Question about synchronous motor

[panter]

Hello everyone,

We have several 2 MV, 6KV synchronous motor which serves to drive the fan and we have occasionally technological delays which can last several days.
I have somewhat crazy ideaa that it then can be used like source of reactive power and then it should cover the consumption of reactive power in my big factory.
I think we should just separate the motor from the impeller and rotate it idling with controlled increased current excitation .
Does anyone have similar experiences or idea where it can go in a bad direction and make some sort of problem .

Thanks in advance

 

[zeusfaber]

You mean like a synchronous condenser?

 

[jraef]

So you don't need the fan, or are going to power the fan separately? Because if you power a 2MW fan with an induction motor, the newly added inductive load now makes your reactive power requirements higher. Remember, the likely REASON someone used a synch motor on that fan was to nor make the power factor worse. So if the fan is no longer needed, then making that motor into a synchronous condenser makes sense. If not, maybe not.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[zeusfaber]

My reading was that the fan motor was going to be diverted to PF control duty during outages of the process that needs the fan.

A.

 

[ScottyUK]

Dismounting a fan which requires a 2 MW main drive is going to far from a trivial undertaking.

For the economic case to work out either the reactive penaties must be astronomical where you are, or you employ slaves so you don't need to offset the cost of labour against whatever you save on the utility bill. ;-)

 

[jraef]

I think we should just separate the motor from the impeller and rotate it idling with controlled increased current excitation .

This is what led me to think this fan would be taken out of service. And note, ScottyUK, he didn't say remove it, I took that to mean simply decouple it.


"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington

 

[zeusfaber]

I should think some effort is going to have to be put into "safe system of work" issues if anybody needs to do anything to the rest of the plant while 2MW of fan drive is less shut down than it used to be.

A.

 

[panter]

First of all,
thanks for all responses
The idea is to this fan should be taken out of the service * when it is not required to work for days sometimes even weeks * and between motor and fan is coupling which can quickly be separated and to allow motor idling .

 

[ScottyUK]

If the cost of the labour to split and re-make the coupling is less than the value of the reactive energy that machine can compensate during the period where it is operating as a synchronous condenser then this idea would possibly make economic sense.

Do you have any way to regulate the machine field based on a VAR measurement so that the motor automatically adjusts to changing reactive demand, or is the reactive demand fairly constant?

 

[itsmoked]

The other question is whether your utility will give you any break on your power bill for quasi-random power factor changes. I believe they usually hammer you for a whole month for a single power factor transgression.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

That's the demand charges. Time was when the monthly KWHr consumption and the monthly KVARHr consumption were used to calculate the power factor charges per month. Now, with smart meters, some utilities charge for both leading and lagging KVARHrs if they exceed the threshold.
Demand charges on the other hand; I have seen tariffs even more stringent than you suggest. I have seen tariffs that persisted for a year after one short transgression.
The major part of those bills were typically about one half consumption and one half demand charges. If you had a demand transgression that pushed your demand to 3 times your normal demand, it would double your bill for that month and incur charges into the future.
Even if a plant went out of business, closed down and had the electric service disconnected, they would still be liable for demand charges for the next year.

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

 

[itsmoked]

Ah yes Bill, the definition of why "monopolies suck".

Keith Cress
kcress -

http://www.flaminsystems.com