Single Phase Two Speed Motor Only Runs in High Speed

[mcglm]

I am using a 230vac two speed motor and recently took the two speed timer off and installed a single pole double throw three position switch according to the suppliers directions. I turned the thing on and due to my not having everything secured it arced near the wiring terminations. I immediately shut it down, properly secured and restarted. It then ran in high speed only. I determined the switch was bad and replaced it.Upon doing so it ran in both speeds for a short period of time but upon restart it only ran in high. I then completely disconnected the switch and it it now runs but in high only. Weird. Any ideas?

 

[btrueblood]

You probably arced the one switch once again. You may need a higher amp rated switch, or you may need a "break before make" function between the two switches.

 

[mcglm]

Thanks for the quick suggestion. I checked the amp rating on the switch and it was OK for this application and it had an 'off' position between the other two positions. There's only one switch and I was VERY careful in my install however I'll try another switch. I'll let everyone know how this works out because it's a mystery to me unless I'm missing something with these single phase two speed motors.
THanks

 

[ScottyUK]

When you say that the switch has adequate rating for the motor, does it have adequate rating for switching the high starting current which occurs when starting a motor? The starting current for a single phase motor can be up to 8x running current, depending on the type of motor, and persists until it reaches running speed.


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If we learn from our mistakes I'm getting a great education!

 

[LionelHutz]

The switch should have an appropriate HP rating if it's capable of starting the motor. Or else use a switch rated for about 8 times the rated motor current.

 

[waross]

We generally look for a switch with an adequate Horse Power rating. Amp rating alone doesn't cut it for motor service.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[mcglm]

Well folks the problem is not the switch as I completely disconnected it and the motor runs on high speed only. I'm now looking for a wiring schematic so I can figure what is causing this. I am guessing a welded relay.