Problem With Simultaneous Use of Generator and Motor

What is this VFD Unit you are talking about and do you go about to connect it if available and secondly can wrong connection of the Mains cable cause the motor to read high Amps?

The term VFD is an abbreviation for Variable Speed Drive. It is a piece of electronic equipment that can be programmed to start a 3 Ø motor slowly, and if correctly programmed will enable the selected generator to start the selected motor. They are available off-the-shelf in many places and retail outlets on the web are manifold.

The problem is very unlikely to be related to the way the mains cabling is connected, as any problem would reveal itself by opening the circuit protection device(s).

GA from me......Well described as well.

How did you come to conclusion earlier that it was happening due to moisture?

110KW in what mode star or delta?

How your panel is starting motor with star or delta?did you checked?

whats the starting load on motor?

Is motor picking it rated speed? if yes in what time?

Did you tried motor by removing coupled load on it?

Did you checked actual motor current with a clamp tester on each phase?

In answering to your question, the area were the motor is house was overflooded with water thus covering the motor and it was switch on after the water had been clear failng to service the motor, thats brought about its rewinding.11okw is at the mode of 380-415v. The panel starts motor by switching on with a press botton for Star and after 4sec or what ever sec you set it its switch over to Delta state and the starting load is 223amp. It does not run to its pick speed after which the Generator goes down, but during that starting time we check each of the cable with a Clamp meter and also the Panel Amp meter indicates the same amperage as the Clamp On meter 360amp

Respected sir,

Thank you very much for your guidance.

I come to know the factors to be consirdered.

Thanking you.

S.S. Magdum

A 110kw motor will have an average of full load current of 150A. Now that at starting it will require atleast 4 times its full load current. Hence only a Genset rated 600A and above will be able to handle it

General rule of thumb in selection of DG sets for motor application, the starting current of the motor should not exceed 2 times the full load current of the DG set.

May be in your case while 110 kw motor starts the the starting current is more and in effect the DG set is bound to deliver more than 2 times the full load current, in which case there will be voltage dip and motor trips.

The question is:

Did the generator work with the generator before the unit was flooded?

If the answer is yes, then what is damaged that was allowing it to come on line before the flood? I would look for a capacitor bank or some sort of control device.

If the answer is no, then read what everyone else is trying to tell you.

I agree with Tcmtech, good answer by the way, but remember he stated you could use a VFD or some other method of soft start or ramping up. A soft start device could be less expensive than a VFD and might be better suited to a genset type setup.

A fairly simple thing you could try is to use an uncoupled motor as a flywheel. A running motor will have an amount of stored energy proportional to its stator magnetic field and its mechanical inertia. When the second motor is started the first will help to supply a small part of the inrush current. Plus having a load on your generator will get the governor up off of minimum. Most gen-sets are very sluggish and sometimes even sticky when they are at minimum output.

Gentlemen thanks for your valuable contributions, as they help me a lot arriving at a conclution after series of test. The Generator can not withstand the starting torque/starting current of the motor. its small for the motor.

The said motor had never been run with the 250KVA Gen.set. Its only after it had been flooded with water that they try to switch it, when open its still fill with water. Now that it has been rewind, I switch on/off, on/off, three times and on the fourth tme after it gain its speeds, it run it for 4-5 minutes then Gen.set start to go down gradually, then OFF.

Our recommendation is to go for 500KVA -- 650KVA Generator when considered the rapid growing of the company