Switching on/off vacuum motors
Switching on/off vacuum motors
(OP)
Hi,
A question bothers me for a while and haven't found an answer for it. Hope community knowledge will step up. :) People are saying that it is not good idea for high rpm motor to be switched on/off very often. Motor I am talking about is used for vacuum holding wood panels during cutting on a cnc machine. Owners rather use valve to turn on/off vacuum while load / unload panels than switch motors on/off.
Is there anything what may damage motor by repeating on/off cycle during the day. Cycle is like off is 30 sec or so, and on is a few minutes.
Thanks,
Milosh
A question bothers me for a while and haven't found an answer for it. Hope community knowledge will step up. :) People are saying that it is not good idea for high rpm motor to be switched on/off very often. Motor I am talking about is used for vacuum holding wood panels during cutting on a cnc machine. Owners rather use valve to turn on/off vacuum while load / unload panels than switch motors on/off.
Is there anything what may damage motor by repeating on/off cycle during the day. Cycle is like off is 30 sec or so, and on is a few minutes.
Thanks,
Milosh





RE: Switching on/off vacuum motors
The answer depends on factors we don't know, starting with "How big is the motor?", and "How is it controlled?".
RE: Switching on/off vacuum motors
Every time an electric motor is started, it generates heat. And components supplying electricity to the motor endure heat as well.
Fuses get hot, circuit breakers get hot, and most of all... the coil windings within the motor get hot.
As the motor runs, it has an opportunity to cool from its initial startup.
If the motor is not given ample time to level off to its designed operating temperature, degradation of the coil winding(s) can begin.
The larger the motor, a longer time between starts is required.
Electric motor duty cycles have been labeled; continuous, intermittent, periodic, short-time, varying, etc.
John
RE: Switching on/off vacuum motors
Depending on the size, the inertia and the load turning a motor momentarily (part of a second to several seconds, it depends) may generate torque and current transients that may damage or break shafts and blow fuses.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Switching on/off vacuum motors
Using a valve that completely shuts off the vacuum motor inlet reduces the load on the motor, typically producing a large increase in motor speed, but also reducing the cooling air flow.
In this case, it's probably a good idea to vent the vacuum motor's inlet during the 'off' portion of the cycle, to provide some cooling air flow through the motor.
Mike Halloran
Pembroke Pines, FL, USA
RE: Switching on/off vacuum motors
What type of vacuum pump is it?
How is the motor cooled?
Is this a vacuum cleaner type of setup?
Universal motors, small AC-DC motors with brushes, do not suffer as much larger induction motors from repeated starts. Universal motors do tend to speed up noticeably when the load is removed, but they are designed to handle the no-load speeds.
Can you give us a make and model of the vacuum pump?
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Switching on/off vacuum motors
Muthu
www.edison.co.in
RE: Switching on/off vacuum motors
It is an AC motor with brushes. It is like one used in a central vacuums. Spec says 8A at 220v and run at 22000 rpm and there is no nameplate. Here is the link where I got it from. Model is Lighthouse LH7123. There is no data regarding the temperature of the core (coils)s well. Is there any rule of the thumb what temperature shouldn't be reached? I understand, cooler the better, but they get hot during normal operation, and it looks like they are designed to be like that. What would be their "normal" working temperature?
Thanks,
Milosh
RE: Switching on/off vacuum motors
"You measure the size of the accomplishment by the obstacles you had to overcome to reach your goals" -- Booker T. Washington