Softstarters

[Cow]

I need some help choosing a softstart for a customer. He has a portable grain auger with a 20HP and 7.5HP motor on it. I've installed quite a few drives but never a softstarter yet so I'm pretty unfamiliar with them.

Is it possible to buy one 30HP softstart and add a couple manual motor protectors to protect each of the motors? What about adding a shunt trip bypass contactor to the setup? Or just let the softstarter carry the load full time?

Thanks guys.

 

[Finite10]

Are you talking about a Primary Resistor Type motor starter?
(I used to own acreage in Christmas Valley, is that near you?)

 

[masterinbama]

ABB and Allen Bradley both make soft starters with run contactors. As far as one starter for 2 motors I would go with separate starters.

 

[jim dungar]

A soft-starter is basically a variable voltage source. Yes you can feed multiple motors from a single soft-start, but you should not bring a motor on line once the soft-start is in run mode (this is called slamming, and can cause problems just like it does with VFDs).

In general the SCR's of a soft-start will generate losses of about 1.5watt/amp, so a bypass contactor is a good idea.

 

[Cow]

Thanks for the replies everyone.

Are you talking about a Primary Resistor Type motor starter?

(I used to own acreage in Christmas Valley, is that near you?)

?? I've never heard those terms before....

I live in the Hermiston-Pendleton area, Christmas Valley is a few hours away.

 

[Finite10]

I've never installed one. It's just in my Industrial Motor Control book, 3rd edition. Here's one for 99 cents.
On page 270 they say this;

They reduce POCO demand, less POCO line disturbance, and lowers your feeder inrush current. It also gives a gradual speed up.
Resistors are in series with motor lead. There's a Vd across the resistor and reduced V to motor. That reduces start speed and I.

As it gets up to sped, the I through the resistor decreases and that decreases the Vd.
E=IR
...and increases V to motor.

At speed, the resistor is cut out of the ckt.

 

[dbuckley]

When I was a kid, motor starting meant one of these things:

Yes, all exposed. often with a knife switch there for good measure too...

Hat tip to Wikipedia for the image.