Star Delta Starter?

mosama

Member
Join Date
May 2009
Location
Egypt
Posts
182
Hi every one

What is the basis on which a motor star/delta starter is chosen?
I mean is it necessary to use star delta with every motor ?
and what are the correct rules for sizing contactors, overloads and circuit breakers for a star delta circuit?

Regards
 
Hello mosama.

There are two reasons why one would chose to use a star-delta starter.
1. To reduce the current peak when starting a large asyncronous AC motor.
2. To reduce the torque at the moment of startup. This to avoid mechanical damage or wear.

How to dimension star delta starter:
http://www.plctalk.com/qanda/showthread.php?t=30552

Nowadays, the smallest star-delta starters are dropped in favor of low-cost soft-starters.
 
Thanks JesperMP for your very quick reply

So I use star delta with every motor or there is a limit for motor KW to use star delta?
 
So I use star delta with every moto[..]
As long as there are all 6 leads from the 3 windings are available in the motor terminal box, then you can start by star-delta. But that does not mean you must. It depends on if you have to limit the current peak or the torque.

[..] or there is a limit for motor KW to use star delta?
In principle, there is no lower limit.
 
In some countries, the Star-Delta start is only used for motors over 5.5KW, but there are some applications, where a Star-Delta start should not be used (when you need high starting torque).
 

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