Extending brushed DC motor lifespan in vacuum pump

Thread Starter

Dhaya777

Joined Oct 20, 2014
4
Hi guys,

I have a brushed DC motor vacuum pump that needs to hit a target vacuum and maintain that level with a constant minimal leak. Meaning the vacuum will never be stable. I have 2 options for motor control

1. PID system which keeps the motor running constantly

2. An algorithm that runs the motor to achieve a vacuum +15% above target, stops the motor and comes on again after the vacuum reaches -15% below target vacuum and repeats the process indefinitely.

Which one will lead to longer motor life?
 

nsaspook

Joined Aug 27, 2009
8,906
Normally you would with a constant gas flow-rate let the vaccum pump run constantly and use an auto or manual throttle valve to control the vacuum line conductance out of the chamber to control to a vacuum set-point.
 

Marley

Joined Apr 4, 2016
425
It's a brushed motor. The brushes have a finite life (many thousands of hours - hopefully - but still finite).
I would have the motor doing maximum amount of work while running.
So I would go for the ON-OFF above and below target approach. Could be closer than the ±15% limits though. Also means that the controller is cheaper.
Check the brushes regularly.
 

MaxHeadRoom

Joined Jul 18, 2013
23,932
2. An algorithm that runs the motor to achieve a vacuum +15% above target, stops the motor and comes on again after the vacuum reaches -15% below target vacuum and repeats the process indefinitely.
Which one will lead to longer motor life?
What will the expected or typical duty cycle be?
 
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