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SINGLE PHASE SOFT STARTER


DEVITG

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It is posible to use a soft starter on a single phase motor ?

 

It is for two semihermetic refrigeration motocompresor , with current relay as start device.

 

The main problem is that it is installed on a truck with a generator .

The full load amp is 9- 11 amps. 220 V 50 Hz.

The generator is a 16 HP briggstraton with a 8 KVa.

It can start and run only one , but it will not star the second unit.

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Hello devitg

 

Yes it is possible to use a soft starter on a single phase motor.

It needs to be a single phase soft starter, and will work best on capacitor start motors. From my experience, soft starters do not work as well on induction start motors.

Unfortunately, I can not at present suggest a manufacturer of a single phase soft starter.

 

Best regards,

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  • 2 weeks later...
Guest DEVITG01

It is for two semihermetic refrigeration motocompresor , with voltimetric relay as start device.

160 mF Start capacitor

65mF Run Capacitor

 

 

The main problem is that it is installed on a truck with a generator .

The full load amp is 9- 11 amps. 220 V 50 Hz.

The generator is a 16 HP briggstraton with a 8 KVa.

It can start and run only one , but it will not star the second unit.

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  • 3 years later...

Hi,

 

I resurrected this thread only because the subject of soft starting single phase motors came up for me recently, and I stated that you could NOT start a cap-start motor because of the problems of having capacitors down stream of the SCRs. The motor manufacturer contradicted me and in searching for support information, I read this. Now I am wondering if I was wrong (horror of horrors!) How is it that the starting capacitors are not a problem on 1 phase motors? Is it because the motor winding inductance in in series with it?

"He's not dead, he's just pinin' for the fjords!"
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Hello jraef

 

I have soft started many single phase motors with cap start without problems.

You can apply the soft starter to the whole motor (including cap and start winding) or apply the soft starter to the run winding only.

My preferred method is to the run winding only as you get a greater reduction in start current.

I have not had any issues with either the capacitors failing, or the soft starter failing due to the capacitor.

The only single phase motors that I will not soft start are induction start. (no capacitor) as they rely on iron saturation effects and just do not perform with soft starters.

 

Best regards,

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Care must be taken, ie in cases where the start voltage is set so low that the motor labours we have experienced problems with the capacitors and on fewer occasions, the centrifugal switch.

 

Another issue is that of 480V single phase motors intended for SWER line applications. These generally comprise 2 x 240V windings connected in series, the caps are also 240V rated. Through a simple voltage divide you will find that if the start voltage is set below 50%, the capacitor will experience an overvoltage condition until the voltage ramps above that point. capacitors can and do fail quickly under this condition.

 

In the main however, applying single phase soft starters to cap start or cap start cap run motors with flly rated windings and capacitors does not present an issue. There are companies established throughout Australia that literally sell thousands of them for use in domestic and light commercial air conditioning systems. Another common application particularly throughout WA is bore pumps.

 

Regards,

GGOSS

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