AC Single Phase Motor Starter

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Hello,

 

Is it safe to regularly on off a AC induction motor?. around 10 second interval

it is possible to use SSR to start the motor instead of contactor ?

~ Chandana ~ a self learner

Last Edited: Tue. Nov 4, 2014 - 09:53 AM
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The motor might get a bit warm doing this. A solid state disk (SSD) might not help. i gather you mean a Solid state relay (SSR).  I'd be asking the motor manufacturer and telling him what sort of load is involved.

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typing mistake. it's SSR
 

~ Chandana ~ a self learner

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is it speed control or power save ?

 

If you use SSR don't talk about 10 sec, but down to 10 50Hz periods.

Make sure you get a SSR that only do something at the zero crossings (to avoid switching noise) .

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The motor should be fine as long as it can handle the load / duty cycle.

 

A good solid state relay will have no problem as sparrow said, you can duty cycle the thing :)

I used to run 3 phase hydraulic pumps with them. Granted they were on / off but they outlasted the mercury contactors.

But again these were the big heavy duty ones 50(?) amps per phase or so

Keith Vasilakes

Firmware engineer

Minnesota

Last Edited: Tue. Nov 4, 2014 - 03:51 PM
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You really can't compare starting three-phase motors with starting single-phase motors since three-phase motors are inherently self starting while single-phase motors are not. 

 

The OP did not mention which type of single-phase motor he is dealing with.  If it is a 'split phase' motor it will have a separate 'starting winding' that is not designed for continuous (or rapidly repeating) use, hence the need to consider duty cycle.  This starting winding has higher resistance than the main running winding thus producing more heat, hence the need to consider warming.

 

Don
 

Last Edited: Tue. Nov 4, 2014 - 03:24 PM
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motor windings have  same resistance. motor used for star-wheel of a bottle filler.

first i run the motor continuously and used mechanical clutch to engage the wheel in each 10 second. and motor burned out in few hours 

~ Chandana ~ a self learner

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I'd be finding out why the motor burnt out first up. Maybe it is not large enough for the task? An engineer would calculate the power required then select a suitably sized motor.

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first i run the motor continuously and used mechanical clutch to engage the wheel in each 10 second. and motor burned out in few hours 

 

 

If the motor burned out  in a few hours when loaded via a clutch,  it will burn out within 15 minutes if constantly stopped started under similar load cycle conditions

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ignoramus wrote:

first i run the motor continuously and used mechanical clutch to engage the wheel in each 10 second. and motor burned out in few hours 

 

If the motor burned out  in a few hours when loaded via a clutch,  it will burn out within 15 minutes if constantly stopped started under similar load cycle conditions

 

Agreed.

If that is your application the clutch is the right way to do it.

Get a bigger motor

Keith Vasilakes

Firmware engineer

Minnesota