Compressor motor keeps burning out
Compressor motor keeps burning out
(OP)
I have burned out two compressor motors in a very short period of time and want to know if anyone has any ideas on what to check, I would greatly appreciate the help.
The compressor motor is a Leeson Air Compressor Electric Motor — 5SPL HP, Model# 116845. I replaced the motor about 3 weeks ago and it the second motor to go out withing a short time period. I have checked my connections and everything appears to be up to par.
I have tested the wall receptacle and it is putting out approximately 120v per side of a single phase outlet. I have also tested the power to both sides of the switch and at the motor to ensure it is receiving power. The compressor pump also spins normally, so I do not think it is overworking the motor.
I would greatly appreciate any input.
The compressor motor is a Leeson Air Compressor Electric Motor — 5SPL HP, Model# 116845. I replaced the motor about 3 weeks ago and it the second motor to go out withing a short time period. I have checked my connections and everything appears to be up to par.
I have tested the wall receptacle and it is putting out approximately 120v per side of a single phase outlet. I have also tested the power to both sides of the switch and at the motor to ensure it is receiving power. The compressor pump also spins normally, so I do not think it is overworking the motor.
I would greatly appreciate any input.





RE: Compressor motor keeps burning out
RE: Compressor motor keeps burning out
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Compressor motor keeps burning out
The unloader valve is working as it is supposed to. The compressor is cutting out at it's pre set 120psi as advertised.
RE: Compressor motor keeps burning out
This may sound odd to some of you. But I have seen so many different distribution schemes all over the world that I am prepared to accept the weirdest things.
What part of the world are you in?
Gunnar Englund
www.gke.org
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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...
RE: Compressor motor keeps burning out
What type of starting this motor has? May be the start winding remains in the circuit, which it should not.
Rafiq Bulsara
http://www.srengineersct.com
RE: Compressor motor keeps burning out
A lot of small compressors are only rated intermittent duty, able to run perhaps a few minutes at a time and expecting to be off at least half the time. Is yours rated continuous duty? Is it running for long periods?
Also you state the voltage. At this point you have to measure the voltage at the motor with the compressor actually running.
Does the motor have a start capacitor and a centrifugal switch in it or does it have an external start relay?
The replaced motor came with another start capacitor didn't it?
When does the motor fail? As it's running merrily along or during a start?
Keith Cress
kcress - http://www.flaminsystems.com
RE: Compressor motor keeps burning out
Just because you read the correct voltage at the receptacle when nothing is plugged into it and running, doesn't mean you have enough power available at that receptacle. A very common occurrence is that the load is too heavy for the size of wire you have running to the receptacle and it is causing a voltage drop as soon as the current starts to be drawn by the compressor. That motor draws 15A at 230V when fully loaded. If you have 14ga wire running to your receptacle, that may be fine as long as the run length is short and there is nothing else running on that wire at the same time. But if it is part of another circuit with other loads, and/or the distance is over a few yards, voltage drop may be causing your motors to burn up. Even with heavier gauge wire, the starting current may be so high that it causes an immediate voltage drop and the motor is never getting to full speed, so it ends up running on the starting capacitors the entire time, which would also affect a premature death.
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RE: Compressor motor keeps burning out
Consider getting rid of that 36 pound, 15 amp, "5SPL" HP rated motor and installing one that is actually "5" HP (It will probably weigh considerably more and draw more than 15A).
RE: Compressor motor keeps burning out
I will make sure to check voltage with the motor running when the new motor arrives.
When this motor arrived, I had immediately noticed it was smaller and lighter than the original. It is still under warranty, and I will see if I can upgrade as opposed to direct replacement.
Thank you all for your input.
RE: Compressor motor keeps burning out
RE: Compressor motor keeps burning out
Also, when installing, carefully check the internal connections; 115/230 V motors may come from the factory connected for 115 V, or may come connected for 230 V. The actual connection must match the applied voltage; wrong in either direction results in smoke.
A note on usage: The SPL motors use a part of the overload capacity inherent in a general purpose motor as part of the predicted load cycle. What would normally be marketed as a 2 HP motor can thus be called a 5 HP motor. It can produce 5 HP, for only for a very limited time. Because an air compressor has a load that increases toward the end of the cycle, under normal circumstances the motor only needs to produce the 'rated' 5 HP for a few minutes.
However, if one is heavily using a small air compressor so that it runs continuously, the compressor remains continuously in the end-of-cycle state where the actual load has risen to the 5 HP level, so the motor is forced into overload conditions (remember that it is really a 2 HP motor...) on a near continuous basis. No surprise that motor life is negligible.
RE: Compressor motor keeps burning out
I don't know what SPL means (splashproof?) but I wouldn't read too much into the current rating of a single phase motor... can vary widely depending on things like whether there are some caps that remain in the circuit while running.
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(2B)+(2B)' ?
RE: Compressor motor keeps burning out
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(2B)+(2B)' ?
RE: Compressor motor keeps burning out
Maybe it's a 3450 rpm replacing a 1725?
That would do it!
RE: Compressor motor keeps burning out
SPL means "Split Phase" as opposed to Cap-Start/Cap-Run or PSC. Split Phase motors have relatively low starting torque, so they MUST be used with an unloader on a compressor, otherwise they stall really easy. As to whether or not it is truly "5HP", that's a subject of much debate when it comes to consumer products. Mfrs get away with a lot of "poetic license" when it comes to marketing statements. SPL motors have high breakdown torque, which means if you measure the speed and torque AT THAT MOMENT, it likely calculates out to be 5HP, if only for a very brief time.
I just noticed a potential subtlety in the way you worded this: It sounds like maybe you are describing the pressure switch. The unloader valve is different. Typically on small consumer type compressors like this the pressure switch is what would cut out at 120PSI (if that's where it's set), and kill power to the motor AND THE UNLOADER VALVE. When that happens, the unloader should open and you will hear a brief "Pssssss" noise as the cylinder pressure releases. Then when the pressure switch calls for the compressor again, the unloader stays open for a second or two so that there is no pressure in the cylinder head until after the motor gets to full speed. On larger industrial high volume compressors, the motor runs basically all the time and the unloader cycles on and off to charge the pressure vessel.
If the compressor motor turns on and off via the pressure switch, and the unloader is not working like I stated above, that may be the root of your problems.
"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> FAQ731-376: Eng-Tips.com Forum Policies
RE: Compressor motor keeps burning out
I doubt the original motor was a 1750 rpm, just because we had a compressor with the SPL hp 3450 rpm motor, but I was saying a 3450 replacement of an OEM 1750 motor of similar hp would not last long without a pulley ratio change.
RE: Compressor motor keeps burning out
http://www.wisedan.com/aircomp
Thanks
RE: Compressor motor keeps burning out
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