Part Winding issue

[SIPHON]

I currently have a CSH6563-40 bitzer Screw compressor that uses the part windings configuration to start up not sure as to why the start contactor /overload has failed. If the compressor is rated at 65 full rated amps what amp rating should the first contactor & overload be rated at? What amp rating should the second contactor and overload be rated at the timer is set 0.2 sec to interlock the run contactor ?

The current overloads are Schneider LRD33 and Contactors are LCI50D have the correct switching gear been selected ? :confused:

[goshen]

Hi
are you sure its a part winding start, and not a two contactor wye delta starter?
if it is indeed part winding what is the ratio?60-40 50-50??
this will determin the setting?
what kind of unit is this comp in?
good luck

[GHAZ]

Hi if the winding is p/wind then its 50% /50% so both contactors and overloads should be the same

[Grizzly]

Hi Siphon.
Goshen and Ghaz are spot on.
You first need to determine the start wind ratio.
As you state the contactors are the same size, I think it's safe to assume that you have a 50% 50%
Winding ratio.
With Bitzer for 50/50 your contactor needs to be rated at 60% Max Running Amps.
Whereas if it were a 60/40 part wind then the sizing is 70% and 50% max running amps.

I hope this further helps?
Grizzly

[SIPHON]

Hi
are you sure its a part winding start, and not a two contactor wye delta starter?
if it is indeed part winding what is the ratio?60-40 50-50??
this will determin the setting?
what kind of unit is this comp in?
good luck

I am a little confused in the 2 different configurations what is the difference in the two?

1. Part-windings
2. Start windings well was well explanined in my previous post http://www.refrigeration-engineer.com/forums/showthread.php?33447-Understanding-Three-phase-motors-with-multi-speed

[savoc]

i may be wrong but there should only 1 overload i think. the part winding contators pull in very quick .5> 1sec the current will be high but only for a sec. check the wiring diagram for a bizter

[Grizzly]

8269

Ok.
The bible according to Bitzer.
Or at least what I have found so far.
It may help?

Also follow this link and then select your relevant screw comp.
Then you can download the necessary manual, which will have definitions of the standard part wind setup.
http://www.bitzer.de/eng/products/docu/doc_det/12

Grizzly

[goshen]

Hi grizzly
nice posting !!!
best regards

[SIPHON]

Well illustrated and spot on info, just what i needed to make the troubleshooting easier

[D.D.KORANNE]

Each part winding to have a separate overload relay .
Olr to be set practically on the current drawn .
Contactor rating to be 70% of max current ....... For each of the part winding

[Grizzly]

Each part winding to have a separate overload relay .
Olr to be set practically on the current drawn .
Contactor rating to be 70% of max current ....... For each of the part winding

DD have you bothered to read any of the other posts?

Grizzly

[D.D.KORANNE]

We usually do the interlocking of part winding .... That is if first winding fails during operation of compressor the second winding is disconnected via control circuit to avoid the compressor to operateon only one 50 pc winding . This will shut down the comp

[GHAZ]

Hi ive never seen interlocking on p/wind because if one half goes the motor is no good and needs to be replaced any way, were as star delta are has a lock between star and delta contactor so the contactors don,t come in same time and blow

[goshen]

Hi ive never seen interlocking on p/wind because if one half goes the motor is no good and needs to be replaced any way, were as star delta are has a lock between star and delta contactor so the contactors don,t come in same time and blow
Hi
you may not of noticed a mechanical interlock ,but many old machines have a timer that prevents compressor from working if the two contactors of part winding dont engage ,the newer units have a digital input telling the controller if one stage didnt engage!
i personally try to convert all these part windings and star delta to a one stage start using a soft starter
good luck