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jsaj
26-09-2009, 11:08 AM
any one can help how to size the resistors for a star delta start closed transition of 140HP screw semi hermetic compressor?

what will be the advantges and disadvantages of this type of starter compare to part winding start?

NoNickName
26-09-2009, 02:50 PM
http://www.lovatoelectric.com/images/Ima39.GIF ohms

Where Ue is the linked network voltage
Ie the MRA of the compressor

For the power of the resistors:
http://www.lovatoelectric.com/images/Ima40.GIF Watts

for max 12 starts per hour


Oh, EDIT: no advantages over PWS, but no other choice than star/delta start, as far as I know, for motors above 160HP.

jsaj
27-09-2009, 10:36 AM
thanks a lot. this will be a good help.:)

Magoo
28-09-2009, 12:21 AM
From memory, closed transition star delta starters had 4 contactors. Today soft starters with parallel line contactors or VSD's would be a less expensive option.
Carrier had closed transition star delta starters on large centrifigal chillers.400 HP plus, to reduce transition power spikes.
magoo