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Single Phase Two Speed Motor Only Runs in High Speed

Single Phase Two Speed Motor Only Runs in High Speed

Single Phase Two Speed Motor Only Runs in High Speed

(OP)
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?

RE: Single Phase Two Speed Motor Only Runs in High Speed

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.

RE: Single Phase Two Speed Motor Only Runs in High Speed

(OP)
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
 

RE: Single Phase Two Speed Motor Only Runs in High Speed

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.
  

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

RE: Single Phase Two Speed Motor Only Runs in High Speed

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.
 

RE: Single Phase Two Speed Motor Only Runs in High Speed

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

RE: Single Phase Two Speed Motor Only Runs in High Speed

(OP)
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.

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