Dorin Y3060CB stalling

[nike123]

I have problem with this compressor starting in flake ice machine.
When unloaded (intake and discharge valves open to atmosphere) it start perfectly, but when normally connected in system with refrigerant (R22) it wont start.
It is part winding start motor.
I checked voltage when one part of winding is at LRA and it is 370V (supply voltage is 390V before start and motor is rated at 380-420V / 3 / 50Hz)

LRA when one part of windings is energized is 110 A.
Declared LRA for full windings at 400V is 190A.
I suspect that is nothing wrong with power supply and that problem is with bearings or something else mechanical within compressor.

I will appreciate if someone could point me with its experience in compressor troubleshooting.

[Gary]

If voltage under load at the compressor terminals is less than supply voltage, then the current must be going through a resistance, such as burnt contacts in the starter.

[nike123]

If voltage under load at the compressor terminals is less than supply voltage, then the current must be going through a resistance, such as burnt contacts in the starter.


I did not noticed any difference between power supply terminals and compressor terminals.
Is it true that with part winding start motors compressor normally could even not start turning with only one part winding energized?
I don't have much field experience with part winding start.

[Gary]

I did not noticed any difference between power supply terminals and compressor terminals.


Are you saying that the voltage at the power supply terminals dropped to 370V when it tried to start?

[nike123]

Are you saying that the voltage at the power supply terminals dropped to 370V when it tried to start?
Yes!...............

[Gary]

Yes!...............

I'm fairly sure you didn't overload the power company and drop their voltage. So there must be some resistance in between. Perhaps the main breaker? If you track backwards you should find a point where trying to start that motor does not drop the voltage.

[Gary]

While you are tracking back, look for loose wiring connections, burnt contacts and hot spots. If you have an IR thermometer this might make finding the problem easier. Resistance = heat.

[nike123]

I'm fairly sure you didn't overload the power company and drop their voltage. So there must be some resistance in between. Perhaps the main breaker? If you track backwards you should find a point where trying to start that motor does not drop the voltage.

I will check as you suggested.
In regard of overloading power company, I could only say that, this is normal here, that voltage drops below 10% of nominal and nobody (i mean power company of which you bought power capacity for huge amount of money) is responsible for that. Especial when tourist season is here and number of occupants in our small towns are multiplied by factor 3-5.

[nike123]

While you are tracking back, look for loose wiring connections, burnt contacts and hot spots. If you have an IR thermometer this might make finding the problem easier. Resistance = heat.

Yes, I have it and I will check that.
Thanks Gary.

[D.D.KORANNE]

What is the percentage of part winding ?

If it is 60:40 , power wiring could be in error since the compressor runs without the load ( free running ) but when connected it does not . Does it humm when put on load ? Also the part winding should have the correct sequence of power supply.

Check the resistance of pw .
Sometimes the winding opens up its insulation considered to be a mfg defect .

[Yuri B.]

I am 100% sure there was a mechanical fault. Familiar strory - almost always after the comp was in reparation somewhere else - they claim they test it alright, but when you switch it to main at site it does what Nike has descibed.

[Gary]

Also check for undersized wiring as this can provide excessive resistance, too.

[nike123]

Sorry guys for not responding at yours questions for some time, but I was away from my comp last week.

Problem is solved by changing starting timer of second winding, which did not performed as it should (it did not energized second part winding contactor at all). After checking some literature and after this experience, I learned that some motors could not start turning without second part winding energized. Here, time difference for windings is 0,2-0,4 seconds.
Now, it purr like cat.
It draws 33A and voltage drop is only 10V.

[Yuri B.]

10 V drop just at nominal load is huge. (What at start - 40 V ?)

[Yuri B.]

Sorry, you had said it earlier - 20V.
But numbers are strange anyway.

[nike123]

Sorry, you had said it earlier - 20V.
But numbers are strange anyway.


Maybe because my voltmeter is not true RMS!

The way at which installations are made here, such voltage drop is not something which I consider significant and it is well within limit of +-5% of voltage variation.