strange motor single phase

[revjames]

asked to take a look at a table saw. Kity 0618 which is French. Owner was using it quite happily and his son turned it off using rotary insulator rather than off button. Saw wouldn't start after that. no power out of rotary switch. not the problem. Contactor burnt contacts. replaced contractor. not the problem. took old one to bits and repaired and put back. Still no good. Replaced Capacitor and still nothing. On pressing the start button MCB to bench power immediately trips. Motor start winding approx 7 ohm. Run winding 0.02 ohm. but why? all he did was turn off at isolator?

 

[Tony S]

Are you sure contact 3 is making?

 

[revjames]

Are you sure contact 3 is making?

tried it with new contactor as well as the original (after repairing it) 

 

[revjames]

OK, beginning to think the 2 black wires on the diagram are perhaps some kind of over temperature protection - thermistor type thing in the motor and the start and run wndings are configured on U1 V1 W1 terminals with the capacitor across the start winding. Need to get back to the workshop. Don't you just love answering your own questions?

 

[Geoff1946]

I was puzzled by the black wires too; they appear to be in series with  the contactor coil, BUT there is nothing there which would trip the circuit breaker.

It's hard to reconcile the other parts of that diagram. They don't seem to correspond at all.

 

[revjames]

Hmmmmm. got to the bottom of it today and you can have a laugh. Last week there was a problem with the DB in our workshop. Water had got in during a storm and cracks in the wall etc meant driving wind and rain had forced water in and as a result main 100a supply in sub tripped. Several MCBs needed changing out. I never gave it a thought. But it kept tripping every time I tried to start the saw. Today I realised the black wies are some kind of thermal overload so just connected the motor blue and brown to supply. Tripped straight away. I went to re set the MCB and it had been replaced with a 6a instead of a 32a so no wonder it kept tripping. Saw has now been rewired to the drawing and put back together and all is well!

 

[Sharpend]

Hmmmmm. got to the bottom of it today and you can have a laugh. Last week there was a problem with the DB in our workshop. Water had got in during a storm and cracks in the wall etc meant driving wind and rain had forced water in and as a result main 100a supply in sub tripped. Several MCBs needed changing out. I never gave it a thought. But it kept tripping every time I tried to start the saw. Today I realised the black wies are some kind of thermal overload so just connected the motor blue and brown to supply. Tripped straight away. I went to re set the MCB and it had been replaced with a 6a instead of a 32a so no wonder it kept tripping. Saw has now been rewired to the drawing and put back together and all is well!

next time save yourself the grief and call a spark!!

 

[roys]

Bet you started banging your head off the wall when you saw the 6A MCB

 

[revjames]

Bet you started banging your head off the wall when you saw the 6A MCB

It was a relief to finally get to the bottom of what was a very strange 'fault' ah well. It happens I suppose.

 

[Andy™]

I went to re set the MCB and it had been replaced with a 6a instead of a 32a so no wonder it kept tripping. Saw has now been rewired to the drawing and put back together and all is well!

:slap

 

[Sharpend]

:slap

Now you know it’s rude to laugh at another mans pain never mind a sparks pain!!