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HHung
Member

Join Date: Jun 2009
Posts: 8

Motor Starter

09/08/2009 11:39 PM

Hi All,

I am looking for some guidance, code, practice discussing starting methods applied for induction motors depending on different application, rating of motor, RPM, torque .....I mean how we make dicision to use soft start, VFD or Wye-delta ...Highly appreciate any suggestion/advice. Any link to provide some theory would be helpful.

Thanks

HH
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Sapper
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Join Date: Dec 2007
Location: Sydney Australia
Posts: 480
Good Answers: 35
#1

Re: Motor starter

09/09/2009 1:02 AM

This looks like a homework alert...

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msamad
Guru

Join Date: Feb 2009
Location: Houston, USA
Posts: 946
Good Answers: 244
#2
In reply to #1

Re: Motor starter

09/09/2009 10:17 PM

This is a good document for this help:

http://www.automation.schneider-electric.com/as-guide/EN/pdf_files/asg-4-motor-starting-and-protection.pdf

- MS

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rabat
Commentator

Join Date: Sep 2009
Posts: 59
#3

Re: Motor Starter

09/10/2009 3:44 AM

Soft starts Pros/Cons

1. Pros:Soft starts are way cheaper than VFD. Use Cutler and Hammer or Square D.

2. You must know your application. If the electrical grid can't provide the juice for your soft start don't use it. Soft start require alot of inrush current to get the motor to full speed. Flicker is your common issue.

3. Cons: You only can start motor maybe 3-4 times in an hour. It you need to start more than that switch to VFDs. The windings on the soft start get really hot quick and well lock you out if you exceed a certain amount of starts or temperature. Again know your application.

VFDs Pros/Cons

1. Pro: Use VFDs when your trying to control flow or level in a tank, well, channel, etc...

2. Most client I work with have the $$$ and typical I always see VFDs around water treatment and waste water treatment plants.
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