compressor motor help - 3hp single phase

[stef1]

Hi guys,

Looking for a bit of advice on my hydrovane compressor motor. Its an old 1985 3hp single phase motor. I have just stripped it down to replace bearings and rewired the terminal box due to it being very old and most of the insulation had fallen off the cores leaving loads of bare copper.

Anyway, here is some pics for a start.







Now when i stripped it down, one of the first things I come across was the mechanical centrifugal switch, but I dont have a clue how or if it works? there is a mechanical part on the commutator which seems to function fine - it appears like it would throw out easy enough as speed. but there is no electrical switch or any other parts near it? so how does it work?

secondly, can anyone explain what terminals are what? I know the pic isn't to clear but I cant work it out. I have no idea what type or size the capacitors are bolted to the outside as they have been painted over but they do appear to be similar in colour to those inside the terminal box.


I have fired the motor up as it stands just now and it does appear to run as it did before - just without the bearing rattle. I have only replaced parts like for like so any problems or parts missing have been like that for a while. I have put quite a few hours on this motor so far.
Cheers in advance
stef

 

[the snooper]

the centrifugal switch disconnects the start caps once the motor is running fast enough also the run caps alter the phase of some of the winding so that will account for some of your connections.
if I were you I would contact the Leroy somer web site and ask them for the specs on that motor including the value of all the capacitors for future reference

 

[stef1]

the centrifugal switch disconnects the start caps once the motor is running fast enough also the run caps alter the phase of some of the winding so that will account for some of your connections.
if I were you I would contact the Leroy somer web site and ask them for the specs on that motor including the value of all the capacitors for future reference

cheers for the reply.

I'm confused by the centrifugal switch though as it has a mechanical part but no electrical part. so when it spins up and is forced out, i cant see that it would affect anything

 

[the snooper]

there has to be a switch somewhere , you must have missed it, don't suppose you have a pic of it ?

 

[the snooper]

the switch would be in the main body of the motor not on the shaft that turns

 

[stef1]

I dont have a picture of the internals, definitely no electrical switch of sorts inside though. Just the mechanical part on the commutator. I'm wondering if someone has played about with this before.. I would have thought it would have burnt out if the coil wasnt disconnecting though..

I found a wiring diagram of sorts on the inside of the terminal box lid also. it doesnt explain much to me but it is all numbered.

 

[stef1]

2 pictures to follow shortly. Looking at it, I wonder if my motor has a thermistor in the start windings though..

 

[the snooper]

a thermistor is only a temperature sensitive resistor, the resistance changes as the heat increases or decreases so nothing to do with centrifugal switch

 

[stef1]

copied from wikipedia..

In capacitor-start designs, the second winding is disconnected once the motor is up to speed, usually either by a centrifugal switch acting on weights on the motor shaft or a thermistor which heats up and increases its resistance, reducing the current through the second winding to an insignificant level. The capacitor-run designs keep the second winding on when running, improving torque.

I just wondered if that was a likely answer as I cant see any switch.

Im going to measure across the capacitors when the motor starts up and is running to see if they do somehow disconnect

 

[the snooper]

if that's the case surely there is no point in having the centrifugal mechanism on the shaft it would only increase manufacture costs, remove the cover and have a look in the end of the motor switches can be located there

 

[stef1]

exactly what my thoughts. I am just uploading a couple of pics with the end cover off. Im also confused as to why one of the capacitors on the side (run capacitors) has 4 wires and the other has 2?

 

[stef1]

 

[the snooper]

Are those pic front or rear of motor

 

[stef1]

those are from the rear end of the motor.

 

[the snooper]

Well your wiki search looks to have answered your question then

 

[the snooper]

Your wiring diagrams show how to reverse the motor

 

[stef1]

Your wiring diagrams show how to reverse the motor

ahh right. ok thanks (I have just noticed the arrows...duhh lol)

I'm still trying to figure out what does what in the terminal box and I'm beginning to wonder if someone has added 3 of the capacitors for some reason?
the bottom capacitor bolted on the outside is connected to terminals 5 (live supply) and 6 (looks to me like the start winding)

 

[eil]

The run cap will be connected to the start winding and either Live or neutral, its called a run cap as it stays in circuit when the motor is running. The reason you would have two start caps and two run caps is to double the capacitance (when connected in parallel) making a start cap value of 180 - 230uf.

 

[stef1]

Thank you for the reply.

I was going to do some measurements and things inside the terminal box but I just wanted to get it back together and fitted to try out my new air filter/regulator and check for leaks..

I quickly done some current measurements with a clamp on meter. it appears everything is functioning quite well to me. And its lost its rattle from the bearings! overhaul complete I think

60A starting
5.5A no load
12.5A with load

 

[simplysimon]

it look like a switch start motor that someone has removed the switch and replaced with caps, maybe its had a motor swap at some time, I wouldn't have thought hydrovane would use cable ties to hold on something so important and be visible.