starting 2 -150 hp motors

[sokkerdude]

I have a piece of equipment that has 2-150 horse powere motors driving one fly wheel on a crusher. So if only one motor runs. Not only is it turning the fly wheel but the other motor. I am going to start the frist motor with a Baldor soft start starter and the second with an across line starter after the frist motor has fully started. My question is does any one know of any other way of starting both these motors? And is there any negative effect on the Baldor soft starter with respect to the powere factor when the second starter(the cross line) come in? This is all powered by a generator and I can hear a little change in the generator when each motor come on line. Thank You

 

[hillbilly]

Re: starting 2 -150 hp motors

are these motors starting under load (other than the flywheel inertia)?

 

[tony_psuee]

Re: starting 2 -150 hp motors

sokkerdude,

I'm not familiar with the Baldor product, is it a soft start with bypass, of soft start only. If it has bypass it will be acting as an ATL at full speed and the soft start electronics should be isolated when the second motor ATL kicks in.

Tony

 

[charlie tuna]

Re: starting 2 -150 hp motors

my own opinion ---ain't gonna work! - i think your gonna have to have them both on separate drives with the accelleration and decelleration rates matched -- otherwise there will constantly be times when one motor is pushing or pulling the other..... control signal should match or be common to both motors. i had a similar problem with two foam pumps pressurizing a common header and the pump without the drive would actually drive the pump with the drive in reverse at times.........

 

[jcormack]

Re: starting 2 -150 hp motors

For this to work properly the first motor's softstart must have a by-pass other wise the motors would not load-share equally due to the voltage drop across the SCR's - Why can't you softstart both motors at the same time ? Generator issue? I would Current limit the softstarts & do both motors at the same time & then bypass softstarts at full speed.

A VFD would be MUCH easier on the generator than an SCR reduced-voltage softstart - also less heat generated in the motor. Read the papers in IEEE, an extended start via SCR can be very hard on a motor from a thermal stand point(chopped waveforms, high currents for long period, current spikes, etc.) If variable speed not needed then the VFD could be bypassed as well.

Other options today could include magnetic couplings, or fluid couplings (althought fluid couplings don't do well in load share apps) You could also engage second motor with a Dodge CST or clutch.