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Air Compressor Problem - Motor Stalls
From the original post that started this thread: ... underpowered - it pumps up to about 95 psi ok, but then the motor stalls. The unloader bleeds the pressure off, the motor restarts, runs for a couple of seconds, and then stops again...repeat...repeat..." Yes, those're the symptoms. So it stalls first, then the unloader bleeds off pressure at the compressor and allows it to restart? I'm puzzled, but at this point I would disable the switch and unloader and see if the compressor runs up to 120 as it used to. You said the motor current is only 5 or 6 amps when it stalls? Locked-rotor current for a 1/3HP motor should be much more than that, at least 30 amps (I haven't looked it up). You're sure it's getting full line voltage at that point? I don't see how it could be. Alan |
Air Compressor Problem - Motor Stalls
On Mon, 08 Mar 2010 01:04:59 GMT, lid (Sparks
Fergusson) wrote: PeterD wrote: Typical small compressors the unloader opens when the pressure switch activates and shuts off the compressor. This releases all pressure on the compressor head, allowing the motor to start when pressure drops down to the cutin PSI. On this compressor, the check valve/unloader is completely separate from the pressure switch. The unloader is similar to this one: http://www.amazon.com/Control-Device...nloader-Check/ The URL above is 'dead'... This is probably what you are trying to point to: http://www.amazon.com/Control-Device...8055829&sr=8-1 IHMO it has not been said that the motor is stalling! A stalled motor (called locked rotor) will cause input current to swing sky-high, usually tripping the breaker, making a hell of a noise, and is very obvious. The voltage to the motor is never interrupted during the stop/start cycle. Above a certain psi (about 95), the motor starts bogging down and eventually stops. This occurs even if I bypass the pressure switch and attach the cord directly to the motor leads. Then, after the unloader vents the pressure, the motor will restart. So the motor actually stalls, and there are no sounds (humming, etc.) from it? Input current does not swing sky-high, though, nor does the breaker trip, nor is there a hell of a noise. It definitely comes to a dead stop, though. A most interesting set of symptoms... Motor stalls to locked rotor, no significant current draw, odd... How 'hot' is the motor? Is it possible the thermal cutout is tripping (at too low a temperature, perhaps?) |
Air Compressor Problem - Motor Stalls
On Sun, 07 Mar 2010 21:56:03 -0500, Alan Douglas
wrote: From the original post that started this thread: ... underpowered - it pumps up to about 95 psi ok, but then the motor stalls. The unloader bleeds the pressure off, the motor restarts, runs for a couple of seconds, and then stops again...repeat...repeat..." Yes, those're the symptoms. So it stalls first, then the unloader bleeds off pressure at the compressor and allows it to restart? I'm puzzled, but at this point I would disable the switch and unloader and see if the compressor runs up to 120 as it used to. You said the motor current is only 5 or 6 amps when it stalls? Locked-rotor current for a 1/3HP motor should be much more than that, at least 30 amps (I haven't looked it up). You're sure it's getting full line voltage at that point? I don't see how it could be. Alan Well, he did say (in another post) he's bypassed the pressure switch for a test run, and the symptoms persist. I think he's got a high resistance point in the wiring too, but I'm not sure where. Maybe monitor voltage at the motor terminals might give a clue. As Alan says, locked rotor should result in very high current/power draws. It is very noticable, and unless the compressor is on a circuit that is vastly overfused result in a blown fuse/tripped breaker almost immediately. Can you (the OP) post specicifications from the motor's name plate, and the compressor assembly? FWIW, no compressor has a fractional HP motor, most are motors rated at 1 to 3 HP on small compressors. |
Air Compressor Problem - Motor Stalls
Sparks Fergusson wrote: I only see one capacitor, so I'm assuming it's in the starting circuit. I don't have a wiring diagram, and GE has no information on it's website for this motor. Don't assume. What is the capacitance? Some small split phase motors only have a run capacitor. The fact that the current only rises slightly indicates a bad capacitor or a poor connection to one winding. -- Greed is the root of all eBay. |
Air Compressor Problem - Motor Stalls
In article , "Michael A. Terrell" wrote:
