Compressor advice needed, please...

[ImpManiac]

Evening all.

I am refurbishing an air compressor I bought - distinctly secondhand - for £50 in January 2010. It was very, very dirty and dusty and didn't work. I was told it would need a "head gasket" to get it running again. But £50 for a 3HP, 150-litre air compressor... (It's an ABAC 3914-150.) Well, it'd be rude to pass on that!

Anyway, it turned out that the motor doesn't do anything more than buzz. The unit turns over by hand without difficulty, so I suspect motor or wiring issues.

I have the unit stripped down and have dismantled everything. I have cleaned everything carefully and propose to strip and repaint the air receiver.

I tried the motor again before I dismantled everything. I fitted a new starter capacitor. Still it just buzzed. I was going to dismantle the motor and needed to remove the pulley. I had the 3-leg puller on it and was tightening it, nice and square. The wretched pulley broke!

So, any ideas what could be amiss with my motor? It is a 240-volt, 3HP, 2.2 kW unit. Here is the rating plate.

Am I likely to be able to obtain a replacement pulley? I shall cut the remnants of the old one off, once I have measured the effective diameter.

If I need to get a replacement motor, does any of you know a good place? Can I get mine refurbed cheaper? What might be wrong with it?

Also, can anyone explain the wiring? I'd like to try it on the bench but am not going to take silly risks.

Any constructive advice you can give will be appreciated. Thank you in anticipation!

Paul

 

[the snooper]

sounds like the capacitor has gone on the motor

but as ive just read the rest of the post you have replaced it so it cant be that then did you replace like for like and was it new if it was second hand was it tested

 

[ImpManiac]

...did you replace like for like and was it new if it was second hand was it tested

Indeed I did. 50 microfarad, 400-450 volt, brand new, supplied by ABAC, who manufactured the compressor. I bought one when I ordered the gasket set.

Paul

 

[mike 109444]

Did you try the motor with no load ( remove the belt drive). If still same try whilst applying power, flicking the pully (unless it's to broken!) If motor runs then you have a problem with the "starting winding" if motor has one. Or might be tight bearings if it has not been run for a log time. Also MM do sell pulleys, mah have your size in stock sir. : )

 

[shenion]

There may be a start centrifugal switch in the motor. That turns the start winding/cap on off. May need contacts cleaned or may be stuck.

 

[ImpManiac]

Thank you, guys. I'll have a look.

Paul

 

[rtbcomp]

I did the same with an aluminium pulley. The trick is to get it hot before removing or fitting. If the motor is very old it may have an imperial shaft rather than metric.

I bought my motor from a guy on Ebay, can't recall the name, but he specialises in motors. There a a few on there doing the same, make sure you get one with copper windings.

 

[eil]

Check that you have continuity through both windings at the terminal block.

 

[ImpManiac]

Thank you, chaps! I shall take a look inside the motor in the next few days. I'll try to get some photos.

Paul

 

[eddie49]

As mike 109444 suggested, an induction motor without a start winding, or with a defective winding/capacitor/centrifugal switch, will still work, as long as the run winding is OK. Before cap start was common, this was known as "pulling on the belt". With no load, spin the shaft by hand and apply mains power, or apply power and, whilst it's sitting there buzzing, give it a spin.

 

[ImpManiac]

^^ Thank you. I shall wire the motor up and give that a try. It won't be for a few days, though, I suspect. But I shall come back with my observations.

Paul