Collie
13-12-2010, 08:10 PM
Hi lads, have a lovely problem for you to get stuck into! :D
CIAT air cooled water Chiller with 2 circuits. Each circuit has two stages so there are four compressors in the chiller all of equal capacity. I dont have chiller details as name plate is long gone at this stage.
Copeland Compressor
D8SK-600X-AWM
The fault is identical in each compressor.
I have 3 phase compressors which use Part-wound starting. The two motors turning the shaft split the load 60% and 40%. So in my terminal
box I have 6 terminals, the "larger" motor being supplied with 3 phases
and the "smaller" one also. The windings are in a star/star star
configuration.
They are set to run at 50hz, full load current 102 amps, 60kW, 1450rpm.
There is no Cos value given on the name plate though.
Mechanically they start and run fine but when running, the larger motor
pulls approximately 32-35 Amps which is fine, but the smaller motor
pulls 45 amps!!!. The MCB rating is 50 Amps and during the summer when
it was hot they were tripping regularly.
I've measured the voltages at 230 volts AC to earth and apporx 400
between phases. I've put a megger on the windings and thats ok too.
I've measured the resistances with my meter and found the smaller
winding equal at approximately 1.2 Ohms and the larger winding also
equal at 0.4 Ohms.
According to all my data, they should be running fine?? I've ruled out
incorrect wiring as ive belled out the cables and reconnected them as
per terminal box wiring diagram and still the same.
Originally I had found the oil in the compressors had turned acidic so
i changed it and thought this would resolve the problem by reducing
friction in the mechanics but it has not changed anything and im realy
at a loss as to where to go from here. I thought maybe the acidic oil had damaged the insulation on the windings but its passed the megger test a couple of times over. I've checked the oil regularly and its still fine now.
Not sure why the oil was acidic??......thats a whole other thread :off topic:
Any thoughts on this current issue guys??
Thanks
CIAT air cooled water Chiller with 2 circuits. Each circuit has two stages so there are four compressors in the chiller all of equal capacity. I dont have chiller details as name plate is long gone at this stage.
Copeland Compressor
D8SK-600X-AWM
The fault is identical in each compressor.
I have 3 phase compressors which use Part-wound starting. The two motors turning the shaft split the load 60% and 40%. So in my terminal
box I have 6 terminals, the "larger" motor being supplied with 3 phases
and the "smaller" one also. The windings are in a star/star star
configuration.
They are set to run at 50hz, full load current 102 amps, 60kW, 1450rpm.
There is no Cos value given on the name plate though.
Mechanically they start and run fine but when running, the larger motor
pulls approximately 32-35 Amps which is fine, but the smaller motor
pulls 45 amps!!!. The MCB rating is 50 Amps and during the summer when
it was hot they were tripping regularly.
I've measured the voltages at 230 volts AC to earth and apporx 400
between phases. I've put a megger on the windings and thats ok too.
I've measured the resistances with my meter and found the smaller
winding equal at approximately 1.2 Ohms and the larger winding also
equal at 0.4 Ohms.
According to all my data, they should be running fine?? I've ruled out
incorrect wiring as ive belled out the cables and reconnected them as
per terminal box wiring diagram and still the same.
Originally I had found the oil in the compressors had turned acidic so
i changed it and thought this would resolve the problem by reducing
friction in the mechanics but it has not changed anything and im realy
at a loss as to where to go from here. I thought maybe the acidic oil had damaged the insulation on the windings but its passed the megger test a couple of times over. I've checked the oil regularly and its still fine now.
Not sure why the oil was acidic??......thats a whole other thread :off topic:
Any thoughts on this current issue guys??
Thanks