 3 phase
and making your own car wash soap
I'm assuming your operation is a frequent start and stop application being coin operated

As others stated single phase on large loads is bad news and if you change to single phase with a monster load like that I'm sure you will find another demand type meter on your single phase with higher bills than before while you brown out your neighborhood and then when you decide to go back they may charge you another $1200 bucks to hook 3ph back up

If you are a constant run operation maybe a natural gas driven pump might be an answer

Installing capacitors on your 3 phase motor operation would be the first thing I would learn about and talk to with an electrician or an electrical wholesaler or google 3ph power factor correction capacitor mfgs

I'm sure there are pro and cons but I was highly impressed when I used them
I could give you a long list of the pros as a user not as a salesman
and the power companies use them to correct large inductance loads

With $3 dollar per gallon gasoline in the US I hope we will have enough money left to use your car wash

I think your best bet would be to go with a high effiency motor i.e Baldor "Super-E" Check out this link for the calculations of savings: http://www.baldor.com/support/BE$T_features.ppt Fill out the numbers, as best as you can with what is known, and it'll give you an idea of the payback period. These motors have a higher initial cost but the bigger the motor and the more usage it has, will give a faster payback in energy savings. If your demand charge is a "peek useage" charge, It's really hard to save money no matter what you do unless you can lower the initial surge from the motor i.e. soft start, VFD and others? The electric companies make it that way on purpose!

Mark, If the 25 HP motors are driving your blowers, I'm assuming 3600 RPM, there are a couple of alternatives to reduce your peak demand. Assuming that you're already step starting the blowers, (first one and then the other), one solution readily available in the car wash industry is to start them under "no load". There are mfrs that have a louvered system that will block the intake just long enough to allow them to start under "no load" which greatly reduces the start-up current. Inverters (VFDs) are a second alternative, although for 25 HP motors, inverters will be expensive. A third strategy that you should be employing if you operate a conveyor wash is to do a "look ahead" in your conveyor controls so that if the next car coming through will get a dry, the motors do not shut down between cars. In this situation, it's far less expensive to keep the motors running than to restart them 30 seconds later. The louver system can also be employed in this scenario to reduce your idle running consumption. If the motors are driving your high pressure water pumps, then VFDs will be about the only option. Could you supply the following information: (1) What are the motors driving? (2) is this a conveyor wash or an in-bay automatic? In either case, the three phase motors will be more efficient than single phase. From the business perspective, how many cars are you washing during your billing cycle... what is your electric cost per car? What is the average revenue per car vs your electric cost per car? I work in the car wash equipment industry and while I do not sell the items mentioned above, I'd be happy to point you in the right direction if you want to PM me.

Thanks for the reply.

The 25 hp motors drive a cat pump on one automatic and a general pump on my second auto. my dryer motors are 3 phase also. I have to look what the hp is on them.

Your blowers are likely 10HP. Macneil Wash Systems ( macneilwash.com ) in Canada make the powerlock air valve that may me retrofitable to your blowers. They likely have a 4 to 5 second ramp up time with a huge start-up load, and I'm guessing 2 or 3 blowers per automatic?

I'd go to their web site and find out who your local distributor is. It doesn't hurt to call and ask if you can use the powerlock valves on your blowers and what the cost is.

Your HP pumps on the other hand, are likely up to speed at full load within a second or so.

Okay Mark,

After looking at the picture of your wash on google street view, it appears your load is high pressure pumps on two in-bay automatics. VFDs might be cost prohibitive and you may not be able to afford the ramp-up time.

Your best bet is to calculate your cost per car and price your wash packages accordingly. Look on the bright side... The more you pay, the more you made!

Best of luck,

B

thanks fo the info

LOTS of misinformation here.

THERE IS VERY LITTLE DIFFERENCE IN THE EFFICIENCY OF A 3 PHASE MOTOR VS A 1 PHASE MOTOR. Don't believe me? Look it up on any motor mfr's website. That said, there are very few 25HP 1 phase motors available, if any. At 230V, that means over 115A FLC, and that is way too much wire for most people to want to deal with on a motor that size.

Starting current makes almost NO DIFFERENCE in peak demand charges. Demand Meters use a sliding demand window for calculating peak demands. The shortest window length I know of in North America is 15 minutes, some are 20 and 30 minutes. Any short term current spike of less than the demand window is virtually ignored by the meter. Think of your electric stove element moving a needle on a temperature gauge held above it. If you turn the stove on High for 2 seconds and then back down to Low, is the temperature gauge going to see any movement other than what the Low setting represents? Try it!

When you get 3 phase service in North America, you also automatically get a demand meter. Only residential and some very small light commercial single phase services (like small stores without refrigeration or rest homes) get away with not having a demand meter. But if you try to convince your utility you are all of a sudden a "light commercial" user and go back to a single phase service, your utility will NOT remove the demand meter now, they already know! It's too late for that.

The ONLY ways to reduce your demand charges are;

1. Reduce your overall energy use. Demand charges are a multiplier on top of the kWh you use. Reduce the kWh and you reduce the demand charges too. It's a win-win. Look at EVERY part of your operation and consider how you can reduce operating energy. Take nothing for granted, but don't buy "magic boxes" unless you can PROVE they will have an ROI of 2 years or less. Avoid anyone who uses the term "space age" or "Newly Discovered" in their advertising for said devices by the way, they are ALL ripoffs.
2. Shed loads when the demand starts to peak. That is VERY difficult for car washes because of the nature of your business model, but it can be done. Some of the above suggestions specific to car washes are helpful. VFDs are a very common way to reduce energy consumption on pumps and fans, but ONLY if you run a large percentage of time at reduced flow. One strategy I have seen is a demand monitoring system that will slow down the pumps to avoid exceeding a peak level, but it means less pressure in the wash at that time. Hopefully your customers don't notice.

By the way, avoiding the Start / Stop of blowers between cars does save wear and tear on the motors and equipment, but it doesn't really do much for energy savings or peak demand charges. The only time I have seen it make a difference is when you are in a cold area and need electric heater elements in the dryers. When the heaters are used, you can't totally shut down the blowers or the elements get damaged. But rather than leaving them on full speed between cars, you reduce the bower speed to a minimum level to protect the heating elements, then speed them up again as the next car approaches. But if you don't have heating elements, it's pointless.

I am not having eno time to read through your posting, however, posting the following in hope that it would be enough help :(

Cut and paste (but it still required time for reading through a book :

Running 3-phase motors on 1-phase

Three-phase motors will run on single phase as readily as single phase motors. The only problem

for either motor is starting. Sometimes 3-phase motors are purchased for use on single phase if

three-phase power is anticipated. The power rating needs to be 50% larger than for a comparable

single phase motor to make up for one unused winding. Single phase is applied to a pair of windings

simultanous with a start capacitor in series with the third winding. The start switch is opened in

Figure 13.63 upon motor start. Sometimes a smaller capacitor than the start capacitor is retained

while running.

13.7. TESLA POLYPHASE INDUCTION MOTORS 447

f1 R

S = start, R= run

M1

f1'R

S

optional run capacitor

start capacitor

return

fsynthetic

fsynthetic

f1

f1'

f1

f2

f3

synthetic 3-f standard 3-f

Figure 13.63: Starting a three-phase motor on single phase.

The circuit for running a three-phase motor on single phase is known as \add a phase" or various

other brand names. \Add a phase" supplies a phase approximately midway 6 90o between the 6 180o

single phase power source terminals.