3 phase motor won't start 1

[Bill 6182]

I have a 10 hp motor and when I turn it on it just growls and won't turn. I have a 3 phase converter. I measure the voltage on line 1 to line 2 @ 260V. Line 1 to line 3 @ 245V and line 2 to line 3 @ 251. When I measure each line to ground I get line 1 @ 124, line 2 @ 225 and line 3 @ 124. The voltage stamped on the motor is 230-460. I have it wired for the low voltage diagram shown on the motor.

 

[waross]

The voltage to ground doesn't matter.
Look for an open circuit.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[jraef]

Where are you testing the RPC voltages? There should be a 3pole fused disconnect on the output of the RPC going to the motor, it sounds as if one of those fuses is blown so the motor is only getting single phase power.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[7anoter4]

I agree with warross. The power source is a delta connected secondary of a transformer and the grounding point is in the middle of a winding -as usual in most of cases. No leakage is expected. Sorry.

 

[LittleInch]

I still have no idea how these things work but this looks like the wiring diagram and more or less matches the picture of the internals.

Remember - More details = better answers
Also: If you get a response it's polite to respond to it.

 

[Bill 6182]

I think that diagram is accurate but has alot more details than I am familiar with. There are a bunch of capacitors with the RPC. I had to pause for about a week to get a cabinet job done but I will be back on it soon. I will check the circuit connection from the contactor to the motor. I will let you know. Much appriciated.

 

[waross]

That may be the wrong area to search.
That the idler motor is starting and running is a fair indication that this part of the circuit is working.
Look for problems with the contactor/starter that is not shown in this drawing.
You may have a loose connection or a bad contact in the part of the circuit not shown here.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[waross]

I still have no idea how these things work

When a single winding of a stationary induction motor is energized, force is generated internally but no torque is generated.
The rotor is more or less at electrical "Top Dead Center".
To develop torque and to start the motor spinning a second force must be added to act against the main torque and push the rotor off of "Top Dead Center".
That is done with a second winding, most often a start winding. (But there are exceptions.)
The second winding must be displaced both mechanically and by electrical phase.
In the Rotary Converter, one phase winding is energized directly and becomes the main winding.
The windings of the other two phases collectively become the start winding.
These windings are displaced mechanically and the capacitors provide the electrical displacement.
Once the rotary converter is spinning at speed, back EMF provides three phase power.
If the capacitors were disconnected when up to speed, the converter would work but at reduced capacity.
All of the power would have to be supplied by the main winding.
The capacitors provide some of the power to the second two windings resulting in increased capacity.
How much increased capacity? Proprietary information.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[edison123]

There you go. When a motor does not turn, that's always the first check.

Bad switch, blown fuse, broken or badly terminated cable lug, bad cable.

Muthu

http://www.edison.co.in