I need info on a quality soft-start for a 15hp, 460v, 3phase pump motor.

Would like to have speed control, as well as the soft-start. Are there any with simple controls?

Most of our installed VFDs (Allen-Bradley, ABB & Square D) are using 4-20ma signals for speed control.

This motor installation will not have that control, therefore I wasn't sure if a full fledged VFD was required, or if a soft-start had an operator setable speed option.

Thanks in advance for any info provided.

Rick Miell

 

Hi Rick

Well lets start here, a Soft Starter will only limit the shockload generated by your motor being transmitted to your load. a VFD(variable speed drive) will provide you with speed control, along with providing you with soft starting as well.

I will assume that you are using a centrifical pump, these style of pumps do not pose any real load to a motor until they are nealy up to full speed. thus using a soft starter on them is not really needed.

Look up your DANFOSS rep, ask him for details on their 2800 series drives that should do the job for you. Here is a tip if the pump is centrifical and I mean only centrifical use one of their drives suitable for the HVAC industry. You will have good preformance and save money as well.

Danfoss drives have a function where you can use switch contacts to select various speeds......

regards
Matthew

 

You cannot do any speed control with a soft start. It only changes the voltage for the purpose of reducing torque and/or current during start, but without changing the frequency the motor will overheat eventually (within minutes). If all you want is to avoid water hammer on your pump, a soft start is still a good choice because it will cost 1/5 the price of an equivalent VFD. If you need to change speed, a VFD is the only thing that will work.

Suggestion for either, Motortronics.

 

Soft-Start controllers really do not control speed. A VFD will provide both functions for you. You do not need a 4-20ma speed reference to select an operating speed as most drives can be configured to operate a selectable fixed speed.

R. Webber

 

SquareD Altivar 28 Series. You can get kit that provides a speed potentiometer and run/stop controls right on the front of the drive.

ATV28HD16N4U AC DRIVE 400/460V 15 HP