Sparks Fergusson wrote: I only see one capacitor, so I'm assuming it's in the starting circuit. I don't have a wiring diagram, and GE has no information on it's website for this motor. Don't assume. What is the capacitance? Some small split phase motors only have a run capacitor. The fact that the current only rises slightly indicates a bad capacitor or a poor connection to one winding. I don't think GE is making the motors anymore, and thats why you can't get info. Either test the cap or replace it. Its probably a run cap. greg |
Air Compressor Problem - Motor Stalls
The main problem is that the motor is being overloaded. As mentioned
already, induction motors don't get tired or exhibit lower power output with age. You don't state some of the most essential info.. namely, the brand name and model number of the air compressor, and the size and type of air pump. The complete info listed on the motor label should also be included. We can't see it from where we are. Forget the capacitor.. the motor is starting normally, so the cap isn't the problem. A mechanical failure in the motor may be contributing to the overload. The motor bearings may be worn out, they're likely to be sleeve bearings in a 1/3 HP motor, and not replaceable, but all hope is not lost if the motor shaft isn't scored. FWIW, sleeve bearings can wear to the extent that the rotor begins to rub on the stator segments (lots of friction and excess heat). If the bearing surfaces aren't completely wiped out, re-orienting the end bells of the motor may provide better bearing surfaces. If the bearings are the sleeve type, and haven't been oiled regularly, it's likely they would be worn or damaged. I can't positively explain why the motor isn't already destroyed, or why the circuit breaker isn't tripping. It's very likely that the overloading of the motor is related to air pressure from the tank resisting movement of the piston in the pump, if the pump is a piston-type pump. Normally on small air compressors, tank pressure is isolated from the piston by a check valve at the tank fitting. Additionally, (in a piston air pump) there are likely to be reed valves in the head of the air pump that would separate the cylinder from the outlet fitting (the tubing constitutes a manifold in air compressor nomenclaure, if the unit doesn't have a separate part designated as a manifold). If the air intake is restricted (or choked off from a clogged filter as many small air compressors only have a piece of wool felt filters), this may contribute to more load on the motor. Many piston air pumps have oil lubrication in the pump's case. If the oil becomes very dirty or the level is inadequate, bearings, the pison and cylinder can be damaged, resulting in excess friction until a full failure takes place. It's possible that the motor's thermal protector is responding to high current, and if this is the case in this particular situation, it's the reason the circui breaker hasn't tripped, and likely saved the motor from destruction. It's fairly obvious that the restarting actions described are the result of a self-resetting protective device. With the power cord unplugged, and the belt removed from the air pump (if it's a piston-type pump), the pumping action can be checked by placing a finger over the outlet fitting and briskly turning the pump pulley by hand. The pump's basic operations of intake and compress/ouput can be observed with this fairly simple test. Some of the same conditions included above may pertain to diaphram-type air pumps, although many diaphram types are direct drive, where the motor and pump are a single unit, which may make checking the pump's basic operation a little more difficult. -- Cheers, WB .............. "Sparks Fergusson" wrote in message ... I'm having a problem with my 20 gallon, single stage electric air compressor. It's acting like the motor is underpowered - it pumps up to about 95 psi ok, but then the motor stalls. The unloader bleeds the pressure off, the motor restarts, runs for a couple of seconds, and then stops again...repeat...repeat... snippage Anyone have any ideas? Thanks! |
Air Compressor Problem - Motor Stalls
On Mon, 08 Mar 2010 08:58:34 -0500, PeterD wrote:
