Motor autotransformer starting
Motor autotransformer starting
(OP)
I have complete installing a diesel generator that will start a 1500 hp 4160v motor useing a autotransfomer (two coil) . The Auto transfomere taps will be switched with 3 bypass contactors (close transition) using a a PLC.I will set the tap at 80% My question is the timeing on the contactors. For long do I leave the taps at 80% before opening the transition contactors and then the contactors to give me the 100%? thanks again





RE: Motor autotransformer starting
It depends on how long it takes the load to accelerate, my guess is you go to 100% once it reaches maximum revs at 80%. Another method might be to switch when the amperage falls back, I'm sure you have that available in a motor that size.
Regards
Roy
RE: Motor autotransformer starting
If you switch to full voltage at less than 90% full speed, you might as well use a full voltage starter.
You can detect when the slip is getting small by a significant drop in current.
Best regards,
Mark Empson
http://www.lmphotonics.com
RE: Motor autotransformer starting
JMarquez
RE: Motor autotransformer starting
The recommended method is to put one contactor at star point of transformer and hardwire the motor to the taps.
Sequence of Events
Close Star point Contactor
Close main contactor applying reduced voltage to motor.
Open Star point contactor (motor is now suppied thru transformer as a reactor.
Close 3rd contactor between Line and Taps thus shorting reactance.
I mmagine that you can close the shorting contactor as soon as the Star point opens (verify with N/C auxillary contact.
It's a while since I worked on one, perhaps someone else can add to this.
Roy
RE: Motor autotransformer starting
RE: Motor autotransformer starting
The "Kondorfer" starting method is indeed the correct
definition.It seems that the link from 2003[jacphi] is not available now.Never the less there are a lot of references on web.
On the attachment are 2 schemes -one of AEG one of ALSTOM.
But I did not find theoretical development yet.
Best Regards
RE: Motor autotransformer starting
Jmarquez
RE: Motor autotransformer starting
Just remember that while doing all this you DO NOT exceed the allowed motor start frequency.
Keith Cress
kcress - http://www.flaminsystems.com
RE: Motor autotransformer starting
As for the transition speed. Set a long time and start the motor. Monitor the current and/or the speed. When the motor quits accelerating or the current falls, dial back the timer until the transition occurs. If you can't adjust the timer, then time the start and set the timer to a little longer time than you found, say around 3-5 seconds.
RE: Motor autotransformer starting
I have always been told and understood that when playing with these transfer times with an Autotransformer you have to be aware of the Autotransformer Duty Rating. If the transition time is too long and you run through the Autotransformer longer than its Duty Rating, then you can damage the transformer. Starting frequency (starts/hr) applies to the transformer the same as it does the motor.
RE: Motor autotransformer starting
RE: Motor autotransformer starting
Regard
JMarquez
RE: Motor autotransformer starting