Electrical/Electronic Engeering. Underfrequecy/undervoltage problem
Electrical/Electronic Engeering. Underfrequecy/undervoltage problem
(OP)
Pls. i need a professional advice on these issue.
I am currently handling a job in a site and they have a problem with their CAT 3516 NG Engine, The Gen. start up on idle and when taken to rated, after 1 min it shut down on Underfrequency/Undervoltage. pls what do i do to resulve this problem
I am currently handling a job in a site and they have a problem with their CAT 3516 NG Engine, The Gen. start up on idle and when taken to rated, after 1 min it shut down on Underfrequency/Undervoltage. pls what do i do to resulve this problem





RE: Electrical/Electronic Engeering. Underfrequecy/undervoltage problem
If you have an electrical problem with the set, and the voltage is not building up you will also get an Underfrequency/Undervoltage trip.
If the operators are starting at idle and then ramping up the speed, they may not be setting the speed properly.
Is there any interpersonal friction on the job? The operators may be messing with your head and purposely setting the speed wrong. Watch for grins and winks between the operators.
Bill
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"Why not the best?"
Jimmy Carter
RE: Electrical/Electronic Engeering. Underfrequecy/undervoltage problem
There are, depending on configuration and controller in use, almost hundreds of reasons on why you'd get an underfrequency / undervoltage, least of all the reasons that Waross alluded to. Is the set new? Has it been commissioned previously? Depending on controller, there are at least a couple of options I could think of to trick the unit, and thats without the possibility that its actually falling over.
Thanks to Waross for pointing out the operator possibility. I'm just thankful that no operator has ever done that to me.
RE: Electrical/Electronic Engeering. Underfrequecy/undervoltage problem
RE: Electrical/Electronic Engeering. Underfrequecy/undervoltage problem
RE: Electrical/Electronic Engeering. Underfrequecy/undervoltage problem
Bravo 3
RE: Electrical/Electronic Engeering. Underfrequecy/undervoltage problem
This is a small three phase alternator on the end of the main alternator shaft. It generates about 200 volts to power the AVR (automatic voltage regulator). Check your PMG fuses and wiring, and then check the PMG for failed windings.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Electrical/Electronic Engeering. Underfrequecy/undervoltage problem
With engine running at rated speed (this engine has both low and high speed ratings, 1200/1000 low speed for 60/50 hertz, and 1800/1500 high speed for 60/50 hertz) first check PM power to voltage regulator, terminals 26, 28, 30 in generator connection box and on voltage regulator (numbering same on both models), should be about 100 VAC at 240 Hertz for 60 hertz rating, can be as low as 80 and as high as 120 VAC. Check sensing on regulator, terminals 20, 22, and 24, standard CAT configuration was 240 VAC sensing, either center tapped or by using 2:1 PT's.
Check field output, nominal CAT exciter field runs about 10-12 VDC at rated speed no load voltage.
>Stop unit, remove F1 and F2, measure resistance, should be about 3.5 to 4 ohms.
If you are flashing the field with 12 VDC and not getting near nominal voltage, likely suspect is rotating recitifer and surge suppressor assembly. CAT had quite a few problems with that assembly, both diodes and surge suppresor, and service replacement is the entire rotating rectifier assembly. You should check with your CAT dealer to get correct replacement part number, as there where several part number changes over the last few years. There have also been a fair number of pilot exciter rotor failures in some of the frame sizes you'll likely see behind that engine.
Hope that helps