A guide to the connection and wiring of Low voltage 710kw motor, 1000Amps, 743rpm, 550VAC 2

[Eng_Jojo]

Hie Enginees, how do i connect a 710kw motor, nameplate says it draws 1000 A, 550VAC and has 743rpm. What is the first step, please help, The motor is to be used to drive a ball mill to crush gold ore.

 

[che12345]

For AC3 at 550V 1000A would exceed most LV contactor rating. You may use 1600A or higher rating ACB as a DOL contactor. Attention: ACB and 710kW motors are NOT designed for frequent/high frequency of operation.
Che Kuan Yau (Singapore)

 

[waross]

The first step is to hire an expert.

Is your national supply at 50 Hz or 60 Hz.
Do have your own generators?
743 RPM at 550 Volts suggests a high slip motor out of Canada.
Even if the motor is able to start the mill with Direct-On-Line starting, you will need about 2 MVA of generator capacity to start on generators.
Reduced current will both make the motor easier to start and allow the motor to start on a smaller generator.
Like I said, you need an expert.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[jraef]

Do you have 600V available for this? If not, that complicated things to a great degree.

Ball mills often need the ability to do inching so that you can align access hatches. That is VERY difficult to do with Across-The-Line starting. Some Solid State Soft Starters are capable of this function, I highly suggest looking into those. But make sure it is a “real” published feature, not some sort of salesperson’s statement of “Sure, we can do that”…. Those things rarely work out well.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[waross]

Jeff; Do you remember that video someone posted of the mechanical inverter used for inching? It featured an inching arrangement built with contactors?
It showed a wall of contactors banging and flashing. I guess it worked.


--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[waross]

Hi Jeff, again;
I suspect that the OP is in a country with such a poor grid reliability that they are using onsite generators.
If that is the case then some "off the wall" starting methods may be available.
Good call on the inching.
I missed that.
My experience with ore mills was with a lineup of 6000 HP autogenous mills.
AFAIK they didn't have hatches nor a need for inching.

--------------------
Ohm's law
Not just a good idea;
It's the LAW!

 

[electricpete]

I know it's a huge low speed thing, but if it has rolling bearings, I'll bet strap wrench / chain wrench and (if needed) cheater bar would suffice for inching.

Sleeve bearings on the other hand can be pretty darned tough to break loose once they lose their oil film while shutdown. We have succeeded in manually rotating a 7000hp 3600rpm horizontal coupled pump/motor, both with sleeve bearings, using a chain wrench / cheater bar combination, but it sure wasn't easy.

Funny story, we used so much force on a cheater bar once that we actually bent our chain wrench handle while trying to break loose and rotate a 4000hp 400rpm-ish vertical motor with Kingsbury thrust bearings. We knew something was wrong, after all the machine had coasted down smoothly a day beforehand (although it had been vibrating excessively while running, which is the reason we were trying to manually rotate as a first step in troubleshooting). Then I realized, the motor had an anti-reverse-rotation device....

Spoiler

If you guessed we were trying to rotate the wrong way, you'd be correct... but don't tell anybody!

 

[LionelHutz]

Hire an expert is still the first step.