Application of Soft Starters

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spsnyder

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Does anyone know a good source of information as to what applications are approriate for soft starters. I am trying to determine if soft starters would be economical and logical for well pumps of various horsepowers and haven't found a good resource. Thank you for any advice you have.

Scott
 
Re: Application of Soft Starters

We use them for large fire pumps, it helps keep the size of the generator down.
 
Re: Application of Soft Starters

You would need to consider the electrical rate that the customer is being billed. If is a
KW rate the starter would not make any difference
as far as a demand charge. If the rate is KVA there might be a very slight advantage. Also need the number of starts per day. Normally a starter is used to reduce the voltage drop due to inrush current. Smaller HP motors would not need the starter.
 
Re: Application of Soft Starters

I would think a well pump would be a good application for a soft starter if the motor is very large. Is this for domestic water supply? We once put one on a 200HP motor driving a pump going to a 16" water main.

Advantages are lower inrush current for the motor during starting, less wear and tear on the pump, and less water hammer. When a well pump starts there is almost no load on the motor, so it starts with a sudden jerk. The load increases as the pump lifts the water up the shaft.

Make sure someone programs the soft starter before running it.

Steve
 
Re: Application of Soft Starters

Thank you very much for your inputs. That's what I've found in the literature. The well pumps are 15, 10, and 5 HP with 6" discharges. I haven't been able to find any rules of thumb on number of starts per day, sizes of the motors, etc. for the correct application of soft starters.

What kind of programming is required for the soft starter? Time to ramp up? Thanks again.

Scott
 
Re: Application of Soft Starters

Time to ramp up and amount of torque are programmable. It seems like most are shipped set up for maximum torque, and sometimes that causes problems. We had a AHU that kept throwing belts and tripping breakers. It was actually a VFD, but soft starters have some of the same programming parameters. Another one wasn't programmed, and a fire ball shot out of the disconnect when the motor was started (the well pump was locked up too.)

Some of the better ones have programmable overload protection too. And some have a pump starting curve setting.

Steve
 
Re: Application of Soft Starters

Steve,

Thank you very much for the information and advise. It's been a big help.

Scott
 
Re: Application of Soft Starters

A well pump would be an excellent application for a soft start. Make sure you purchase the SS with a pump control option, we just started up a new pump station with 2 75 hp softstarts, but they were not ordered with a the pump control option so it was soft start and cost to stop instead of ramp to stop.
typically a deep well is done with a pump control valve that is initially open, when the pump starts it slowly closes to expell any air and eliminate a line surge. When stopping the process is reversed. There can be problems with the pump control vavles, some are not very reliable. Its important to understand the mechnical operation as well as the electrical operation. You'll may need a surge anticipator valve on the discharge piping, as when power is lost there can be a large hydraulic pressure wave and it can blow apart piping.
Soft starts are coming down in price and up in features.
Another advantage is reduced power inrush. I have a pending 100hp submersible installation, that if we used across the line starting it would require a 300 kva transfromer from the POCO, with a ss it would only be a 100 kva, and of course we have to pay for the connection costs, so the SS made sense.
We have done several waste water lift stations with softstarts on smaller pumps such as 5 hp, they work very well.
Plus ss are very more interesting to set up and program.
 
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