Soft start for a Cat 3535

[Axxlrod]

I have a Cat 3535 pump with a 25hp motor. Wired at 230v. Standard mag starter on the motor. This pump/motor combo originally came with a touchless auto that I had at my wash. I've since put in a conveyor tunnel, but still use the same cat pump/motor to power the hp rinse arch.

I'm re-doing my wash packages, and adding the hp option to more packages, so it will be used more often.

I'm thinking it would be beneficial to swap the mag starter out for a soft start.

Do any of you touchless operators have a soft start on your large pump motors?

Any recommendations where to buy one?

Thanks.

 

[MEP001]

automationdirect.com has what you need and has the support to help you use it.

 

[Axxlrod]

Great website MEP.

I just input my motor specs into the finder tool on that website. The recommended soft-start is $2106! Yikes.

 

[washnvac]

I use Allen-Bradley SMC-3 units for my 15 hp dryer motors. They were about $1100 each a few years ago. They have lots of settings to adjust to your needs. In my case, I needed to limit my start up amps so as not to exceed the transformer rating on site. I had added a second auto with dryers, and the cost of upgrading service to 600 amps was out of site. Using the soft starts allowed me to stay with the 400 amp service with no other modifications.

 

[xcite]

Look into a VFD from automation direct instead. Then you can ramp up the motor slowly and maximize your savings.

 

[Axxlrod]

Isn't that what a soft-start does?

I have vfd's on other motors like for blowers because they are programmed to do some trick things like varying speed between cars.

I doubt I'd ever need to vary the motor speed on a hp pump. VFD seems like it would be overkill.

 

[xcite]

Soft starts only limit amps to a point VFD's can start the ramping right from the start. Plus a Dura Pulse 25 hp 230v VFD is only 1370.00

 

[MEP001]

I doubt I'd ever need to vary the motor speed on a hp pump. VFD seems like it would be overkill.

VFDs can also ramp up a motor to reduce start-up load or mechanical wear and tear, plus if you do an RPM check on your pump you might find it's turning faster than necessary. I've found a lot of the time pumps are running a good bit faster than they need to. I looked at someone's D&S 5000 once because it kept tripping the breaker, turned out he had just changed the regulator and had tightened it all the way down. The unit was running 2200 PSI because it was pumping 15% over its rated capacity all the time.

 

[Greg Pack]

A VFD would give lots of options. You could get fancy and install pressure sensors with PLC and ramp the rpms up and down according to demand.

 

[Axxlrod]

That's the thing. I don't want fancy. I'm a KISS kinda guy.

Just looking for a simple solution to reduce the electrical demand from the 25hp motor.

 

[MEP001]

The VFD can still be used for a simple soft start.

 

[Greg Pack]

The VFD can still be used for a simple soft start.

Not only that, but on most VFDs a change of the motor speed is a simple push of the "up" or "down" button. So for example you can figure out that for the pressure you need out of the pump you have to run the motor at say 45 hz. So it will start slow AND run at a slower RPM. If you run a pump motor at full speed all that excess energy will just be dumped out through the regulator.

 

[br549ms]

A Soft Start may not work for the pump, most pumps are loaded at startup, making it difficult to have a power reduction to the motor. A 25hp soft start or VFD will be costly. I doubt you will see a ROI even if you can dial it in.

 

[wash4me]

Demand is figured on a 15 or 30 minute average most places so a soft start or vfd won’t help. It will help with motor overheating from excessive starts, also extend pump and belt life and change speeds if you put in a vfd.