On Sun, 07 Mar 2010 21:56:03 -0500, Alan Douglas wrote: From the original post that started this thread: ... underpowered - it pumps up to about 95 psi ok, but then the motor stalls. The unloader bleeds the pressure off, the motor restarts, runs for a couple of seconds, and then stops again...repeat...repeat..." Yes, those're the symptoms. So it stalls first, then the unloader bleeds off pressure at the compressor and allows it to restart? I'm puzzled, but at this point I would disable the switch and unloader and see if the compressor runs up to 120 as it used to. You said the motor current is only 5 or 6 amps when it stalls? Locked-rotor current for a 1/3HP motor should be much more than that, at least 30 amps (I haven't looked it up). You're sure it's getting full line voltage at that point? I don't see how it could be. Alan Well, he did say (in another post) he's bypassed the pressure switch for a test run, and the symptoms persist. I think he's got a high resistance point in the wiring too, but I'm not sure where. Maybe monitor voltage at the motor terminals might give a clue. As Alan says, locked rotor should result in very high current/power draws. It is very noticable, and unless the compressor is on a circuit that is vastly overfused result in a blown fuse/tripped breaker almost immediately. Can you (the OP) post specicifications from the motor's name plate, and the compressor assembly? FWIW, no compressor has a fractional HP motor, most are motors rated at 1 to 3 HP on small compressors. Additional comment. The five amps draw is perhaps normal for this unit, as it appears to be a 240 volt setup. I was thinking it was 120 volt (US) but I appear to be wrong there... g |
Air Compressor Problem - Motor Stalls
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Air Compressor Problem - Motor Stalls
PeterD wrote:
This is probably what you are trying to point to: http://www.amazon.com/Control-Device...8055829&sr=8-1 Sorry, yes, that's the one. So the motor actually stalls, and there are no sounds (humming, etc.) from it? Yes, it actually stalls. There's not super loud humming. There may be some motor noise, but it's hard to hear over the sound of the unloader. A most interesting set of symptoms... Motor stalls to locked rotor, no significant current draw, odd... How 'hot' is the motor? Is it possible the thermal cutout is tripping (at too low a temperature, perhaps?) Well, it does get warm. It gets warm when running with the belt off, too. When it goes into it's stall cycle, it's definitely warmer than that. I can put my Mk I hand on it for about 8 seconds, which says it's hot, but not super hot. |
Air Compressor Problem - Motor Stalls
Alan Douglas wrote:
So it stalls first, then the unloader bleeds off pressure at the compressor and allows it to restart? Yes, that's correct. I'm puzzled, but at this point I would disable the switch and unloader and see if the compressor runs up to 120 as it used to. It's a mechanical unloader, integrated with the check valve, so disabling it would be difficult. However, it's pretty obvious that the unloader only opens after the motor stalls when the check valve closes. You said the motor current is only 5 or 6 amps when it stalls? Locked-rotor current for a 1/3HP motor should be much more than that, at least 30 amps (I haven't looked it up). You're sure it's getting full line voltage at that point? I don't see how it could be. There's definitely no current spike when it stalls, nor does it trip the breaker, dim the lights, etc. Is it getting full voltage? It is at the point the motor leads connect to the pressure switch. I can't easily measure any closer than that because the leads run into the motor and there's no easy way to get to them, especially when it's running. But, it looks like I need to disassemble the motor and check things out inside, so that'll be the next step. Thanks! |
Air Compressor Problem - Motor Stalls
PeterD wrote:
Well, he did say (in another post) he's bypassed the pressure switch for a test run, and the symptoms persist. I think he's got a high resistance point in the wiring too, but I'm not sure where. Yes, bypassing the pressure switch doesn't make any diffence. You may well be right about a high resistance point. Maybe monitor voltage at the motor terminals might give a clue. I can't easily get to the internal terminals. The closest I can measure is at the pressure switch, and the voltage looks fine there. As Alan says, locked rotor should result in very high current/power draws. It is very noticable, and unless the compressor is on a circuit that is vastly overfused result in a blown fuse/tripped breaker almost immediately. It's on a standard outlet circuit with a 20A breaker. It hasn't tripped. Nor have there been any of the signs that you mention for high current draw. Can you (the OP) post specicifications from the motor's name plate, and the compressor assembly? FWIW, no compressor has a fractional HP motor, most are motors rated at 1 to 3 HP on small compressors. 1/3 HP is what's on the nameplate. These days, it would probably be rated at 1 or 2 "marketing HP" :-) The compressor itself has long lost it's label. But, it's a single cylinder reciprocating, belt driven compressor with about a 20 gallon tank, a 3 inch pulley on the motor and a 9 inch on the compressor. The motor was made by GE, and is labeled: Model: 5KC42JG391AX Volts: 115/230 Ph: 1 Amps: 6.0/3.0 HP: 1/3 HZ: 60 RPM: 1725 It's running on 120 volts. |
