Soft Starters

http://www.google.com/search?sourceid=navclient&ie=UTF-8&rlz=1T4GGLL_en&q=Soft+Starters+%26+how+does+it+contribute+in+energy+efficiency%3f

u search it from google

As has been told by the previous answerers, there are plenty of sites tecahing you much on Soft Starters. But, be clear on one thing:

Soft Starters do not help to achieve any energy savings. They are in line only during starting.

electricalexpert65 said

"Soft Starters do not help to achieve any energy savings. They are in line only during starting"

Not exactly correct.

They limit starting amps - this saves you a lot on "demand charges" from your local utility.

A NEMA B motor can easily draw 600% FLA on a across the line start. A soft start will limit this to maybe 250% or so. A soft start will also lower wear on other drive components such as reducers, chains, belts, etc.

A VFD is usually a much better choice than a stand alone soft starter and it can save a considerable amount of energy depending on the application. Also many utilities - at least in the US- offer considerable rebates if you purchase a VFD and premium efficiency motor. Edmund

"They limit starting amps - this saves you a lot on "demand charges" from your local utility."

No, sorry. Not true in 99%* of cases. Almost all utilities use what is called a "Sliding Demand Window" to calculate your demand charges. 15 minutes is very common, some use 20 minutes or even 30 minutes. In any case, a spike in current that lasts less than the demand window will have no effect of the peak demand. So even though an across the line start may cause a 600% current spike, the Demand Meter will not register it.

This is a very common misconception used by salesmen to sell soft starters because they do not possess the talent or knowledge to sell them on their numerous other benefits. When I was in the soft starter business, I always instructed my salesmen to avoid this approach. But because most people have no clue as to how they are billed for electricity, it's an easy scam to close a sale and sooner or later a hungry salesman will resort to it. Unfortunate, but true.

Don't believe me? Ask your utility!

* I say 99% because in my 30 year career in soft starters, I found exactly 2 utilities that used instantaneous demand metering. They got away with it because they were small secondary suppliers (i.e. no generation of their own, they bought power from larger suppliers) with a few industrial contracts and a large base of residential rate payers who sat on the governing board, meaning their industrial customers were forced to pay the exorbitant demand charges and had no choice and no voice.

JRaef is right. I agree with JReaf 100%

Search for ABB Softstarter Handbook, freely available on internet. Thats a good handbook to understand motor starter methods.

library.abb.com/global/scot/scot209.nsf/.../$file/1sfc132002m0201.pdf

1. Iam a marine engineer and can explain only about marine power installations.Soft starter use thyristors for reducing starting current surge.Gate signals are used to fire thyristors for reducing starting current.
2. Yes,soft starters can be extended to power manager.Normally done so in electric propulsion.The method to start and control propulsion motors cannot be exactly called soft start because they sre synchronus motors.But still the concept is same.

sailer666

http://en.wikipedia.org/wiki/Motor_soft_starter