Baldor motor overheating

[MstrCarpenter]

Trying to get a saw working again. It has a Baldor 5hp. 230v (L3608TM) that overheats even with no load at all. It starts right up but trips the thermal switch within 45 seconds; and yes the motor is hot. I checked the wiring configuration and connections. They are correct according to Baldor for that specific motor. It has a bank of 3 caps. (Different ratings, but Baldor states that may be correct.) My last thought at quitting time was that a starting switch may not be dropping out. It does sound like a rotary phase convertor when the starting caps are left connected too long. Almost like the bearings are trashed, but even though the armature spins a little too easily for my liking, I cannot observe any play.

Has anyone dealt with a similar issue of overheating and/or worked on the start switch on these motors?

[Philip1231]

I'll toss this idea out there: if its not the centrifugal switch keeping the start winding engaged, could it be the number of times the motor is started in a short period of time. If you are trouble-shooting the motor, could it be that frequent starts/stops are leading to excessive heat buildup? Some motors have a specified limit for number of starts per hour. Just a thought.......

[Roly]

Trying to get a saw working again. It has a Baldor 5hp. 230v (L3608TM) that overheats even with no load at all. It starts right up but trips the thermal switch within 45 seconds; and yes the motor is hot. I checked the wiring configuration and connections. They are correct according to Baldor for that specific motor. It has a bank of 3 caps. (Different ratings, but Baldor states that may be correct.) My last thought at quitting time was that a starting switch may not be dropping out. It does sound like a rotary phase convertor when the starting caps are left connected too long. Almost like the bearings are trashed, but even though the armature spins a little too easily for my liking, I cannot observe any play.

Has anyone dealt with a similar issue of overheating and/or worked on the start switch on these motors?

Most likely cause is the switch or start cap.  Take the end bell off (mark orientation first ) clean and make sure the parts all move easy especially the collar that actually operates the switch.
 I don't have that exact motor but most are basically the same Roly

[MstrCarpenter]

I tested the caps; all three are within the 6% parameters. I removed the fan and one motor end to access the centrifugal switch. This motor has a zerk fitting at both ends and there was a lot of excess grease in and around the switch. I couldn't get the rotor out without a puller. Who knows if, or how much crud is packed between the rotor and stator. Obviously with a TEFC motor there's no way of knowing how much is enough vs. too much. I'll clean it all up and reassemble, with new bearings if I have them.

That's about how far I got today. At least I now know which wires go to the switch. After it's assembled, I can confirm the contact are closed with a simple continuity test. How do I (safely) test or confirm the contacts are open or closed while it's running? I'm a little apprehensive of putting probes on energized and functioning caps so I need some expert advice. I'd much rather not fry a meter nor myself in the process.

[Roly]

I tested the caps; all three are within the 6% parameters. I removed the fan and one motor end to access the centrifugal switch. This motor has a zerk fitting at both ends and there was a lot of excess grease in and around the switch. I couldn't get the rotor out without a puller. Who knows if, or how much crud is packed between the rotor and stator. Obviously with a TEFC motor there's no way of knowing how much is enough vs. too much. I'll clean it all up and reassemble, with new bearings if I have them.

That's about how far I got today. At least I now know which wires go to the switch. After it's assembled, I can confirm the contact are closed with a simple continuity test. How do I (safely) test or confirm the contacts are open or closed while it's running? I'm a little apprehensive of putting probes on energized and functioning caps so I need some expert advice. I'd much rather not fry a meter nor myself in the process.

If you don't have one get a cheap clamp on ammeter,   the amperage should drop off quickly after starting and be well less than full load current.    Since the caps are good it must be the switch.    Clamp on to one or the 240v leads, probably by the starter contactor.  If there is that much grease around it that is probably the issue.    I doubt if grease between rotor and stator is a issue with a 5 hp motor but than much grease by the centrifugal switch would prevent it from moving.   See if removing the other end bell will allow the rotor to come out to clean it up, should not have grease in that area.  Roly    (remember to mark orientation on this end also)

[MstrCarpenter]

Thanks Roly! That never dawned on me, even though I use it frequently to balance loads on 3ph power. I just studied the schematics for the motor and it appears that the centrifugal switch only drops the current to the "electrolytic cap"; the "oil cap" stays connected, in series, to the start winding. So now I also have to check that the correct caps are being dropped. IIRC there's one around 26 mfd and two in parallel around 60 mfd. Can I assume the lower rated one is for running?

