KVAR Contactor.

I have a few ABB UA95-30 contactores and they have printed a power table in kvar, not in kw. Are they specialy made for condensers
aplications? Can i use the to build a delta wye motor starter? Finaly, is there a phisical diference betwen the contacts in a kvar contactor and a kw or hp contactor? Fon any help, thenks in advance. CLT
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http://library.abb.com/GLOBAL/SCOT/SCOT209.nsf/VerityDisplay/725FBA10F5471F66C1256F430042DAB9 /$File/1SFC101030D0201.pdf
When you read the literature for these contactors, it states:
"The UA..RA contactors are fitted with a special front mounted block, which ensures the serial insertion of 3 damping resistors into the circuit to limit the current peak on energization of the capacitor bank. Their connection also ensures capacitor precharging in order to limit the second current peak occurring upon making of the main poles."
Would I use these on a motor? As described in the acrobat file, no way.
The acrobat file does not show the mechanics of this contactor and how the damping resistors fit in.
I'm guessing that the damping resistors are put in series with the capacitor bank for a few seconds on initial closure, then once the capacitor bank is charged up the resistors are taken out of the circuit when the main poles on the contactor pull in.
But then when I read about the "precharging" part, that sounds like the resistors are in the circuit when the main poles on the contactor are open. If that's the case, then when the contactor is turned off then there would still be voltage applied to the motor via the damping resistors.
Using these contactors, as built, as a motor starter would either blow the resistors in the contactor or play havoc on the motor windings during start ups.
I don't know if the "special front mounted block" can be removed from the assembly to create a normal contactor. If so and if the contactor acts like a normal across the line contactor, and if I was really, really desperate, then I don't see why they couldn't be used to control a motor in an act of desperation.
Even if I did put one in, I would definitely get the right type of contactor ordered and installed ASAP. These contactors were probably UL tested for capacitor banks, not UL tested for motor control.
To figure out KVAR to KW if used as motor starters, you need to contact the motor manufacturer and find out the power factor for the motor. US motors hardly list this on the nameplate, but I've run into European motors that have either "pf" or "cos theta" on the nameplate.
The power factor is the cosine of the phase angle difference between the current peak and voltage peak in an AC power system. For example; in a typical factory the majority of loads are motors, which are inductive loads. Voltage leads current in an inductive circuit [ELI the ICE Man]. If the voltage waveform peak is used as the reference or zero degrees, the current wave form will peak around 30 to 40 degrees after the voltage peak. The difference between these peaks, in degrees, is the phase angle. Take the cosine of the phase angle and that's the power factor.
The formula for KW, three phase system, is [voltage]*[current]*[1.73]*[power factor]
The formula for KVAR, three phase system, is [voltage]*[current]*[1.73]*[sine of the phase angle]
Once you get the power factor or cosine of the phase angle from the motor manufacturer, take the arccos [inverse cosine] and get the angle. Get the sine for that angle and plug the numbers in the KVAR formula to see what the current rating is for that contactor, if it was used to control a motor.
So, if you don't have any capacitor banks to power then maybe you should put these on e-Bay and throw a kegger. Get some use out of them...
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