Can I use a soft starter on a 3-phase motor?

[Mark Gibney]

I put a 3-phase motor on a bandsaw. I'm waiting on delivery of the on / off switch, but I plugged it in to test run it and it runs great, but the start is really sudden, and the belt slips, screeching.

I read about soft starters that would bring the motor up to working speed more slowly.

Can I install one on my bandsaw?

Here's the motor nameplate

Screen Shot 2017-01-31 at 6.27.29 AM.jpg

And here's a link to the magnetic on / off switch

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

I'm hoping I can indeed install it, but any news good or bad is appreciated.

[Mike Heidrick]

Do you mean a VFD? Yes you can use a VFD with that motor. You will not put that switch between the VFD and motor though. The switch gets hooked to PLC contacts on the VFD. You need a 2.2kw 3hp VFD.

Id fix the belt first though. Should not be slipping.

[Leo Graywacz]

The switch you have there will work to turn it on and off. It likely won't stop the quick start problem you are having.

What you would want is a VFD which you can program to start the 3 phase motor slowly. Plus you can program it for a quicker stop. It would replace the magnetic starter switch.

[Mike Heidrick]

You can use a magnetic starter with a VFD as well if you want. Ideally you enclose a VFD with proper clearances and airflow while keeping it away from dust and debris.

[George Makra]

Yes there are soft starters but for the money it would be cheaper to put a VFD on it.
Belt slippage is a sign of loose or worn belts though.

[Wayne Lomman]

You just need a star delta switch. It is a two stage switch that starts on one or two phases in the first position until the revs build up when you switch to full power. This is the most common 3 phase switch I use. Beats the daylights out of a vfd for price. Also it keeps the starting amps low. Cheers

[Chris Hachet]

Interesting, had not thought of the star delta switch.

[Leo Graywacz]

I have never heard of a star delta switch

[George Makra]

It is used on large motors to limit current on start up.
A three hp motor does not warrant the effort to install one.

[Rod Sheridan]

You just need a star delta switch. It is a two stage switch that starts on one or two phases in the first position until the revs build up when you switch to full power. This is the most common 3 phase switch I use. Beats the daylights out of a vfd for price. Also it keeps the starting amps low. Cheers

A star/delta starter requires a 6 lead motor.

It does not start on two phases, as that single phases the motor and it won't rotate.

What it does is start the motor in WYE configuration, then once the motor is almost up to speed you switch to Delta.

Starting the motor in WYE configuration means that the motor voltage is only 58% which drastically reduces motor torque and current.

This isn't worth the effort on a motor this small, all it needs is good pulleys and a new belt.................Regards, Rod.

[Gil Kennedy]

Since the OPs motor is dual voltage, it must have 12 leads for WYE-Delta start. Most off the shelf dual voltage motors are 9 lead devices. Agree that this is not practical for such a small motor.

[Mark Gibney]

Thank you all - I'll take this information and run it by an electrician friend.

Thing is the belt and pulley are brand spanking new. The pulley has a smooth epoxy coating that contributes to the slipping - the slipping is only momentarily on start up. A machinist friend suggested using belt dressing to improve grip.

[Malcolm McLeod]

Thank you all - I'll take this information and run it by an electrician friend.

Thing is the belt and pulley are brand spanking new. The pulley has a smooth epoxy coating that contributes to the slipping - the slipping is only momentarily on start up. A machinist friend suggested using belt dressing to improve grip.

You didn't cite any details of the drive train, but is it possible that the motor has been up-sized and the pulleys/belt were not? Don't have a link handy, but there are lots of online belt/sheave sizing calculators. Make sure that the belt profile (A/B/C/D, etc...) can handle the full 3Hp of the motor. You might find that either a larger profile, or a multi-belt arrangement are required.

[David Kumm]

Or try a VX cogged belt. Better grip for that application. Dave

[terry mccammon]

Hmm, my bandsaw (3HP) also had belt squeak or chirp when I started it. It was high enough volume and shrill enough that I keep hearing protection at the saw to slip on when I started it. As it had been set up by the vendor prior to my owning it, I presumed, silly me, that it was correct. Upon deciding it was worth getting down on the floor and actually looking, the belt was not really adjusted correctly and that took care of it. Broken down old engineer lying on floor muttering was amusing to on lookers. Not so amusing for me.