Induction Motor become induction generator

[Mohsen1]

We have 3.3kV, 265 KW, 1484 RPM induction motor coupled with steam turbine, when speed increase more than synch. Speed (Is Motor will change to Induction generator to inject reactive power to 3.3kV Busbar),
what is status if speed become between 1484 to 1500 RPM,
How can know this current feed motor or inject Busbar from Current indication
Is any analog or digital AC current meter indicate negative or positive indication like DC current meter
If it available, please tell me type & manufacturer
Regards,

 

[electricpete]

It won't be just a current meter. It'll have to be a power meter with voltage and current inputs to sense the phase angle. I'm guessing that Yokogawa will have something like that.

 

[electricuwe]

Assuming that your induction machine is coupled to a 50 Hz grid the machine will draw reactive (inductive) power from the line. A small amount of active power will be drawn for covering the stator iron loss.

To operate the machine as generator (supply active power to the line) you will have to increase speed slightly above 1500rpm, about 1516rpm to get nominal power.

 

[Mohsen1]

Hi Gentlemen,
electricpete,
Thanks for your reply, I know about power meter or use reverse power protection and use it as alarm but my question about AC current meter
Is any analog or digital AC current meter, indicate negative or positive indication like DC current meter or not
Regards,

electricuwe,
Thanks for your reply, Actually our system drive Force Draft fan for Steam Boiler , they designed it for reliability (Two primover at same time)
My question ,
We have (power factor meter) at Incomer feeding this 3.3 kV Busbar, suppose it indicate 0.8 lag, what is the deviation in case our Induction Machine changed from Motor (P.F =?) to Generator (P.F =?), (assume other electrical loads at Same Busbar are constant)
Also, Is any analog or digital AC current meter, indicate negative or positive indication like DC current meter or not
Regards,

 

[electricpete]

looking at an ac current along (without reference to voltage), there is no positive or negative direction. Current reverses polarity twice per cycle. Therefore ac current cannot be defined as positive or negative without reference to a voltage. Even when voltage reference is available, there is a continuum of possible phase angles between voltage and current (not just two discrete phase angles corresponding to positive and negative). Therefore I don't think you will find any ac current meters with negative/positive scales. Power meters may fill this role since they account for the phase angle between current and voltage.

 

[electricuwe]

I fully agree with electricpete

 

[busbar]

A watt/var transducer may be appropriate for monitoring various modes [power ‘quadrants’] of machine operation. Exampli gratia,

http://www.rochester.com/Pdf/wv15.pdf

 

[jwerthman]

I agree with the previous comments. Some type of power measuring instrument is necessary to determine the direction of power flow.

It sounds from your posts like you are expecting the induction generator to provide some reactive power to the system to lower the power factor. This will definitely not be the case, in fact, just the opposite. No matter which direction the real power (kW) is flowing (from the generator or to the motor), the induction generator or motor will always consume reactive power from the system. It is not like a synchronous motor that can be adjusted to either generate or consume reactive power by varying the field voltage. An induction generator always consumes reactive power.

 

[Mohsen1]

Thanks for all comments,
Can anyone give me Internent sites (more details about Induction Generators)

Regards,

 

[FARHADS]

HI MOHSEN1
WHERE DO YOU LIVE ?
I THINK YOU LIVE IN IRAN

 

[Mohsen1]

FARHADS
Thanks for your interest but I'm not from Iran

 

[jbartos]

Suggestion: Visit

http://www.yokogawa.com/TR/pdf/English/No31/P34_37.pdf

for a reverse power meter in addition to other mearuring functions. It includes its description and schematics.

 

[jbartos]

Small encore: Visit

http://www.avointl.com/software/powerquality/PA9 Rev I 3-01.pdf

for Power Flow direction metering option.

 

[Mohsen1]

Jbartos,

Thanks for your comment,

It is useful for synchronous Machine

Please if anybody has an idea about application (in Industry) of Induction generator, just send it

Thanks

 

[electricpete]

It's not clear what you're asking for. If you just want general info on inducatio generators then search through old threads. There are many links from there.
Here's a start:
thread237-23474
thread237-26511

 

[busbar]

Possibly:

http://www.pge.com/tariffs/advice/tariffsheets/17365-17420.doc

 

[jbartos]

Suggestion: Visit

http://www.narragansett.com/filelib/pdf/ri_interconnection_policy_v1.pdf

for bi-directional metering,

http://www.thomasregister.com

and search for kWhr meters (bi-directional), e.g. check with
Meterman Supply Inc.
11890-R Old Baltimore Pike
Beltsville, MD 20705
USA
Tel: 800-936-6403
Fax: 301-595-1065
Product Description
Dist. Of Electric Submeters, Current & Potential Transformers, Sockets & Enclosures For National Meter Industries, E-Mon, Schlumberger, Global Power Products, T&B, Osaki, Landis, Gyr