I wasn't aware that Fluke made a "cheap" clamp-on meter. 
 I am interested in getting one that will measure very low D.C. current to help isolate some phantom battery discharges. Today it was the alternator in a Yale forklift. It still charged, but took back every bit of it in three days. On another machine, it was insect nests behind the fuse block.

[Roly]

Thanks Roly! That never dawned on me, even though I use it frequently to balance loads on 3ph power. I just studied the schematics for the motor and it appears that the centrifugal switch only drops the current to the "electrolytic cap"; the "oil cap" stays connected, in series, to the start winding. So now I also have to check that the correct caps are being dropped. IIRC there's one around 26 mfd and two in parallel around 60 mfd. Can I assume the lower rated one is for running?

I wasn't aware that Fluke made a "cheap" clamp-on meter. 
 I am interested in getting one that will measure very low D.C. current to help isolate some phantom battery discharges. Today it was the alternator in a Yale forklift. It still charged, but took back every bit of it in three days. On another machine, it was insect nests behind the fuse block.

Fluke does not make cheap meters, they are my go to meters.      There are very cheap clamp ammeters (harbor Freight)  that would show it if you didn't have one.    The 26 mfd would be running cap.  The schematic may show which cap is which.    I am still betting on a gummed up switch.   Was this motor running before or did you just get it ?  If it was running before don't switch things around yet.    I think the part of the centrifugal weights that move to operate the switch are stuck or the contacts are welded together.     I don't know about low current DC clamp ammeters.   I have never tried to put turns of wire on the clamp on DC like you can on AC to change the sensitivity,   I will have to try it sometime.  Roly

[MstrCarpenter]

Fluke does not make cheap meters, they are my go to meters.      There are very cheap clamp ammeters (harbor Freight)  that would show it if you didn't have one.    The 26 mfd would be running cap.  The schematic may show which cap is which.    I am still betting on a gummed up switch.   Was this motor running before or did you just get it ?  If it was running before don't switch things around yet.    I think the part of the centrifugal weights that move to operate the switch are stuck or the contacts are welded together.     I don't know about low current DC clamp ammeters.   I have never tried to put turns of wire on the clamp on DC like you can on AC to change the sensitivity,   I will have to try it sometime.  Roly

I can check them at the caps with everything assembled except the cap housing.

Neither schematic nor parts list indicate cap rating (only that there's a bank of two or more).

The only info. I got was "It needs a new motor". Judging from the amount of grease packed into it, I'm not overly confident in the abilities of the previous owner. (The only thing I did before energising it was verify the connections were correct at the service cord/junction/thermal switch Box)

I don't plan on changing anything unless it's obvious. (I too pic.s before and during)

The contacts are not burnt or stuck together, and I can't physically see the weights in operation.

I had never heard of this before. Now's a good a time as any to "Google it". Just watched a vid. of a guy doing it to test amperage of AA batteries, so it's at least possible in the 3-4 amp range. He was dead shorting the terminals with the only resistance being about 3' of 22-18 ga wire. Not surprisingly, the amperage dropped with each successive test. Probably not the best way to check if your batteries are still good.

[Roly]

I can check them at the caps with everything assembled except the cap housing.

Neither schematic nor parts list indicate cap rating (only that there's a bank of two or more).

The only info. I got was "It needs a new motor". Judging from the amount of grease packed into it, I'm not overly confident in the abilities of the previous owner. (The only thing I did before energising it was verify the connections were correct at the service cord/junction/thermal switch Box)

I don't plan on changing anything unless it's obvious. (I too pic.s before and during)

The contacts are not burnt or stuck together, and I can't physically see the weights in operation.

I had never heard of this before. Now's a good a time as any to "Google it". Just watched a vid. of a guy doing it to test amperage of AA batteries, so it's at least possible in the 3-4 amp range. He was dead shorting the terminals with the only resistance being about 3' of 22-18 ga wire. Not surprisingly, the amperage dropped with each successive test. Probably not the best way to check if your batteries are still good.

The weights are what most likely the problem, because if they cant move they will not open the switch when up to speed.   Roly

[Roly]

Did you ever make any headway with the motor ?  Roly