stinkwheel
Bovine Proctologist
Joined: 12 Jul 2004
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 Posted: 23:47 - 29 Mar 2005  Post subject: Regulator rectifiers |
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Someone asked me about how these work. I got a bit carried away with my reply so I thought I would post it. I got a bit technical, all you really need to know is that it is a black-box you plug in to your wiring.
In the spirit of furthering understanding however:
| Quote: |
1, What does a rectifier unit actually do? How does it work? |
The alternator on your bike produces electricity by having a magnet spin round a series of three coils very fast.
Each of these coils produces electricity but it is an alternating current (AC), the electrics on your bike work on direct current (DC) in order for there to be a battery. AC batteries are possible but they are very big and cumbersome.
If you were taking the output from one of these coils, the current alternates one way then the other. A diode is an electrical componant made of crystals that only allow electricity to pass through them in one direction. Passing AC through a diode 'chops off' the current that is going in the 'wrong' direction. This would be called 'half rectified' as there are gaps in the supply of electricity where it would have been going in the wrong direction.
This is compensated for by having three coils with three diodes, all of which are sightly out of phase with one another. These phases overlap to give a more constant current. There are still peaks and troughs but these are 'chopped off' by the voltage regulator which is usually incorporated in with the rectifier.
Sounds complicated, better shown as a picture (below).
So in short, a rectifier is three diodes connected in a heat sink to disperse the heat generated by 'chopping off' half the power the alternator generates.
https://www.bikechatforums.com/files/rectifier.jpg
| Quote: | 2, What voltage should it produce? |
Most bikes have an output that varies betwen 12 and 14.5 volts depending on the rev speed but this is determined by the voltage regulator part of the reg/rec unit.
The voltage regulator is another type of diode called a 'zenna diode' which only allows electricity below a certain voltage to pass through it. Any excess is conducted to earth.
| Quote: | 3, Are they made specific for certain bikes or are they universal? |
Early bikes used to have these componants seperatley, so three diodes and a zenna diode bolted to the frame somewhere. A little later they made the rectifier as a seperate unit set in resin but still had a seperate zenna diode bolted to the frame. Later still they made the whole lot in the same unit.
The answer to your question is that some are, some aren't. Most Japanese bikes have magnets in the alternator and three charging phases. These are technically interchangeable providing your bike runs on the same voltage (12v or 6v). These are by far the most common.
BUT
Some bikes have only two phases.
Some bikes have no magnets in the alternator and use electromagnets instead, these need a special type of regulator that controls the voltage output by varying the power supplied to the electromagnets (be carefull with these, a dodgy one can put out enough current to do you some serious damage)
Some smaller bikes just use the raw AC electricity for the headlights (like the honda H100) and DC for the flashers and taillight, they only charge the battery using a single, half rectified phase and use the battery to damp out the fluctuations in voltage.
Sorry if I have gone into too much detail
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“Rule one: Always stick around for one more drink. That's when things happen. That's when you find out everything you want to know.”
I did the 2010 Round Britain Rally on my 350 Bullet. 89 landmarks, 3 months, 9,500 miles. |
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Big Pete
Spanner Monkey
Joined: 18 Jul 2004
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