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.

 

[che12345]

Mr. Bill 6182 (Industrial)(OP)1 Jun 23 03:58
" #1. 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....#2. I measure the voltage on line 1 to line 2 @ 260V. Line 1 to line 3 @ 245V and line 2 to line 3 @ 251....#3. 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".
1. What is that a 3-phase converter. Is it a VFD?
a) The motor is not turning when directly connected to the lines?, or
b) The motor is not turning when connected to the output of the VFD?
2. Are the voltage measured (cross lines) are before or after the VFD? In any case, the variation is bigger than expected.
3. Are the voltage measured (across line to ground) are before or after the VFD? In any case the variation is not right. The voltage should be 1.732 lower than the line to line. Note: Line 2 to ground (225V) is far too high.
I think the source transformer secondary Neutral/Ground is NOT properly grounded, NOT connected, High resistance to ground etc..... Look into this as the first priority.
Che Kuan Yau (Singapore)

 

[LittleInch]

Also what is the frequency if you're going through a VFD?

Any current measurements when you turn the power on?

More details about the convertor needed.

Also can you post a picture of the diagram on the motor please.

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

 

[7anoter4]

In my opinion, if the three-phase induction motor does not start it is due lack of one phase-there are only two phases live.
At the measurement point, line-to-line voltages are all, more or less, 260 V and the angle between phase phasors are 60o- more or less. The phase-to-zero voltages are unbalanced, that means between this grounding point and the phases' star point it is a voltage drop of about 75 V due to a current leakage to ground. However, it is not connected with phase disappearance.

 

[Bill 6182]

che12345. As I typed the term 3 phase converter I didn't think it was the right term but I didn't know the correct one. I takes the single phase and manufactures a 3rd leg. I don't know if that is a VFD or not. It doesn't change the frequency. It looks like an electric motor and it spins when you turn it on. I think it is called a phase converter. The motor is not turning when directly connected to the magnetic switch that comes after the phase converter. 2 of the lines go directly from the breaker to the magnetic switch and the 3 line comes from the phase converter. All of the voltages are measured at the magnetic switch.

 

[Bill 6182]

I am trying to upload pics of the ID plates on the motor and the phase converter. I've not used this forum before. I must be doing something wrong.

 

[Bill 6182]

I guess it went through. Here is the converter.

 

[Bill 6182]

More on the converter

 

[Bill 6182]

This was inside the box of the converter

 

[waross]

Does the motor spin free when turned by hand?
Look for an open connection or blown fuses.
The motor may be faulty.
Those voltages are consistent with a rotary phase converter.
Don't start the phase converter and the motor together, start the phase converter and then start the motor.

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

 

[Bill 6182]

The motor does spinning free. It has a little drag but it is not locked up. I just put an new bearing in it. I always start the converter before the motor. LOL on the ohm's law thing.

 

[che12345]

Mr. Bill 6182 (Industrial)(OP)1 Jun 23 15:03
"....#1. As I typed the term 3 phase converter I didn't think it was the right term but I didn't know the correct one. I takes the single phase and manufactures a 3rd leg. I don't know if that is a VFD or not....#2. It doesn't change the frequency. It looks like an electric motor and it spins when you turn it on. I think it is called a phase converter. The motor is not turning when directly connected to the magnetic switch that comes after the phase converter. 2 of the lines go directly from the breaker to the magnetic switch and the 3 line comes from the phase converter. All of the voltages are measured at the magnetic switch"
.
1. Based on your description, it is a Rotary phase converter (RPC) not a VFD.
2. A RPC with single-phase input generates a three-phase balanced 120 degree apart voltage output, with no change in the frequency.
2.1 The measured L-L and L-G voltages are taken after the RPC seems not in order. It could be a faulty.
3. For a single-phase input to run a three-phase motor, the RPC shall be two x the three-phase kW rating.
4. In case the RPC is faulty, replace it with a standard three-phase VFD. Most standard three-phase VFD (heck, not ALL) allowed single-phase input and generates a three-phase balanced voltage output. Attention: the VFD shall be rated two times the three-phase motor (kW) rating.
Che Kuan Yau (Singapore)

 

[waross]

2.1 The measured L-L and L-G voltages are taken after the RPC seems not in order. It could be a faulty.

Close enough for the US and Canada.
The voltages to ground are similar to the expected voltages from a Wild leg delta or four wire delta system.
Unloaded, the capacitors may be distorting the voltages and phase angles.
Also, on iron core inductive circuits, hysteresis will distort the voltage wave form and cause noticeable errors with D'Arsonval meter movements.

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

 

[Bill 6182]

I check the resistance between each line at the motor. I have 0 ohms at all 3 tests. 140 A when I try to start it. I think not good.

 

[waross]

Does it smell "brown"?
It should be low Ohms, close to zero, but more than shorting the Ohmmeter leads together.
140 Amps is about right for a 10 HP motor on 230 Volts.
But on a rotary converter and with a shorted motor, that may be all that the rotary convertor can put out.


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

 

[waross]

Check winding resistances to ground.
Should be in the meg-Ohm range.

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

 

[Bill 6182]

Winding resistance to ground is mega. The tag on the motor says 34 A. I can't detect any resistance at all on the line. Maybe the tester is not that great.

 

[waross]

That is 34 Amps running at speed and under rated load.
Locked rotor starting current may be 5 or six times that.
eg: 170 Amps to 200 Amps.
But that is Direct On Line on a three phase grid.
The rotary converter may be limiting the current if the motor is shorted.
And, on AC the current is limited by impedance, a combination of inductive reactance and resistance.
240 Volts divided by 170 Amps or 200 Amps indicates 1.2 Ohms to 1.4 Ohms. The resistance is only a part of that and your multi-meter will show less than that on a healthy 10 HP motor connected for 230 Volts.
No, I didn't confuse 230 Volts and 240 Volts.
The standard supply voltage is 240 Volts.
The standard motor voltage is 230 Volts.
This is to allow for some voltage drop in the supply conductors.

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

 

[Bill 6182]

Thanks Waross. I understand alot of what you are saying but not all. I think you are saying that the motor my not be the problem. I should take it to a friends shop that has 3 phase power and try it there.

 

[Bill 6182]

So it purrs like a kitten at my friend's shop. It has 3 phase from the transformer. The voltages there are all 115 each line to ground. 220 between each lines. At my shop 1 of the lines has 225 to ground and 115 on the other 2. I just realized that I haven't checked the voltage at the motor in case there is a broken connection after the magnetic switch.