Alternator FAT without AVR 1

[jimmy2times]

should an alternator go through factory acceptance test (FAT) with its contract AVR, i.e. not use alternator manufacturers test bench AVR. These are fairly large diesel generator 4675kVA, 690V.

What are risks in not using the project designated AVR?

What additional tests should be considered when the two are finally combined on site for first time?

 

[catserveng]

Ideally testing controlling components with the equipment is the best way to go, however on a unit that sive the AVR is likely mounted in the switchgear, and is probably already in the hands of the switchgear vendor for installation.

Is the AVR used in the factory test the same type AVR? At a minimum during the factory tests assure you have the field amps and field volts for such test points as no load rated voltage, 25, 50, 75 and 100% load points, to use for comparison when the unit gets to site.

Is it an analog or digital regulator? The basic steps prior to onsite startup are to assure the voltage sensing leads are the correct phasing, the droop CT is wired for the correct polarity and in the correct phase, and that the voltage adjust interface to the AVR from whtever else controls it, like manual voltage adjust, synchronizer, and power factor or VAR controller, is properly installed.

At inital start, usually before allowing the AVR to turn on I check the residual voltage at the AVR terminals, just to make sure all three phases are reading as expected. Then turn on the AVR, the voltage should ramp and not overshoot. Then make sure you have proper voltage control, if you ask it to raise it should go up and if you ask it to drop it should go down, smoothly and at a consistant rate. Check the no load field volts and amps, compare to the readings you have from the factory test. Make initial stability adjustments. Then procedure with your checks for loading.

Are you operating parallel to grid or something else, or in an island mode of operation?

The most common startup problem I run into in usually the droop CT not wired correctly, usually the polarity at the AVR is incorrect but occasionally it ends up in the wrong phase. In an island mode of operation other than the droop not working as expected it doesn't cause much greif, however in a paralleling situation can cause all kinds of headaches.

In parallel applications the adjustment that is usually the hardest to get right, at least in my experience, is the stability, since whatever you're paralleled too also affects the voltage. The AVR manufacuturer should have guidelines for proper stability adjustments.

Hope that helps, Mike L.