DC CDI

[Fast n Furious]

I agree about the 9v issue with an HID, I have had bad battery connections on mine where the light went out completely at tickover. Doesn't need many revs for it to work though but would be better not to have to rely on the battery. Interesting about the CDI current consumption, I have only noted the current drawn through a car ignition (non CDI) which is around 5 amps with the ignition off

Ignition off?

[coaster]

Sorry, ignition ON but engine not running It was a long time ago though (on my Marcos)and I was investigating a blown 5 amp fuse at the time but thinking about it there were probably other issues involved. Got me thinking now, I'll have to get my meter out at the weekend and check

[Steve J]

Before anyone gets too excited about the merits of 3 phase power, the fact is that the Lambretta 4 pole and 6 pole flywheel magnetos are only single phase devices, and there's no way that playing around with different arrangements of coils on the existing pole pieces is going to change that. To get three phases requires a very different method of construction of the stator plate and windings, so that three AC outputs are continuously produced within three separate windings, with a time shift between the three output waveforms. Having four or six magnets rotating around stators with corresponding four or six equally spaced pole pieces will produce AC voltages in the coils wound onto the pole pieces, and all the voltage waveforms will rise and fall simultaneously - i.e. there is no phase difference between any of them, so only a single phase output is possible, regardless of how the windings are connected. Have a look at the construction of a 3 phase stator for a motorcycle or the stator winding in an automotive alternator, and you'll see the windings are wound continuously around the stator, with the three phase windings wound around different sets of stator pole pieces in sequence. As the magnets sweep past the pole pieces, they will induce the AC voltages in the three sets of windings at different times, creating three separate voltage waveforms shifted equally in time from each other.

[dickie]

Before anyone gets too excited about the merits of 3 phase power, the fact is that the Lambretta 4 pole and 6 pole flywheel magnetos are only single phase devices, and there's no way that playing around with different arrangements of coils on the existing pole pieces is going to change that. To get three phases requires a very different method of construction of the stator plate and windings, so that three AC outputs are continuously produced within three separate windings, with a time shift between the three output waveforms. Having four or six magnets rotating around stators with corresponding four or six equally spaced pole pieces will produce AC voltages in the coils wound onto the pole pieces, and all the voltage waveforms will rise and fall simultaneously - i.e. there is no phase difference between any of them, so only a single phase output is possible, regardless of how the windings are connected. Have a look at the construction of a 3 phase stator for a motorcycle or the stator winding in an automotive alternator, and you'll see the windings are wound continuously around the stator, with the three phase windings wound around different sets of stator pole pieces in sequence. As the magnets sweep past the pole pieces, they will induce the AC voltages in the three sets of windings at different times, creating three separate voltage waveforms shifted equally in time from each other.

Oh bugger

[coaster]

Before anyone gets too excited about the merits of 3 phase power, the fact is that the Lambretta 4 pole and 6 pole flywheel magnetos are only single phase devices, and there's no way that playing around with different arrangements of coils on the existing pole pieces is going to change that. To get three phases requires a very different method of construction of the stator plate and windings, so that three AC outputs are continuously produced within three separate windings, with a time shift between the three output waveforms. Having four or six magnets rotating around stators with corresponding four or six equally spaced pole pieces will produce AC voltages in the coils wound onto the pole pieces, and all the voltage waveforms will rise and fall simultaneously - i.e. there is no phase difference between any of them, so only a single phase output is possible, regardless of how the windings are connected. Have a look at the construction of a 3 phase stator for a motorcycle or the stator winding in an automotive alternator, and you'll see the windings are wound continuously around the stator, with the three phase windings wound around different sets of stator pole pieces in sequence. As the magnets sweep past the pole pieces, they will induce the AC voltages in the three sets of windings at different times, creating three separate voltage waveforms shifted equally in time from each other.

Hear what you say but iff lighting coils are added in place of the LT coil and pickup, why can't they be wired as pairs? that would surely give you the required phase shift wouldn't it ....3 phase theory still gives be nightmares 40 years on

[dickie]

I reckon Steve j is correct. The magnets need to be deliberately arranged so that the voltage from each coil is 120 degrees apart. They might be but if they are it's pure luck.

I was being pretty stupid really. Simply having three voltages that aren't correctly phased is what i was about to do.

That doesn't mean others are being stupid but I'm a chartered electrical engineer so I really shouldn't be such a nob.

[coaster]

I reckon Steve j is correct. The magnets need to be deliberately arranged so that the voltage from each coil is 120 degrees apart. They might be but if they are it's pure luck.

Not giving up just yet lol, those magnets must be spaced to coincide with the 5 coils/poles already in place so surely the 6th pole currently used for mounting the pick up would allow too .....probably right though but we can dream

[dickie]

Yes, you could use it to generate power but we need to generate three sinusoidal (ish) waveforms of the same amplitude and frequency that are equally phase shifted by 120 degrees. Easy if you design it like that but not so easy just by chucking a coil on the laminates and hooking some wires up.

The problem is that we have 6 equally spaced poles and 6 equally spaced magnets. So all three pair of poles will produce the same thing at the same time. Meaning that they will either cancel each other out, add together in one mahoosive waveform, depending on how we connect them.

Thinking out loud, we could still produce a generator with 3 pairs of poles that would give us 50% more charging power but still single phase. Nah, that's bs too unless we go back to 6v.

[Steve J]

[quote="dickie"

That doesn't mean others are being stupid but I'm a chartered electrical engineer so I really shouldn't be such a nob. [/quote]

Don't worry, it's been a long time since I studied electrical engineering, & I reckon I've forgotten most of it!

My claim to fame is that I once got a shock from two mains phases & neutral - I don't know about three phase rotating field theory, it rotated my head for the rest of the day....

[MickYork]

Going back to my original post...

I've been in touch with Anthony Tambs and he has a DC CDI on his scooter. It's early days but it looks as though he will be selling them in the near future. I've ordered one