Reverse Power (MW) disipation in mining winder motor 9

[jazzytoo]

Hello Experts,

I am installing three 2.5 MW backup generators for a mining company. The generator will be used to backup the mines when the utility grid is not available, which will occur more frequently and for longer durations due to the utility's undersized capacity coupled with extreme growth. The motor on the Double Drum Vertical Shaft Winder gives out 6 MW of reverse power, when the winder motor is slowing down to a stop at the bottom depth of the 980-meter mine. I cannot use reverse power relay to protect the generator, because the winder will be carrying miners and an outage on the generator will put the miners' lives at risk. How can I dissipate the reverse power without disconnecting the generator?

 

[davidbeach]

You need a resistor bank that can be switched in during regeneration by the load so that the resistors can absorb the power generated by the hoist. Another alternative would be to drive the hoist with a VFD that includes a braking resistor. You don't want a drive that would export power back to the generators.

 

[waross]

I am worried about a winder motor that develops 6 MW of reverse power running on one or two or even three 2.5 MW generators.
You will need a resistor capable of absorbing 6 MW of regenerated power. I have to wonder how you are going to start that motor on only three 2.5 MW sets?
Are you sure that the motor is developing 6 MW of reverse power?
If you don't have sufficient resistor capacity to absorb the reverse power, the falling cage will accelerate and as it does, it will motor the generator and overspeed the generator and diesel engine, possibly to destruction.
How do you protect the cage now in the event of a power failure?


Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[itsmoked]

Of topic a bit: It's a real shame that much energy would be getting dumped. Are there no rotating storage systems available? Big flywheeled induction motor/generator.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[jazzytoo]

davidbeach, woross and itsmoked,

Thank you so much for your helpful advice. Your knowledge and expertise are greatly appreciated.

Thanks,
jazzytoo

 

[FreddyNurk]

http://www.pcorp.com.au/images/pcorp-pdfs/powerstore-mining-hi-rez.pdf

shows a downloadable brochure that outlines almost exactly what itsmoked proposed. From memory the unit mentioned was installed in a grid connected situation and used to smooth out the winding load, also with generators running to provide extra grunt to operate the winder.

I don't know the exact details, and I have no current association with the company that manufactures them, but it could be worth looking into.

I agree completely with Waross, shifting the problem by not fitting a reverse power relay won't be suitable.

In situations where the grid hasn't got enough capacity, can you cogenerate onsite, or are there other distribution issues with the grid connection i.e. frequent 'line down' outages?

 

[jazzytoo]

Hello FredyNurk,

Thank you for your valuable feedback on the reverse power issue. We will evaluate the engineering and economic benefits of the COGEN option and discuss the option with the customer, if we find it to be a feasible solution option.

Thanks again,
jazzytoo