There was a great discussion back a few months ago on building a regulator for a dynamo. I have a similar challenge except the vintage motorcycle I'm restoring is a racing machine - neither lights not a battery (and no place for them). To the best of my knowledge there are no regulators made to control a dynamo without a battery with specs that match this dynamo.
This non-permanent magnet dynamo is inside an East German MZ motor. It's a 6 V, 60 W Bosch type unit with a D+, DF, and D- connections. The dynamo has an integrated ignition system (points and condenser) driven by a cam on the armature shaft.
This motor is normally used in a motorcycle with lights + battery and the regulator would switch the field coil (resistance of 1.7 Ω) on an off with a Field Winding Resistor (4.1 Ω) bridging D+ and DF.
Since I only need ignition energy the dynamo won't have to do much work. The standard ignition coil's primary is 3 Ω (I also have a high output ignition coil at 1.6 Ω that I'd like to use to get a more intense spark).
If I stick with 6 V (which the ignition coils are designed for), and considering dwell time, powering the standard ignition coil would require a current of around 1.5 A. That will change based on motor speed, but from the experience of others running this motor the variation is about 0.2 A, so 1.3 A at higher speeds.
Here what I'd like to accomplish:
- Voltage: 6 V output
- Amperage: produce a stable 1.3 A to 1.5 A (or 2.8 A to 3.0 A for the high-output ignition coil)
- Efficiency: generate as little heat as possible from the regulator
- Size: approximately 50mm x 50mm x 25mm (I'd like to make a custom aluminum box and pot the final circuit given the vibration environment)
I am not certain how much current, if any, is needed to sustain the field in this dynamo.
I've been told this can't be done with this dynamo, but no one has explained why. I can understand why no commercially available solid state regulators would work since this is a one-off motor. I also have an existence proof - the motorcycle was raced with great success. Unfortunately, all of the electrical wiring was lost so I have nothing to go by... literally re-inventing the wheel.
My thanks for your advice on this one!