diference on current ripple on excitation
diference on current ripple on excitation
(OP)
i have a problem with an excitation system, i have a short diode alarm, i know the ripple must be higher than normal, how much % of ripple i must have? and now we suppose we have a 6 pulses bridge on the avr, and if one of the SCR have the driver disconected, so it´s not working, how would change the current ripple? cause the voltage ripple have change, and how much the voltage ripple must change? could somebody help me with some literature....
thanks a lot
thanks a lot





RE: diference on current ripple on excitation
I would think that if you have an open diode on a rectifier, then ripple would go up.
But if you have a shorted diode, could be high currents circulating about to damage something else until some other component or fuse interrupts the circuit.... wouldn't it?
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(2B)+(2B)' ?
RE: diference on current ripple on excitation
The diode fail protection should sense the failed/shorted diode and trip the unit within about 10 seconds. This protection works by sensing the exciter field current, if it is abnormally high (over ceiling current) for more than the set delay time, a trip will occur. During normal regulation, and on start-up ceiling current may be reached for some seconds or fraction of a second.
If it is a full static exciter then:
Other means are used: Blown fuse detection (tripping flag on the bad fuse has operated), or current comparison circuit between sections of the bridge(s)has operated. In that case likely the unit is designed to operate with one failed diode at reduced rating.
rasevskii
RE: diference on current ripple on excitation
I have used this information to help develop settings on other manufacturers AVR's with similar functions with pretty good success.
www.basler.com
Hope that helps, Mike L.
RE: diference on current ripple on excitation
RE: diference on current ripple on excitation
Why are you concerned about ripple? Excitation systems are designed with reliability in mind, and all the necessary protection functions are included with any system from any reputable supplier.
It sounds like a theroretical exercise that you are in the midst of. The field supply of any generator or brushless exciter is not affected by ripple due the high inductance, all diode and thyristor rectifiers produce some degree of ripple but it doesn`t matter.
See above posts. Do not tinker with excitation equipment. Call in someone from the OEM or an expert. Do not change or disable the protection settings from the original commissioning, which was likely done by the OEM or his rep.
rasevskii
RE: diference on current ripple on excitation
After we reclaim manufacturer, he said they could feel on their control the diference between a ripple change on the voltage cause of the SCR open, and i wonder how much would be on % the change on the ripple of voltage, and % on change on the ripple of current.....
And how could i comparate it with the ripple on the current with a short diode or open diode.....
As you see is just to know a little more about it just to discuss with the manufacturer.
Thanks a lot for your ideas, maybe i must explain it better on first time.
RE: diference on current ripple on excitation
The ripple voltage will be significantly higher. It is a fairly trivial task to sketch out the waveforms - the generator field is a textbook 'highly inductive load' so you can find plenty of examples to start you off, but obviously you'll need to assume that one switch is open circuit.
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If we learn from our mistakes I'm getting a great education!
RE: diference on current ripple on excitation
thanks