RESISTIVE LOAD BANK

[powerelectricman]

Hi all,

we want to load test a generator to confirm the operation of the generator voltage governor and the excitation circuit. is a resistive load bank is enough or an inductive load bank is required for this purpose?
thanks

 

[Reg87]

Resistive is fine. The only time I would use inductive load banks would be on powerplants.

 

[TheBlacksmith]

If there are large inductive loads that require significant reactive power be developed you may want to look at an inductibe bank or alternatively load the generator to near its KVA rating with the resisy=tive bank to ensure the voltage regulator and exciter can support nameplate amps.

 

[powerelectricman]

thanks for your input.
my question is when you use a resitive load bank, how is the Vf voltage and If current (field voltage and current) vary from no load state to full load state. I would imagine the field voltage and field current from AVR would be the same from the no load to full load states since it is a resistive load. what do you think?

thanks

 

[Skogsgurra]

No, not constant at all. The excitation has to make up for resistive and inductive voltage drop in the generator windings. There is also magnetic influence of the load current on the air gap flux, which needs to be compensated for by increased excitation current (and, of course, voltage).

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[waross]

The excitation voltage and current may approximately double from no load to full load on a diesel generator.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[catserveng]

Depends on your application and expected use. If this is a single island mode operating unit, like a standby, and your loads are well within the rated power factor of the generator, then a resistive test will likely be fine.

However, do you need to qualify droop or line drop compensation? Or does the end user or AHJ require testing that deomstrates not only full load real power but also full kVA load from the tail end? If so then likely a resistive/reactive load test will be required.

The last few years I worked for a CAT dealer, about 25% of the standby generator set sales/startup jobs required a full load test at nameplate power factor to satisfy end user or contract requirements. Saw this increasing over the years.

On shipboard diesel electric system units we always did a resitive/reactive load bank test as required by the marine regulatory agencies and to make sure the controls and protections operated as expected.

So my best answer is, "depends". More details on your unit, application and if you have any regulatory or contractural requirments can get you a more definate answer.

Hope that helps.

Mike L.

 

[powerelectricman]

thanks for the replies.
there is no requirement for kva testing. the single unit generator is used as an emergency power source and as soft load transfer during scheduled maintenance.
i wanted to confirm that the operation of speed and voltage regulation controllers with resistive load bank.

thank you