For my proposed new aluminium extrusion factory I ve the load of 250 kw heater and 670 HP of motors.Whats the kva rating of the transformer I should go for?Pls advice.
The total load is around 750kW but allowing for low power factor on the motors I would suggest you make it 1000kVA' get that or the next size up transformer off the shelf. Fit automatic power factor correction to reduce the load and save money.
Your connected load is about 250 kW plus about another 700 kW (from the motors when taking into account efficency and Power Factor). So the total connected load is just under 1000 kw. This 1000 kw is about 1 MegaWatt ( MW). A MegaWatt is 1000 kW You want to oversize your transformer, to account for added load at a later time as well. If I was ordering the transformer, I would be looking at one to cover at least a 1.5 MW. This would be roughly a 1,500 kVA transformer. You could order one slightly smaller, and add cooling fans which come on at max loads to cool down the transformer and increase its kVA rating. Because you have a large motor load, you will likely need the full 1500 kVA unit, because of the Power Factor issues with motor loads. BTW --- there may be a 1 year lead time on ordering a transformer that size.
the kva rating of the transformer shows that the power factor of the load has been taken care of
