Synchronous compressor motor fails to get up to speed 1

[oftenlost]

Surplus 250 HP, Westinghouse synchronous, 514 RPM, 440 volts, 261 AMPS FLA. Procured and inspected by service shop, good megger, surge test, rotor drop test and amortisseur appears to be original. Lead markings, 2 each of 1,2 and 3. XLE compressor with rotor on compressor crank
Installed and start attempted. Original GE 14 ohm resistor across rings. Motor accelerates to 250 to 260 RPM and hangs there. Start current 600 AMPS. Compressor unloader checked OK. Start resistor taken up in steps 18, 21 and then 26 with no apparent effect on speed. No arcing at rings or amortisseur. Talked to used motor vendor who indicated that he removed the motor personally from an idled plant site and had used the compressor for other purposes.

 

[waross]

I'm impressed, JRaef.
Respectfully

 

[oftenlost]

jraef,
That is the animal in question. I have only been out on these maybe 10 times in my 48 years of "fixin broke stuff" although we have repaired numerous units in our shop. Most of the plant visits have been ring, brush or squirrel cage protection shutdowns so I have never become really knowledgable of the beast. As the OEM shop closest to the IR manufacturing facility in North Carolina while they were still in production, we got the lion's share of the warranties and shipping damage claims.
I am truly appreciative of all the responses and ideas offered here. I will follow up and keep the forum appriased of progress. Thank you.

 

[itsmoked]

How come reverse operation doesn't toast all the bearings?? Reversed oil pump and all..?

BTW: Nice catch jraef!

Keith Cress
Flamin Systems, Inc.-

http://www.flaminsystems.com

 

[DaveScott]

jraef, thanks.

 

[swn1]

Hang a good power monitor on the circuit and record kW plus kVAR or kVA or PF during a start. If the problem is torque you'll see high real power. Reactive power will give you an indication of back emf evolution. If there is something exotic wrong with the windings you'll see it on the waveform capture.

Also, the field discharge resistor value does have an influence on the starting torque. Not an issue when starting a sync motor unloaded or partly loaded but we've seen problems with big motors trying to start at rated torque. I can't imagine it being a factor on the little XLE motors, though.

I was not aware of the XLE rotation quirk, I've worked on quite a few medium voltage XLE starters but hadn't encountered that. Learn something every day.