Single-phase generator with 1.0 Power Factor

[FaradayFF]

Hey guys,
For a single phase generator in the range of 22kW, with pf of 1.0, would we get 22kW only for purely resistive loads? The data sheet I'm looking at is confusing me, they are showing 22kVA and 27kVA for standby rating. Would we expect to get 27kVA out of this generator when it is powering inductive loads with 0.8pf?
Thank you,
EE

 

[topgone]

Hey guys,
For a single phase generator in the range of 22kW, with pf of 1.0, would we get 22kW only for purely resistive loads? The data sheet I'm looking at is confusing me, they are showing 22kVA and 27kVA for standby rating. Would we expect to get 27kVA out of this generator when it is powering inductive loads with 0.8pf?
Thank you,
EE

Don't confuse yourself with ratings. A 22 kVA generator rated as a standby unit will be capable of 27 kVA ran as prime unit with varying loads. The standby rating is 80% lower than the continuous rating of the generator.

 

[electrofelon]

Don't confuse yourself with ratings. A 22 kVA generator rated as a standby unit will be capable of 27 kVA ran as prime unit with varying loads. The standby rating is 80% lower than the continuous rating of the generator.

That's what I thought, but he did say "they are showing 22kVA and 27kVA for standby rating". I don't know exactly what that means, there's got to be some difference indicated about the two values. Perhaps a picture of the rating info would help.

 

[kingpb]

All generators (typically anyway) have a standard rated 0.8pf. This means that a rated 22KW machine @ 0.8pf, is rated 27.5KVA. That is regardless of back-up, prime, etc. That means you can provide 22KW of resistive load, and simultaneously provide 16.5KVar of reactive load. Those are the maximums. If you have a reactive capability curve for the gen, you can determine from it the min and max capabilities and values at different power factors. There are additional capabilities beyond the listed rating for different operating scenarios.

 

[PD1972]

... The standby rating is 80% lower than the continuous rating of the generator.

It's usually the other way around. The prime rating is less than the standby rating. It makes sense to me as standby gensets are used for intermittent backup versus a prime genset which would be used continuously as the main source of power.

I am going to guess the product data sheet you are looking at is for a generator that may be ordered in either single phase or three phase. That's why you see a generic 22kW/27.5kVA rating.

For a single phase configuration, it is probably going to be 22kW @ 1.0pf so 22kW/22kVA. It is not 22kW @ 0.8pf so you can't treat it as 22kW/27.5kVA. The 22kW/27.5kVA rating only applies to the three-phase configurations, which would have a 22kW @ 0.8pf rating.

Not sure what product data sheet you are looking at, but see the Generac product data sheet for a small diesel generator below and how it makes that distnction.

 

[FaradayFF]

It's usually the other way around. The prime rating is less than the standby rating. It makes sense to me as standby gensets are used for intermittent backup versus a prime genset which would be used continuously as the main source of power.

I am going to guess the product data sheet you are looking at is for a generator that may be ordered in either single phase or three phase. That's why you see a generic 22kW/27.5kVA rating.

For a single phase configuration, it is probably going to be 22kW @ 1.0pf so 22kW/22kVA. It is not 22kW @ 0.8pf so you can't treat it as 22kW/27.5kVA. The 22kW/27.5kVA rating only applies to the three-phase configurations, which would have a 22kW @ 0.8pf rating.

Not sure what product data sheet you are looking at, but see the Generac product data sheet for a small diesel generator below and how it makes that distnction.
View attachment 2574256

Thank you for providing a response. If a single-phase generator is supplying an inductive load, and is running at 0.8pf and up to its full capacity, would it not output 27.5kVA? Not all loads are resistive.

 

[PD1972]

Thank you for providing a response. If a single-phase generator is supplying an inductive load, and is running at 0.8pf and up to its full capacity, would it not output 27.5kVA? Not all loads are resistive.

If the manufacturer lists the unit at 22kW @ 1.0pf then the generator can be expected to have a max output of 22kVA. I do not know why the single phase units are at 1.0pf unlike the three phase units which are listed at 0.8pf, but I am assuming there is a reason for it.

 

[kingpb]

Single phase units are typically utilized to provide more resistive load, so they rate them at 1.0 pf. I'm sure a valid argument could be made against that, but it is what it is. So if you have a 22KW, 1.0pf, just means the maximum you can produce is 22KW/KVA, and if you have a non-resistive load, the maximum power output is going to be less; i.e. a .9 pf means you can only produce 19.8KW, etc.