Air Compressor Problem - Motor Stalls
Meat Plow wrote:
On Tue, 09 Mar 2010 05:57:35 GMT, lid (Sparks Model: 5KC42JG391AX Is that ther right Part #? Does it have some dashes inbetween the numbers and letter like most Ge motors do? No dashes. That's what's printed on the motor nameplate. Is it wired for 120? Yes. |
Air Compressor Problem - Motor Stalls
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Air Compressor Problem - Motor Stalls
David wrote:
The problem turned out to be that wasps had plugged up the air input holes with mud. Cleaned out the mud and away she went Darn mud daubers! Not the issue with mine, though. Thanks! |
Air Compressor Problem - Motor Stalls
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Air Compressor Problem - Motor Stalls
wrote in message ... On Thu, 04 Mar 2010 05:13:31 GMT, lid (Sparks Fergusson) wrote: After reading all the posts, several things stand out. The most significant: There is no excessive current draw when the motor stalls. By all the laws of physics, that is flat out impossible. There are two explanations (well, three, but I'm assuming you aren't making this up). The first is slippage at the belt, motor pulley, or rotor. Given the knowledge you have exhibited, I say that can't be the problem; it's pretty hard to miss the fact that the motor is spinning but the belt is slipping. That leads to only one conclusion: The actual voltage to the windings is dropping. Possible causes are a bad thernal overload protector, bad run capacitor (some motors hide the starting capacitor inside, while the run capacitor is in a cupola on the side), or a corroded terminal so only one of the paired windings is used. All of these possible causes result in a lot of heat generated at one small point EXCEPT the single winding and the bad run capacitor. The single winding explanation is unlikely because it would not deteriorate gradually. That leaves the bad run capacitor. PlainBill There is one more possible cause: Some or all of the windings on the rotor that are supposed to be shorted are open. An induction motor works because windings on the rotor are shorted to induce the field needed to turn the rotor. David |
Air Compressor Problem - Motor Stalls
David Inscribed thus:
wrote in message ... On Thu, 04 Mar 2010 05:13:31 GMT, lid (Sparks Fergusson) wrote: After reading all the posts, several things stand out. The most significant: There is no excessive current draw when the motor stalls. By all the laws of physics, that is flat out impossible. There are two explanations (well, three, but I'm assuming you aren't making this up). The first is slippage at the belt, motor pulley, or rotor. Given the knowledge you have exhibited, I say that can't be the problem; it's pretty hard to miss the fact that the motor is spinning but the belt is slipping. That leads to only one conclusion: The actual voltage to the windings is dropping. Possible causes are a bad thernal overload protector, bad run capacitor (some motors hide the starting capacitor inside, while the run capacitor is in a cupola on the side), or a corroded terminal so only one of the paired windings is used. All of these possible causes result in a lot of heat generated at one small point EXCEPT the single winding and the bad run capacitor. The single winding explanation is unlikely because it would not deteriorate gradually. That leaves the bad run capacitor. PlainBill There is one more possible cause: Some or all of the windings on the rotor that are supposed to be shorted are open. An induction motor works because windings on the rotor are shorted to induce the field needed to turn the rotor. David Thats a possibility, I've seen open rotor bars on induction motors. Sometimes they arc at the break and leave burn marks. -- Best Regards: Baron. |
Air Compressor Problem - Motor Stalls
On Thu, 18 Mar 2010 15:58:38 -0500, "David"
