Can You Add a Soft-start Feature to a UNISAW?

[ken gibbs]

I have a rebuilt UNISAW 36-812. Its powered with a 3 hp 220v stock motor. I want to add a soft-start feature so it does not apply full power when you hit the red button. Questions:
1. Can this done without pulling down the motor?
2. Are there any engineering reasons why this would be harmful to the stater or windings if I add soft-start?

Any advice would be appreciated. Thanks.

Ken Gibbs

[Jason White]

Why would you want to?

I have a rebuilt UNISAW 36-812. Its powered with a 3 hp 220v stock motor. I want to add a soft-start feature so it does not apply full power when you hit the red button. Questions:
1. Can this done without pulling down the motor?
2. Are there any engineering reasons why this would be harmful to the stater or windings if I add soft-start?

Any advice would be appreciated. Thanks.

Ken Gibbs

[Mike Cruz]

DON'T put one on that makes the motor do anything BUT STOP the saw when you hit the RED button. The green one is a different story.

[Mike Heidrick]

Green means go
Red means stop

Add a 3-phase motor and VFD.

You can then controll the time it takes to come up to speed.

[Josiah Bartlett]

This would be easy with a 3 phase motor and variable speed drive (which can operate off 1ph power). Its a pain in the neck to do any other way.

[Sam Yerardi]

There are numerous companies that specialize in soft-start AC motor control. Here is one:

http://powerboss.s4i.net/


Judging from the cost of other motor controllers, vfds, that I specify as an electrical engineer, they won't be cheap. Consider the cost vs. benefit.

[Kyle Iwamoto]

I agree with Jason, why do it? The Uni turns on and off. What more could you want? Oh, sorry, soft start.

[Cliff Rohrabacher]

Yes but you may find the Leeson motor may not be compliant.
Ya might best contact Leeson or a motor repair expert


My single phase Hammer motors do that - sort of.
The require that I hold the start button in while the motor spins up.
The saw will spin up anyway the JP has such a heavy cutter head that I gotta do it their way.

I've run old school Blanchard grinders that are like that too. It is something to do with the Capacitors I am sure.

[Jason White]

I ask because I see the benefit with smaller portable and bench-top tools (routers, miter saws, etc.) because they can jerk and move when starting up, throwing off your accuracy and maybe even safety. But a cabinet saw is big and heavy -- not likely to move much when the blade starts spinning.

Jason

I agree with Jason, why do it? The Uni turns on and off. What more could you want? Oh, sorry, soft start.

[Ed Peters]

and amp draw is directly proportionate to thermal heat generation so I can't see anything good coming from extending this part of the cycle.

Just my $.02 and worth what it cost you.

Ed

[Mike Henderson]

and amp draw is directly proportionate to thermal heat generation so I can't see anything good coming from extending this part of the cycle.

Just my $.02 and worth what it cost you.

Ed

One thing soft start does is greatly reduce the current during startup.

Mike