# ac motor and voltage



## major (Apr 4, 2008)

67gtman said:


> I am wondering what would happen with an AC (induction) motor if supplied with double voltage for what it is designed. E.g. supplying the motor designed for 110V/50 Hz with 240V/50 Hz current, both single phase.


Hi gtman,

Chances are it would saturate, draw lots of current and take out the circuit breakers or fuses.



> Does the same apply to DC motors?


No. Depends on the type of motor on what would happen. Most EVs use series wound DC motors which would run on double voltage at twice speed, and do O.K. depending on the particulars, like the armature being able to physically withstand the higher RPM.

Regards,

major


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## 67gtman (Dec 12, 2008)

Thanks for the reply. So for AC/induction motors: if the motor takes e.g. 10 amps at 110 V, it would take the same 10 amps at 240 V? Does this increase just electric bill or affects somehow the motor's reliability? (not quite understand what happens when motor saturates)

How can you control amps being drawn by the motor?


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## major (Apr 4, 2008)

67gtman said:


> Thanks for the reply. So for AC/induction motors: if the motor takes e.g. 10 amps at 110 V, it would take the same 10 amps at 240 V?


Hi gt,

I don't quite understand. What I said, or tried to relate, is that if you apply double rated voltage to an induction motor at rated frequency, it will draw excessive current.



> Does this increase just electric bill or affects somehow the motor's reliability? (not quite understand what happens when motor saturates)


Likely the motor would burn up shortly from excessive current and other losses. Saturation is when the iron in the motor is driven beyond its limits. Result in this case is drastic decrease in reactance and excessive current draw.



> How can you control amps being drawn by the motor?


Either use the rated voltage or an inverter drive which will control the voltage/frequency relationship.

Regards,

major


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## 67gtman (Dec 12, 2008)

This may be trivial for you I guess, sorry for bothering, just wondering if there is any simple modification to do to the 110V motor to use it without transformer on let's say 240V current. What would be needed in such conversion?


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## frodus (Apr 12, 2008)

simple modification:
rewind the motor coils so the coils accept 240

thats about all you can do


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## major (Apr 4, 2008)

67gtman said:


> This may be trivial for you I guess, sorry for bothering, just wondering if there is any simple modification to do to the 110V motor to use it without transformer on let's say 240V current. What would be needed in such conversion?


A lot of induction motors, including single phase, have dual voltage windings. Inside the conduit box is the connection diagram for each. I just bought a well pump motor which actually has a switch inside the cover for 115/230 VAC. It is 1/2 HP single phase, 60 Hz.

If the motor is not dual voltage, then you'd have to reconnect the coils inside or basically rewind. Most single phase motors are 3 HP or smaller and pretty cheap, so you'd probably be ahead just getting the proper motor to start with. Or like you say, get a transformer.

And what does this have to do with EVs? 

Regards,

major


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