Jon White Posted December 12, 2007 Share Posted December 12, 2007 Anyone know anything abotu AC motors? My 3HP compressor is sick! Its recently been blowing fuses on an increasingly regualr basis, but once started did run fine. However it now just blows the fuse all the time and will not start. It tries to start, turns over about twice, and then blows the fuse. My best guess is that the start up capacitor has died, and its just blowing the fuse casue of the inrush current, but I'm no expert when it comes to AC electrics. Anyone agree or otherwise? Cheers Jon Quote Link to comment Share on other sites More sharing options...
Gazzar Posted December 12, 2007 Share Posted December 12, 2007 That'd be my first guess, after checking all electrical gubbins for a build up of dust/loose connections/spiders webs etc. Isolate from mains first, obvious I know, but I forgot once! Also check the oil, as contaminated oil could increase the drag. Check drain plug, air filter and all the usual. If it is belt driven then take off the belt and try again - maybe a valve stuck in the pump etc. If it is an integrated pump motor then disconnect the air output and see if it goes ok. Did it restart fine? I mean, once the receiver had filled and been used a bit did the motor just cut back in? 3hp?? How was it wired? 110v or 220/240v? It wasn't through a 3 pin plug. was it? My thinking (I flatter myself) is that if it was on a 13 amp fuse + 240 ac mains and had been fine up until now, you were doing well, as a 3 hp motor can pull a lot of amps. Now, coming up to Christmas the power companies have trouble meeting demand and sometimes drop the voltage to 190 or so, which If I recall correctly, means for a given horsepower (watts) the amps would increase, pop goes the fuse. Of course I could be talking nonsense. Let us know how you get on - if unsuccessful then let us know more about the compressor - is it belt driven, seperate starter. These things are simple enough if you brake them down. If you are dismantling anything do take a picture of the wiring. I once had a compresser in I couldn't get to run well. Couldn't figure it - stripped everything rebuilt and the damb thing still wouldn't make 20 psi. Previous idiot working on it wired the motor the wrong way and it was running in reverse! Best of luck G. Quote Link to comment Share on other sites More sharing options...
Jon White Posted December 12, 2007 Author Share Posted December 12, 2007 Cheers for the tips. Its a SIP stratus 400/100. V twin direct driven. 3Hp = 2.2kW so should be well within the realms of a 13amp fuse! It is 240v single phase and runs via a 13 amp plug. I replaced the mains plug after it melted a while back which was due to corrosion. I also rebuilt the compressor end not long ago and refilled it to the correct oil level. Unfortunately the previous owner left it out in the rain, so its all got a bit corroded. I think I'll have a looksee inside the wiring box tonight and test the capacitor with a capacitance meter and go from there. I might also check that its all free to turn aswell I suppose! Cheers Jon Quote Link to comment Share on other sites More sharing options...
MogLite Posted December 12, 2007 Share Posted December 12, 2007 ....Unfortunately the previous owner left it out in the rain, so its all got a bit corroded Hey I resemble that remark Quote Link to comment Share on other sites More sharing options...
Hybrid_From_Hell Posted December 12, 2007 Share Posted December 12, 2007 Andy, You also forgot to mention "Warranty Expired" Nige Quote Link to comment Share on other sites More sharing options...
alfredenewman Posted December 12, 2007 Share Posted December 12, 2007 is the danfoss switch dumping the air when in the pump and out pipe when it cuts ehpower when the tank is full you should hear a hiss after it turns off other wise the motor will be trying to start a nearly locked pump result fuse blow try bleeding all air out of tank before you start up Quote Link to comment Share on other sites More sharing options...
Stevie D Posted December 12, 2007 Share Posted December 12, 2007 Mine did that a year or so back - most of the single phase 3hp motors have starting circuit / twin windings to get it spining up with a sort of centrifugal switch to change over to the main windings - my start winding was goosed - just blew fuses / trip every time it tried to start. Investigated a rewind - but cheaper in the ned to buy a new motor of ebay or from machine mart if in a hurry. Get somebody with a megger to test the resitance to ground through both sets of windings. HTH Steve Quote Link to comment Share on other sites More sharing options...
Jon White Posted December 13, 2007 Author Share Posted December 13, 2007 Right - checked the pressure gauge and it is only showing 50PSi so its not the pressure switch. Turns over nice and freely by hand. I took the capacitor off and tested it with a capacitance meter and its showing dead short, so I suspect there's the culprit. I'll stick a new one on it and try again. Cheers Jon Quote Link to comment Share on other sites More sharing options...
Jon White Posted December 13, 2007 Author Share Posted December 13, 2007 Hey I resemble that remark Quote Link to comment Share on other sites More sharing options...
Jon White Posted December 13, 2007 Author Share Posted December 13, 2007 Mine did that a year or so back - most of the single phase 3hp motors have starting circuit / twin windings to get it spining up with a sort of centrifugal switch to change over to the main windings - my start winding was goosed - just blew fuses / trip every time it tried to start. Investigated a rewind - but cheaper in the ned to buy a new motor of ebay or from machine mart if in a hurry.Get somebody with a megger to test the resitance to ground through both sets of windings. HTH Steve Well the capacitor didnt work! Looking like one of the coils is goosed then as you suggest............sigh.......... I need to persuade it all apart and I'll go from there. Cheers Jon Quote Link to comment Share on other sites More sharing options...
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