Starting 2 pole motors

[kjwudsph]

Hi, I'm a newbie here and I need help with starting some 2 pole 20KW motors, can I still use the normal 22KW DOL starters or is it better to upgrade the starters because of the larger starting current - any advice would be gratefully received, Thanks kjwudsph

 

[Marvo]

A 22 kW DOL starter would be quite a design. I've never seen DOL starters used above 7.5kW to be honest, the start current would be extremely high and prolonged and the starting torque would be very low especially with a 2-pole motor.

Why not a star-delta starter or even a soft starter/ VFD?

 

[MDJ]

, can I still use the normal 22KW DOL starters

? 22 kw

 

[Darkwood]

I have 37.5Kw starting DOL ... Old Russian lathes.... its your supply that denotes the need for restricted starting currents having said that a motor 4kw or higher really wants to be looking at some form of soft starting if its on a 100amp incoming supply as they can give excessive mains transients while starting up and the DNO look dimly on such issues.

 

[moospark]

I can generally get a 2 stroke engine going, nee botha.

 

[Lucien Nunes]

And it also depends on the load the motor is driving, the number of starts per hour, the motor design etc. If the motor starts a low-inertia load infrequently and the supply is large enough, you can get away with it, however a full understanding of the operating conditions is needed to give any useful advice on this.

 

[Darkwood]

Too right Nunes had a firm call me out who had DNO come down hard on them found they were inching 30kw motors and dipping the whole neighbourhood - a nice little Inverter install for me

 

[Lucien Nunes]

In the days before inverters sounds like it would have been a job for a geared down pony motor. Or else, Klunk-Klonk. Klunk-Klonk. Klunk-klonk, the sound of 80A contactors wearing out quickly.

 

[Darkwood]

You nailed it the contactor had recently been changed for that very reason ....klunk klunk klunk klunk then RUN .... grrrrrr Trip blown contact points phase out. It had already had a replacement contactor only 2months prior to me going out to it.