wrote: wrote in message .. . On Thu, 04 Mar 2010 05:13:31 GMT, lid (Sparks Fergusson) wrote: After reading all the posts, several things stand out. The most significant: There is no excessive current draw when the motor stalls. By all the laws of physics, that is flat out impossible. There are two explanations (well, three, but I'm assuming you aren't making this up). The first is slippage at the belt, motor pulley, or rotor. Given the knowledge you have exhibited, I say that can't be the problem; it's pretty hard to miss the fact that the motor is spinning but the belt is slipping. That leads to only one conclusion: The actual voltage to the windings is dropping. Possible causes are a bad thernal overload protector, bad run capacitor (some motors hide the starting capacitor inside, while the run capacitor is in a cupola on the side), or a corroded terminal so only one of the paired windings is used. All of these possible causes result in a lot of heat generated at one small point EXCEPT the single winding and the bad run capacitor. The single winding explanation is unlikely because it would not deteriorate gradually. That leaves the bad run capacitor. PlainBill There is one more possible cause: Some or all of the windings on the rotor that are supposed to be shorted are open. An induction motor works because windings on the rotor are shorted to induce the field needed to turn the rotor. David I've never seen that, but it is definitely a possibility and would also explain the symtoms. PlainBill |
Air Compressor Problem - Motor Stalls
wrote in message ... On Thu, 18 Mar 2010 15:58:38 -0500, "David" wrote: wrote in message . .. On Thu, 04 Mar 2010 05:13:31 GMT, lid (Sparks Fergusson) wrote: After reading all the posts, several things stand out. The most significant: There is no excessive current draw when the motor stalls. By all the laws of physics, that is flat out impossible. There are two explanations (well, three, but I'm assuming you aren't making this up). The first is slippage at the belt, motor pulley, or rotor. Given the knowledge you have exhibited, I say that can't be the problem; it's pretty hard to miss the fact that the motor is spinning but the belt is slipping. That leads to only one conclusion: The actual voltage to the windings is dropping. Possible causes are a bad thernal overload protector, bad run capacitor (some motors hide the starting capacitor inside, while the run capacitor is in a cupola on the side), or a corroded terminal so only one of the paired windings is used. All of these possible causes result in a lot of heat generated at one small point EXCEPT the single winding and the bad run capacitor. The single winding explanation is unlikely because it would not deteriorate gradually. That leaves the bad run capacitor. PlainBill There is one more possible cause: Some or all of the windings on the rotor that are supposed to be shorted are open. An induction motor works because windings on the rotor are shorted to induce the field needed to turn the rotor. David I've never seen that, but it is definitely a possibility and would also explain the symtoms. PlainBill PlainBill: I once saw a fractional HP induction motor on a fan had problems starting in a certain position. After moving the rotor a bit, it would run. There was one open winding on the rotor. The open was visible on the side of the rotor and applying a significant amount of solder cured the problem. There can be a lot of current in these shorted turns on a loaded motor. David |
Air Compressor Problem - Motor Stalls
In article , wrote:
On Thu, 18 Mar 2010 15:58:38 -0500, "David" wrote: wrote in message . .. On Thu, 04 Mar 2010 05:13:31 GMT, lid (Sparks Fergusson) wrote: After reading all the posts, several things stand out. The most significant: There is no excessive current draw when the motor stalls. By all the laws of physics, that is flat out impossible. There are two explanations (well, three, but I'm assuming you aren't making this up). The first is slippage at the belt, motor pulley, or rotor. Given the knowledge you have exhibited, I say that can't be the problem; it's pretty hard to miss the fact that the motor is spinning but the belt is slipping. That leads to only one conclusion: The actual voltage to the windings is dropping. Possible causes are a bad thernal overload protector, bad run capacitor (some motors hide the starting capacitor inside, while the run capacitor is in a cupola on the side), or a corroded terminal so only one of the paired windings is used. All of these possible causes result in a lot of heat generated at one small point EXCEPT the single winding and the bad run capacitor. The single winding explanation is unlikely because it would not deteriorate gradually. That leaves the bad run capacitor. PlainBill There is one more possible cause: Some or all of the windings on the rotor that are supposed to be shorted are open. An induction motor works because windings on the rotor are shorted to induce the field needed to turn the rotor. David I've never seen that, but it is definitely a possibility and would also explain the symtoms. PlainBill With all the talk, I would have liked to hear the final answer to the story. Is the compressor working yet. Its been a long time. greg |
