SMC 3 soft started motor wont start.

[einnh]

I have a 20hp/460VAC/60Hz motor on a SMC3 soft starter. I have used several of these in the past on previous projects. I have had them go bad in the past but they would at least fault first.

I have a NEW install I am doing now and just went to power up the motor and am not getting any response. I double checked the wiring in the motor box as well as for hte SMC...the SMC 3 turns on (LED illuminated) but the motor doesn't spin and there are no fault codes. There is 470VAC power on the input and I am seeing an oscillating voltage on the output.

 

[jraef]

Is the motor connected? If there is a local disconnect switch, is it left open? A soft starter will not turn on if there is no motor.

 

[swimmy67]

Check the dip switches. AB made changes to the dip switch settings from the older SMC-3 motor starters. What worked before will not work with the new dip switch settings.

 

[einnh]

I'll go double check the dip settings.

So here is more detail. 20hp 3 phase AC motor on a 37A SMC-3 by Allen-Bradley. Motor is coupled to a hydraulic pump. System is started with control valves in open position for minimal resistance.

• Checked incoming power. ~460VAC inter-phase and ~265 PE.
• I megged the motor. Everything checks out between phases and phase to ground. Megged 1000V through the supply cable.
• Checked the incoming and outgoing power leads. All are secure.
• I checked that the leads are wired correctly inside the motor box.
• I disconnected all the 24v input control leads and used a bench power supply.
  • A1 +24VDC
  • A2 Com
  • In1 +24VDC to start
  • In2 drop 24VDC to stop.
  • Rest aren't connected for testing.
• Turned on power supply. Device LED turns on which says it is running. Nothing is happening with the motor. (LED would flash with a code if there was a fault or error).
• Monitoring the output power leads I am seeing 0 - 300VAC oscillating.
• Swapped the device (which is brand new) for another new device (spare). Same result.

It has to be something stupid. I can't figure out what it is. Of course Rockwell Tech Connect is on lunch. (Why do I pay these guys for a contract I can never reach them!)

 

[einnh]

My current settings are:



I have tried switching to soft-start from current limiting as well as increasing the overload. That did not work. And if the device had overloaded it would have shown an error flash.

 

[einnh]

I found the new dip-switch settings but am not sure which model they apply to or which model I have.

I have two different documents for dip switch settings and they both say Series B.

 

[einnh]

Got a hold of Tech Connect. The new dip settings should work. going to try now.

Annoying that I have two documents for Series B soft starts with different dip settings.

 

[einnh]

New dip switch settings worked. ... very annoying.