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Author
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Topic: New Carbon Brushes for GS1200 Take up Motor
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Steve Klare
Film Guy
Posts: 7016
From: Long Island, NY, USA
Registered: Jun 2003
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posted July 24, 2018 10:37 AM
A DC electric motor is a set of electromagnets on a shaft inside a permanent magnet held in place. When current flows in the coils of the rotor, a magnetic field is established that the permanent magnets attract (and/or repel). This turns the rotor until the magnetic fields align.
Here it could stop, so to keep going, the next set of coils at the right spot need to be energized and the first set turned off: this is good for another fraction of a turn.
This means somehow you need to keep applying power to the rotor and turning it on and off to the right coils at exactly the correct angle of rotation. (-kind of like all those cylinders in a car engine firing at the right time to keep it turning.)
So you have a set of copper contacts on the rotor wired to the coils and two stationary brushes sliding on them. The operating voltage is applied to the brushes Everything is set up at the correct angles to make it work correctly. This acts like a very sophisticated synchronized switching system, but it's just angles and wiring.
-These days they'd be writing and debugging code for weeks!
Being that the brushes slide, there is friction, so there is wear. They are softer than the copper, so they wear to the right shape to make good contact (less arcing). They are much easier to replace than the copper commutator, so they have their service life and then get replaced by the next set (-for the greater good!).
It's a wonderful, simple idea that changed the World.
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All I ask is a wide screen and a projector to light her by...
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