Wire this variac up correctly

  • Thread starter bicc
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anyone point me in the right way to wire this variac up correctly....i'm wanting to control the speed of a fan running at 240v
 

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Averagesupernova

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Re: variac

What type of motor does the fan use? You may not be able to it at all.
 
2
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Re: variac

howdy Averagesupernova

its a ruck fan 6"
power 95w
voltage 230v
amp 0.45
 

Averagesupernova

Science Advisor
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542
Re: variac

If it is not a universal motor capable of running on DC it will not work.
 
880
98
Re: variac

If it is not a universal motor capable of running on DC it will not work.
AC induction motors will work just fine with variacs. I know this for a fact because I once worked for a manufacturer of AC induction motors. We used variacs all the time for powering and testing the motors.

Connect incoming power to terminals 2 and 5. Connect the motor to terminals 2 and 3.

Edit:
AC induction motors do not speed regulate very well without a variable frequency drive. Depending on the motor, it may be possible to get some speed regulation, but it will be inefficient and the motor may get hot.
 
Last edited:

Averagesupernova

Science Advisor
Gold Member
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542
Re: variac

Edit:
AC induction motors do not speed regulate very well without a variable frequency drive. Depending on the motor, it may be possible to get some speed regulation, but it will be inefficient and the motor may get hot.
No way. A huge advantage of AC induction motors is that they regulate speed quite well at a set line frequency. Any induction motor I have seen that is run at line frequency (60 hertz) and reduced voltage will draw more current and heat up. The motors I have experience with a multiple horsepower, not a fractions of fractions like a small fan motor.
 
880
98
Re: variac

Most small fan motors are shaded pole motors. They have the disadvantage of low starting torque and very low efficiency, even at their designed operating voltage. But they also have the advantage of allowing some speed control below the synchronous speed. There normal operating speed is around 10% below synchronous.

The best I can tell from my google searching, the Ruck 6" motor is NOT a shaded pole motor. Therefore, I would not recommend using it with the variac as a speed control. Doing so would probably exceed the ratings of your variac and cause your motor to run hot.

Edit:
Averagesupernova, when I said ac induction motors do not speed regulate very well, I was referring to the fact that it is difficult to regulate the speed by varying the voltage. I can see how the sentence could be misinterpreted. Poor wording.
 
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