SOFT START for Servo Motors

[Gymnast]

I have seen, that the servo motors have a slow start function, that you can set by a software parameter. It controls how fast the motor should increase speed to the lowest constant speed, that it can make (typically 100 RPM or 200 RPM).

[sbrownn]

5 hours ago, Gymnast said:

I have seen, that the servo motors have a slow start function, that you can set by a software parameter. It controls how fast the motor should increase speed to the lowest constant speed, that it can make (typically 100 RPM or 200 RPM).

I hadn't realized that. Good to know.  Thanks!

[DonInReno]

20 hours ago, Constabulary said:

Don, my original idea (or brain fart) was this thingy here which goes into single phase table saws:

That’s a nice simple solution.  Let us know how it works out.   I have a portable Mikita table saw that doesn’t have soft start and it would be nice to calm it down.

[Primosand]

Constabulary I'm not clear why you are considering this "soft start" for your servo. But if it is because your servo starts and stops abruptly I had this abrupt start/stop problem on my first and second servo motor. Both were Consew 550 watt servos. To get around this issue or to get the motor to start smoothly (stopping abruptly didn't really bother me) I opened up the end of the motor and disabled the little brake. I just took the brake pads out of the first one to see if that would fix the issue. It did. On the second servo (same brand and model) I think I took the arm off and that also worked. I use a speed reducer as well but now I can start out at apostate zero and feather it up to whatever sewing speed I need without any jump or lurch. Again I'm not sure this is what were were getting at but your question reminded me I needed to do this back when I switched to servo motors.

[Constabulary]

Again - it was just a brain fart. The idea was that the above linked soft start module possibly could add some sort of acceleration ramp to a servo motor without speed reducer. I´m not meaning the lowest rpm a servo starts with I mean a slightly smoother start / rpm acceleration when you hit the pedal. I personally don´t have the need cause I´m using speed reducers. It was just an idea because I´m in process of adding this module to my table saw and thought it possibly could add some comfort to one or another servo motor.

Again - just a wild idea and I though someone else here probably had a similar brain fart or maybe has some experience with this module in general - you never know.

 

EDIT:

My idea was just a softer start of certain (not all) servo motors and not preventing from tripping fuses and so on... Just a softer start, no RPM reduction...

So boobies can explain it better than I (different module - but same effect I was thinking to achieve)

https://www.youtube.com/watch?v=oSrz3GaaDO8

This was the table saw soft start module (or similar) I was thinking of:

https://www.youtube.com/watch?v=iWr0B2U-QT8

Note the difference when the motor starts.

 

 

 

 

Edited March 14, 2021 by Constabulary

[Kcstott]

13 hours ago, Constabulary said:

Again - it was just a brain fart. The idea was that the above linked soft start module possibly could add some sort of acceleration ramp to a servo motor without speed reducer. I´m not meaning the lowest rpm a servo starts with I mean a slightly smoother start / rpm acceleration when you hit the pedal. I personally don´t have the need cause I´m using speed reducers. It was just an idea because I´m in process of adding this module to my table saw and thought it possibly could add some comfort to one or another servo motor.

Again - just a wild idea and I though someone else here probably had a similar brain fart or maybe has some experience with this module in general - you never know.

 

EDIT:

My idea was just a softer start of certain (not all) servo motors and not preventing from tripping fuses and so on... Just a softer start, no RPM reduction...

So boobies can explain it better than I (different module - but same effect I was thinking to achieve)

https://www.youtube.com/watch?v=oSrz3GaaDO8

This was the table saw soft start module (or similar) I was thinking of:

https://www.youtube.com/watch?v=iWr0B2U-QT8

Note the difference when the motor starts.

1. Soft starts are garbage. They create far to much start up heat on a single phase squirrel cage motor. 
2. As mentioned above a servo motor is designed to have a servo speed control connected to it and appropriate throttle control. 
So that said what is needed to give a servo motor better start up control is a better speed control. Servo speed control units, A good one can cost $500 and up and require a separate DC power supply. The fact that we have an AC compatible servo motor with no external power supply for $300 is pretty amazing. 
What we need is analog input for control say a 0-10V from a potentiometer control. but now you need a second power supply a potentiometer and a new control. all that equals is not cheep. 

As to your table saw. I'd recommend a VFD and three phase motor. Then you can program ramp time and starting torque. far more robust then a soft start but also far more expensive too. installing a soft start to prevent breakers or fuses from popping is treating a symptom. You need to upgrade the service to the saw. 

 

 

 

 

Edited March 14, 2021 by Kcstott

[dikman]

I thought the "soft-start" modules were designed to work with universal brush-type motors? Squirrel cage induction motors are notoriously difficult to use with any form of speed control, which is why people change their lathes, belt grinders etc to 3-phase motors + VFD.

[Kcstott]

1 hour ago, dikman said:

I thought the "soft-start" modules were designed to work with universal brush-type motors? Squirrel cage induction motors are notoriously difficult to use with any form of speed control, which is why people change their lathes, belt grinders etc to 3-phase motors + VFD.

I've never seen a table saw with a brushed motor. The Universal brushed motors I've dealt with were fractional HP as in 1/10 HP. 
 

[Frodo]

Is this what you are  looking for?

German made soft start

ATS01N206QN

Model Type: Altistart 01

Altistart 01 Soft Starter Module

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Manufacturers
Schneider, Telemecanique

[dikman]

That's for 3-phase motors. If that youtube video is working on a single phase induction motor I'm curious how it does it. The instructions with my VFD's give connection details for using with single phase induction motors to vary their speed. I thought this would be great for my grinder but I did some research and yes, it will work BUT it isn't recommended! The motor won't develop much torque and it may overheat. Hence the need to go to 3-phase motors.

I just finished digging around for more soft-start info and Don's post about the Baldor unit is the key. That unit is intended to work on single-phase induction motors and the link explains how. The one that Constabulary linked to is doubtless the same type of unit, so I've learned something new. The Baldor information indicates that the soft-start unit needs to be matched to the power rating of the motor, so buying one at random could be a problem.

Edited March 15, 2021 by dikman
more info.