Re: Motor starting jolt

John Griffin
 

Induction motors designed to deliver big starting torque (eg, compressor duty) can give a jolt when hooked up to something like a table saw or a lathe

eg, "The 1 HP LEESON Compressor Duty Electric Motor is a dependable and powerful single-phase motor designed especially for compressors requiring high breakdown torque and rugged mechanical construction. UL listed. CSA certified." 

LEESON Compressor Duty Electric Motor — 1 HP, 115/230V, 3600 RPM, Model# 110160



The issue is high inrush current. If you wired in a particularly stiff (high current) 115 VAC circuit in your shop, this will amplify the issue. One remedy is to wire from the outlet to the motor using a wire size and length calculated by the motor full load running current (on motor tag). This will dampen start up jolt.

The above motor is FL rated at about 13A. Just for grins, splice in a 25' - 50' roll of 14 AWG between 115 VAC outlet and motor then test. This approach would be a lot cheaper than a solid state soft start

On Sun, Dec 24, 2017 at 7:01 PM, Oren obolt@... [SOUTHBENDLATHE] <SOUTHBENDLATHE@...> wrote:
 

I’m thinking a soft starter would manage incoming line voltage but would not reduce the initial surge coming from the starting capacitor. I believe it’s that starting capacitor that generates the big jolt making the motor jump at startup. I could be totally wrong for sure as I’m over my head on this.



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