Air Compressor Problem - Motor Stalls
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Air Compressor Problem - Motor Stalls
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(Solved!) Air Compressor Problem - Motor Stalls
"Wild_Bill" wrote:
The main problem is that the motor is being overloaded. As mentioned already, induction motors don't get tired or exhibit lower power output with age. It's taken longer than I hoped, but I have finally put my air compressor motor back together and it's working again! To review, over time, the compressor had developed a problem of the motor stalling before it reached full pressure. Bearing in mind everyone's suggestions, I took the motor apart and found that the bearings looked good, there was no sign of rotor/stator contact, and the internal wiring and connections looked OK. The only obvious problem was somewhat burned contacts on the centrifugal switch. Unfortunately, as I was taking it apart, I broke the voltage selector switch, and that's what's taken me so long to get around to fixing. Finally, with some JB weld and spare circuit board material, I managed to glue the switch pieces back together. I then cleaned and reseated all the internal connectors. I measured all the windings for continuity or shorts (they looked good.) I installed a new start cap, lubricated, and reassembled the motor. It ran, but wouldn't start. After disassembling it again, and some careful bending of the centrifugal switch, it was starting and running smoothly. Then, the moment of truth, I put the pulley and belt back on and fired it up. As I carefully watched the pressure gauge, I kept adjusting the regulator upwards. I ran it up to 140psi, and there was no sign of stalling or even slowing down! Success! I then adjusted the regulator back down to 120psi and buttoned everything back up. So, thanks to one and all for your help and suggestions. I'm back in business! |
(Solved!) Air Compressor Problem - Motor Stalls
It ran, but wouldn't start.
Am I missing something? |
(Solved!) Air Compressor Problem - Motor Stalls
William Sommerwerck wrote:
It ran, but wouldn't start. Am I missing something? Yeah, you can yank the pulley to get the motor turning, then it runs. But it won't start turning on it's own. Jeff -- “Egotism is the anesthetic that dulls the pain of stupidity.” Frank Leahy, Head coach, Notre Dame 1941-1954 http://www.stay-connect.com |
Air Compressor Problem - Motor Stalls
On Wednesday, March 3, 2010 at 9:13:31 PM UTC-8, Sparks Fergusson wrote:
I'm having a problem with my 20 gallon, single stage electric air compressor. It's acting like the motor is underpowered - it pumps up to about 95 psi ok, but then the motor stalls. The unloader bleeds the pressure off, the motor restarts, runs for a couple of seconds, and then stops again...repeat...repeat... It worked fine for years (The pressure switch would shut it down at about 120 psi) but over the past few months, it's gotten worse and worse, and now will only make about 90-95 psi before the motor stalls. I cleaned and lubricated the compressor itself, and it spins freely and doesn't appear to be binding or otherwise have excessive friction. The check valve/unloader is working and the piping is all open and clear. It seems like the electric motor (1/3 hp) just no longer has the oomph it used to. It starts up fine, no humming, no smoking, no bad smells, no clunks. It just doesn't seem to have enough running torque to handle the load like it did before. Anyone have any ideas? Thanks! Just replaced a "run capacitor on my 5 H.P. Champion compressor that was having a similar issue...All is well now. |
Air Compressor Problem - Motor Stalls
On Wednesday, October 21, 2015 at 4:52:53 PM UTC-4, wrote:
Just replaced a "run capacitor on my 5 H.P. Champion compressor that was having a similar issue...All is well now. Yes! This will very most likely be the problem. The motor is an AC induction motor, no brushes. But the run capacitor is critical to proper torque. And, if you are already in there and the happens to be a start-cap, do that one too. Peter Wieck Melrose Park, PA |
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