Dead Testing - 3Phase Motor and S-Plan

[whazza22]

When testing Insulation Resistance or Continutiy on a 3phase Motor, do you need to disconnect the cables from the motor?

Or do you just test I.R to the starter, then I.R from starter to motor? (as the starter will be open when dead)

Would a motor come under "equipment vulnerable to testing" section on test sheet?

Also, when testing S-Plan system, do you test the I.R to the fused spur on 500v, then test each component at 250v? - How would you test continuity of S-Plan?


Help much appreciated

 

[keith915]

Personally I'd always have the cable to motor disconnected to do IR test; and rightly or wrongly only test up to the fused spur on central heating systems when doing a PIR. Initial verification I'd always carry out 500V IR on heating systems before terminating.

 

[whazza22]

Is that incase it messes up starter?

Can a 3phase motor be tested on 500v?

What about testing all central heating components on 250v only?

 

[pmac10]

your testing the motor windings so alway disconnect leads and any jumper bars, cant help with your s plan question though mate

(more info) i test at 1000v on a 400v supply but 500v is perfectly acceptable, for 1000v test you should read>1.4Mohm but will probably read off scale,>1Mohm

 

[whazza22]

Could I not leave the cables in and test at 500v?

Would I need to test each phase on 1000v as its three phase?

 

[ringer]

for central heating:
500V from CU to fused spur.
250V from fused spur to boiler (there are unknown quantity of electronics in most boilers)

 

[whazza22]

Thanks, and would I do it on 250v for the other parts like the valves, stats and controllers?

 

[ringer]

controllers definitely have electronics inside. Some valves do too. So keep it simple - 500v before the fuse, 250v after.

 

[dichroic]

Insulation resistance tests should be made on electrically isolated circuits with any electronic equipment which might be damaged by the test voltage disconnected.

If you cannot disconnect it you should connect line and neutral together and then test between your line and neutral and your cpc. You do not start just testing up to a fused spur and ignoring the rest of the circuit and you do not test at 250v instead of the required 500v dc test.

When testing a 3 phase motor you leave the motor connected to its supply cables and you disconnect from the overload in the starter. That way you include the supply cables as well as the motor itself. Again test at 500v dc NOT at 1000v.

Regards

Dichroic

 

[whazza22]

Where do you you connect the line and neutral together? (not sure what you mean)

So, for a motor you disconnect both sides of the starter and connect them in connector blocks, then test?

 

[pmac10]

Insulation resistance tests should be made on electrically isolated circuits with any electronic equipment which might be damaged by the test voltage disconnected.

If you cannot disconnect it you should connect line and neutral together and then test between your line and neutral and your cpc. You do not start just testing up to a fused spur and ignoring the rest of the circuit and you do not test at 250v instead of the required 500v dc test.

When testing a 3 phase motor you leave the motor connected to its supply cables and you disconnect from the overload in the starter. That way you include the supply cables as well as the motor itself. Again test at 500v dc NOT at 1000v.

Regards

Dichroic

the op was asking about testing a 3ph motor, not a 3 phase motor and cables to a 3ph motor, and by all means set to 1000V as its a more thorough test

 

[dichroic]

the op was asking about testing a 3ph motor, not a 3 phase motor and cables to a 3ph motor, and by all means set to 1000V as its a more thorough test

Sorry PMAC silly me!! Lets test the motor and hope the supply cable is fine. What was i thinking ??

Oh and lets test the motor at 1000v dc and give it a thorough rogering on its laminations before we start it up

Dichroic

 

[pmac10]

does supply current and FLA mean anything to you
what if the motors a long distance fom the starter? where do you begin to fault find?
excess current damages windings in a ac motor, not dc voltage,

im thinking were talking different environments here, i test motors on an factory sight when i suspect a motor fault not routine testing, these motors may also be marked 415/660V and are delta connected, ill agree to disagree, but i work on the advice of a rewind specialist whom i send my faulty motors to