Can I Run an Alternator with Electrical Motor?

i am perplexed. Why would you need an alternator if you already have an electric supply to run the motor ? You must be aware that the energy output by the alternator will be less than the energy consumed by the motor.

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Thanks for the reply, so why alternator is run by diesel engine, can't a electricity motor produce 1500rmp to run alternator, electricity produce by alternator can we use to other appliance, i have doubt since childhood so i m asking these question,

OK, many answers ... you need to do some learning to separate the good from the not-so-good.

Go to this wiki page to learn about M-G sets, and why/where they are used.

When i was a child, i also wondered why can't we couple a motor and generator together, the alternator supplies the motor, the motor drives the alternator, and any extra power can be used to light up the house. My father, with infinite patience, explained perpetual motion machines, their impossibility etc. Hence my Avatar as a tribute.

This I have shown a few weeks back to my child (std 6) and you may try it out too.

mechanically couple the motor of a toy car with another. Connect 6V battery on one of the motors and a torch bulb on the other.

Check the glow of the bulb.

Now connect the bulb on the same battery (without connecting to the motor) and check.

The answer will be evident.

Of course after that I had to explain the losses in simple term for him to understand. But that is that.

Mechanical Power (Motor) = η₁. Electrical power.

Electrical Power(Alternator) = η₂. Mechanical power at its inlet

So

Electrical Power(Alternator outlet) = η₁η₂. Electrical Power(Motor Inlet)

In case of DG Set (or other generation equipments) - the power inlet is not electrical- it is chemical(Fuel fired), Potential(Hydro), Nuclear,... converted to Kinetic Energy and that KE is converted to Electrical Energy.

So even at the loss of efficiency, the gain is high (since the only reason of generating Electrical Power is due to its efficient transmissibility). Finally it is overall system efficiency we are interested about from the source to the load.

Yes you can but your alternators output will be lesser than energy consumed by your motor

however if you are looking for some other voltages/frequency/number phases than available, to run your said motor you can do that

Yes, it can be run. But you need a very big motor to run the generator and a very good speed controller to control the speed of your motor and of course, you will loosing power and wasted energy and electricity for nothing. At the end you may have to pay more than to run the generator with a diesel engine.

It is very possible to run an alternator with a motor but there will be a lot of power wasted due to losses associated with both the alternator and the motor. Moreover, why not use the power availabe directly rather than feed it to a motor.

Thanks for reply, can you tell me what capacity of motor i need to run 200kva alternator.

Something over 220kW?

Roughly, 200 HP motor.

Dear Mr.bsnegi91,

Even after giong through all the comments from eminent contributors like Mr.Sridhar, Mr.Slack, you want to know the answer to your query.

There will be some loss when you transform energy from one form to another. In your

case Electrical to Mechanical And then to Electrical. There will be losses and it may

thearitically ok, but not economical. This generator may supply output limited to

Motor Kw input x efficiency of motor x effiency of the alternator. Even with 0.95 %

efficiency at each stage we get only 0.9025.

When I was a kid I wondered whether I can run an an alternator attached to fan shaft and feed the output to the fan & switch off the input power.

My father who was an mechanical and electrical engr explained to me the above point (as explained by Mr.Sridhar).

Manroop.Chennai.

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You mean the Nigeria thing is a scam??? OH NOOOOOO!!!

It sounds like you have a diesel powered generator and you want to convert it over to run with electric motor. I'm really confused........any chance you could install a fuse panel and run your appliances from the same electrical source that you want to use to run your big electric motor.

Dont you know law of conservation of energy. There is always some losses you give input power to a system you get same output power only if you add losses. Hit

Yes, depends on your health and the weight of the motor, you can run. Ofcourse diesel engine will be more heavier than electrical motor. So better you run with electrical motor. But far the distance you have to run?

Yes you can run a Alternator with a electric motor.

To figure the horse power it is 746 watts of power for 1 HP. that means you have to have 1.34 hp for each kw or kva.

The stand rule is to us 1.5 hp per KW or KVA for effencey loses.

Note that most electric motor run at lower or higher rpm's that will change frequncy on you alternator out put.

I have build the systems for the computer industry for some time.

So you will have to factor in the loses in the speed change.

Yes, this arrangement works very well. You have to spin the alternator up by hand to get the system going, but after that, the alternator will supply the electricity to run the motor.

If you put a single diode in the output of the alternator, "back flow" is prevented, so that the motor does not have to work as hard to drive the alternator. With this arrangement, (called a "half wave rectifier", because the motor only works half as hard) the output of the alternator will be enough to feed the motor and a small household.

More sophisticated systems use a "full wave bridge" rectifier. These take both "good" flow and "bad" flow and make them both good. These, amazingly, use four (4) diodes, so, as you can imagine, you get four times the power as with a single diode. A small system like this will power itself, plus four households.

... you write "to produce electricity, instead of diesel engine".

I can understand that it may be hard to run your TV if diesel engines are coming out of your wall outlets. But a diesel engine is worth a lot of money, whereas enough electricity to run a TV for even 10 hours is only pennies worth.

If I had a contraption that would produce either diesel engines or electricity, I'd go for producing the engines.

Dear Mr. bsnegi91,

The answer for your question is YES - theoritically. But the Alternator Power Supply Frequency will be LESS, depending upon the SLIP of the driving motor, and hence the motor driven by the Alternator speed will be FURTHER less. Energy Conversion Losses will be more.

Motor Efficiency x Generator efficiency = Over-all Efficiency.

DHAYANANDHAN.S

This thread was over 2-1/2 years old, as was the last post from the OP...

I think he is not going to see it.