in rush current

Hello,

First of all you principle is correct, when increasing the voltage the currend decreases this is directly refering to the Power formula (P=VI, where P is real power, V is voltgae and I is current). But your electrical equipment has a nameplate rating with this, parameters listed on the nameplate means that components are rate for that parameters only (with tolerance) in excess of that the equipment will malfuction or worst burn.

Example;

If you have motor rated 230 volts then you operate it in 380 volts, your motor will be burn. For the reason that you motor windings are rated only for 230 volts.

Layman example:

If you have 230 volts light bulb then you operate it in 380 volts you buld will be busted.

Therefore adjustion the avr of the generator form 380V to 440V is not the solutio.

To have much more possible solution, try to give me that information below.

1. Per phase current?

2. Type of loads connected in the system?

3. Type of Generator? (stand by duty? prime duty? continuous duty?)

Hope you find this in order.

You can also email me to my email addresses as follows:

bennegregsiman@yahoo.com

bsiman@meinhardt.com.ph

Regards,

Benn Siman

the system is 380/220 3phase 4 wire. u can produce the voltage 220 by connecting one line to ground. I used to connect the transformer 440/220v. in order to step up the out put voltage of generator from 380 to 440v. So that instead the in rush current taken from generator is Pmotor/440V Lesser compared to Pmotor/220V. still the voltage for motor is 220v be coz of the transformer. it means that inrush current will be absorbed by transformer and lessen atleast 50 precent of rush current in the generator side.

Hi Abmar, seems to me you got a problem with unbalance loading since your generator is Three phase and your load was single phase besides from it was an air compressor the starting current of this should be quite high somewhere like 45 to50 amps depending also to your compressor and your motor bearing that has to take into accounts.

I can't figure out why you said your generator output is 380 volts but why are loading 220 volts motor, Benn is right you will burn your motor. check also the connection of your motor maybe it was 220/440 and it was wired up connected to 440volts and not 220 volts, otherwise you already got a burned motor.

If it is wired connected 440, the adjustment of AVR will help a little bit but if your problem is only during the start up, i would suggest instead of investing step up transformer as you mentioning if i were you soft starter is the best.

Have you try to check in loading your air compressor alone with out any load if during the start up you still experience low voltage there was something wrong, maybe you are already in the maximum load when you are loading the compressor and the generator could not cope up the demand, then the speed will decrease, voltage will follows in fact including the frequency. that is why you are encountering under voltage as claimed.

rather than spending money on a transformer, it might be better to invest in a 3 phase motor to provide more torque. Also, as was mentioned, make sure that the compressor is unloading the head pressure on start-up. If you stick with a single phase motor, make sure all capacitors are working properly. Of course, using the correct voltage for the motor is necessary.

abmar; try connecting to a different phase the AVR phase would be best, raising the voltage to the 220 volt single phase motor will burn out the transformer or motor. with a 40 kva load on the genset you could have a tired or worn out engine driving the generator, try your air compressor only on the genset, with the other load off use the neutral and one of the phases r s t perry