Generator set KVAR loading calculation

[thakerrohit]

Would manufacturer's give total data to determine the kVAr capability and what are the chances that all calculations are valid in field. Specially when client has parallelled generator and loads bordering on the kVAR parameters. How necessary is it to test at site with kVAr loading?

 

[charlie b]

Re: Generator set KVAR loading calculation

I really do not understand what you are trying to ask.

The manufacturers give the ratings of their generators in terms of KW and power factor. You can calculate the rated KVAR from that information.

KVAR = (KW / PF) times sin [arccosine (PF)]

As to whether it is "necessary" to test, that is up to you.

 

[Leitmotif]

Re: Generator set KVAR loading calculation

Would manufacturer's give total data to determine the kVAr capability
REPLY Yes - on the nameplate or in the manual

and what are the chances that all calculations are valid in field.
REPLY The manufacturers ratings will not change for the alternator regardless of where installed (with exception of altitude - read the manual)

Specially when client has parallelled generator and loads bordering on the kVAR parameters. How necessary is it to test at site with kVAr loading?
REPLY If you are nearly full loading paralleled units you better know who has got how much of total load both KW load and KVAR load. IF they were mine I would have full set of instruments.

 

[coulter]

Re: Generator set KVAR loading calculation

thakerrohit -

Dan is absolutely right - get the data from the nameplate.

As for the calcs working in the field, generator manufacturers don't tend to lie about ratings on industrial generators. However, they do rate their generators at the most favorable ambient conditions. So, if your installation is limited on cooling, altitude, or has air intake restrictions or high ambient temperatures, then the gen likely will not make rated output.

A couple of questions:
1) How do you know the customer's load is bordering on the gen KVAR limits? Is this something measured on an existing installation? Or is this calculated for a new installation?

2) What test are you thinking of performing? Is this a new installation and you want to make sure the gens will output as specified? Are you considering getting a loadbank with a variable pf?

More information about the installation will likely get better answers.

Dan is right about the required instrumentation - you need it. I would be surprised if it is not there. Every paralleled gen installation I've seen has the needed instrumentation.


carl

 

[thakerrohit]

Re: Generator set KVAR loading calculation

Yes the installation is old one. The question about test is more with respect to how effective the paralleling scheme is. Some generators may not have good scheme and that may result in unbalanced kVAR loading. Yes the instrumentation is there and will help. Thanks to All.