problem with motor

I need further info ,, is the new motor voltage is the same with the old one ? check that the frequency of new one you're using is equal to the electrical supply frequency .also give us the electrical power (K Watt) of the new one in order to decide if the starting current is normal or not .... initially my advice that when you have to replace a motor owing to any reason , then you use a motor with the same specification of the taken-away motor ....

The voltages you mention are unfamiliar to me. In star the windings should receive 1/√3 (~0.577) times the line (delta) voltage. 380/690 (~0.551) looks a bit off. I would recheck the wiring closely. Though not likely, it is conceivable that the contactors have been switched, which would start the motor in delta, giving the high inrush current.

Surprised to hear about a 380/690V induction delta/star motor, I only seen 380/660V ones.

Is the motor meant to run as a dekta-connected motor at 690V? DOL starting in Delta may give you an inrush of say 6X In. If so, in star mode while starting, it should take 2XIn only normally. What is it drawing? Much higher? Then something is wrong. It may take 2Xin for almost 90% of the starting time. Is this worrying you?

You don't say how big the motor is but going on some of the happenings around our plant this is what could be happening. Some of the smaller motors turning up at our plant are 3 phase 240V delta connection ONLY or 3 phase 415V star connection ONLY. By conecting it up to a star delta starter you may be wrong voltage to the windings. Please check the name place for this condition. It is particularly easy to miss if the original motor was 415V delta connected. Good luck.

sorry for not giving all the required information ,i will now try and list all the necessary information. my main problem is that the company that supplied the motor says that even though the motor has two voltages on the name plate, it is still designed to run star /delta . my plant power supply is 380 v 3 phase , i believe that because this motor has a higer voltage rating for star 660v .... i believe this is why i am having problems starting up in star or are they right ?????

1) original motor 25 hp ' new motor 22 kw '

2) start delta starter was originaly overated so there was no need to change

3)no name plate on original motor i got the hp from the user manual

i believe that the motor will deliver the rated HP when connected in Delta mode on 380V supply or in Star mode when connected on a 660V supply, this being 1.732 X 380V.

You are right in using a star-delta starting method, but you must supply ONLY 380V. So, when in star mode, it will draw 2XIn at inrush, and when it changes over to delta, it will draw In having accelerated and built up the back emf. It will also now deliver the rated power (22HP?)

Put it on a VFD

and forget about it.

I guess you just switch the motor on directly without any starting device. Normal three phase motor when suddenly supplied with energy could consume up to 15 times higher current than its max operating current. That calls for installation that could withstand such a huge current surges. Therefore many methods of starting up motors have been develop and the best is to install frequency inverter that that allows keeping current within that of max allowed so saves energy if frequent strating/stopping.

Te supplier is right. This is normal, but expensive to run.

Stan