Harrison M300 The rebuild

[Tractor Man]

Sounds like a run capacitor is on its way out in the RPC. Does the RPC start ok? Have you checked the phase to phase voltages coming out of the RPC - if one of the run capacitors is failing one of the phases might have little or no voltage. If the motor is running on 2 phases that would account for the tripping and heat buid up.

Hope this helps!

 

[Shox Dr]

All the caps are new

How do I check the phase to phase voltage?

 

[brightspark]

All the caps are new

How do I check the phase to phase voltage?

run the machine and put a voltmeter across each phase should be 415 volts .any less on any phase and theres a problem a cheap mulimeter would do it

 

[Shox Dr]

L1-L2 425v
L1-L3 411v
L2-L3 411v

 

[brightspark]

L1-L2 425v
L1-L3 411v
L2-L3 411v

the motor conections are set for 415 v and not 240v if its a dual voltage motor i presume

 

[Tractor Man]

Those voltages seem fine for an RPC - high on L1 to L2 and a bit lower on the others.

Have you checked the relays/contactors in the rpc to make sure they're operating correctly? Also make sure all the wires are screwed correctly into the terminals - could be a loose connection???

Just another thought - there should be a relay or timer that cuts out the start capacitor after the rpc initially starts up. This could be sticking and leaving the start capacitor engaged which may cause the motor to heat up a stall.

 

[Shox Dr]

Timer works and cuts the start cap. It runs for ever with no load, nice and quiet, as soon as you turn the lathe on it vibrates. Should I see what the voltages are across the phases when under load


BS The motor hasn't been touched, and it worked fine before I stripped it

 

[brightspark]

Timer works and cuts the start cap. It runs for ever with no load, nice and quiet, as soon as you turn the lathe on it vibrates. Should I see what the voltages are across the phases when under load


BS The motor hasn't been touched, and it worked fine before I stripped it

yes check voltage under load each phase

 

[ford34/2]

Help

Sadly I cant be of much help, but I wondered what the 415 supply was-- Mains Or inverter/converter??

Stan

 

[Shox Dr]

Unload load

L1-L2 290v
L1-L3 390v
L2-L3 346v


The Start relay contactor closes as well

 

[brightspark]

Unload load

L1-L2 290v
L1-L3 390v
L2-L3 346v


The Start relay contactor closes as well

dont know the answer but thats quite low

 

[Tractor Man]

That is low!!! L1 to L2 theoretically should have the highest value as that is usually the single phase input just bumped up to 415v.

This makes me question the input wiring into the rpc. Have you checked that full 240v is getting in? Is it being run off a long extension of small diameter cable?

Ideally the rpc should be powered from a thick guage cable close to the main single phase distribution board otherwise any voltage drop is amplified massively in the output of the converter.

What hp rating is the rpc and what hp is the lathe motor?

 

[Shox Dr]

RPC is 3' below the main Board. Supply is 10mm. 7.5hp RPC lathe is 3hp.

Not checked input into RPC. I did have to mess with the wiring when I replaced the caps, so might have cocked up there

 

[Tractor Man]

It does sound like it is something to do with the caps with the load voltages being so low and the input cable easily up to the job - could be when you changed them they were accidently wired back in series not parallel.

In series the overal value decreases in parallel it increases the more caps you add.

Here's the maths:

Series: 1/C = 1/C1 + 1/C2...

Parallel: C = C1 + C2...

So in series the load voltage would be far less than it should be if the caps were in parallel...

 

[Shox Dr]

I'll have a look in the morning. Bedsville for me now.

Cheers

 

[hareng]

Control panel like this?

 

[tigler]

From what I've read so far it sounds like a phase imbalance. If it worked ok originally it is most likely a wiring error and the caps would be the most likely culprit as they determine the balance on the phases.

 

[Shox Dr]

Just got back from taking the MIL to the train station. Cuppa, toast and I'm on it


I've had a look at the caps, two are wired into one contactor, the other into another. On the other side they are all wired to one terminal on the coil

 

[Tractor Man]

Probably a stupid question but I assume that the caps were replaced with ones with exactly the same rating????

Also do you have any other 3 phase machinery of a similar rating to the lathe that you could run off the rpc to rule out any fault with the lathe?

Could you post a picture of the insides of the rpc? - might help the fault finding process!

 

[Shox Dr]

Pic's of inside RPC. The caps were purchased from Transwave, they are not the same value but was told they would be OK. I can get the values of the old ones as I still have them