High Power VSDS motor (Urgent)

[wimple]

Hi,

I need to size an Electric Motor (VSDS type) to drive centrifugal compressor. Required power at motor shaft is about 27 MW. Gearbox will be included between motor and compressor.

Is it better to go for 2 poles or 4 poles for this range of power as per referenced applications ?
It seems the available Voltage is 6.6 kV on site.

Thanks in advance for your feedback
Best regards
Wimple

 

[wimple]

The VSDS range is 60 - 105%

Thanks

 

[jraef]

Sorry, VSDS motor?

Acronym Definition
VSDS Vermont State Dental Society
VSDS Variable Speed Drive System
VSDS Video Symbology Display System
VSDS Velocity Selection by Doppler Shift

So ASS-u-Me-ing Variable Speed Drive System then, is the 60 - 105% referring to Speed? Current? Torque? Flow? Tribbles?

Is your gear ratio 1:1, 2:1, 3:1, 300:1, 3,000,000:1?


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[wimple]

jraef,

> VSDS Vermont State Dental Society
what relation with electric motor to drive Compressor??

> VSDS Video Symbology Display System
what relation with electric motor to drive Compressor??

>VSDS Velocity Selection by Doppler Shift
what relation with electric motor to drive Compressor??

where do we are here?

 

[jraef]

I was sarcastically pointing out that you were making me Google the term VSDS, assuming I would know what it meant. I like helping people, but I like doing it with full knowledge of what they have. Using cryptic acronyms that are not universally understood and leaving out other critical information gets in the way.


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[wimple]

The Motor required is a variable speed drive system - VSDS -.... 60-105% is speed range.... usually it falls in the 70-105% for compression. lower limit of 60% means oversize the converter and less efficiency...

By the way, what are the Pros/Cons to have this motor with two driving end shaft?

Rgds

 

[jraef]

lower limit of 60% means oversize the converter and less efficiency.

Why? What type of VSD are you planning to use? It wouldn't make much of a difference with a PWM inverter. Maybe with a Current Source inverter, but it depends a lot on your load profile.

On the other issue, are you saying that someone is specifying a motor with 2 drive shafts, one on each end? Typically that is done when you have two mechanical driven units, twin cage blowers are the most common thing that comes to my mind. But I've seen it done with centrifugal compressors in combined cycle applications where they have the compressor on one side and a turbine on the other, so I suppose that means it can be done with 2 compressors.

As to 2 pole or 4 pole, that is one for the mechanical side of the equation. A 2 pole motor of the same MW output will put out less shaft torque. So the role of the gearbox will be a determining factor.


"If I had eight hours to chop down a tree, I'd spend six sharpening my axe." -- Abraham Lincoln
For the best use of Eng-Tips, please click here -> faq731-376

 

[CuriousJohn]

Wimple. At what RPM does the compressor run, nominally?
Just as an aside PWM is Pulse Width Modulation which describes the type of Variable Speed Drive (VSD)also refered to as a VFD Variable Frequency Drive.

 

[ScottyUK]

At 27MW rating it is likely to be a current source drive for a synchronous motor in which case PWM doesn't really matter...

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If we learn from our mistakes I'm getting a great education!

 

[dpc]

I'd strongly recommend getting the compressor manufacturer involved, even if you have to pay them. This is a very large application so any advice you get from us should not be taken too seriously - I'd want to hire some expertise for something this big.

You should also be able to get some help from motor suppliers.

"Theory is when you know all and nothing works. Practice is when all works and nobody knows why. In this case we have put together theory and practice: nothing works... and nobody knows why! (Albert Einstein)

 

[ozmosis]

Wimple
I agree with dpc. Ask by all means but with an application rated 27MW, I'd be wanting to know a little more information than you have provided.

 

[wimple]

Hi all

Thks for feedback

jaref,

QUOTED /
As to 2 pole or 4 pole, that is one for the mechanical side of the equation. A 2 pole motor of the same MW output will put out less shaft torque. So the role of the gearbox will be a determining factor.
UNQUOTED/

here it is mechanical drive application. What do you mean by the role of the gearbox?

Thks
Rgds
Wimple

 

[ScottyUK]

For the same drive output frequency and motor power rating a two pole motor rotates at twice the speed of a four pole motor, but produces half the torque. Which suits your load best? All you have said so far is that this is a 27MW drive, but that could be anything from a cylindrical rotor high speed machine running at 3000 rpm or more through to a low speed salient pole type rotating at a hundred rpm or less.


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If we learn from our mistakes I'm getting a great education!