A universal motor supposed to be run in two speed stages: full speed / reduced speed and motor will run on intermittent duty like 3 seconds ON / 3 seconds OFF.
So simply I added a serial diode (BY255) to universal motor to run the motor in reduced speed; but one brush wears out faster when other wears out very slow, why?
I suspected from switching transients but surge supressors like NTCs are not a good idea since they need cooling time, and the costs are important if you will talk about PCB circuits which has at least 3-4 components.
- Source: 220 V 50 Hz
- I measure 120 V on motor (rectifed True RMS value)
- BY255: Medium Current Plastic Rectifier (Voltage – 200 to 1300 volt, Current – 3.0 amperes)
- Brushes wears out fine & equal when on full speed intermittent duty
- When i change the direction of diode, then other brush starts to wear out faster. Diodes' anode sided carbon brush wears out faster (the brush electrons flowing into, conventioal current flowing out)
- Motor's contionous work values are 0.45 A, 83 W, 6300 RPM with light but right load.
Edit: I tried another motor with another type brush but continous duty; results are same: one brush (anode side) wears out very fast while the other brush wears out very slow.