Makings of a generator

[TonyM]

Hi All.
To put things into perspective. I didn't "set out" to make a generator. I just found these old motors and thought they would look like a nice scale generator to pair with some engines. There are a few small scale generator sets and kits available but not "medium" sized as I would class these. I saw a few ways to convert them to generators using permanent magnets and so set on this journey to see what, if anything, was possible. I tried the original windings with the PM rotor and that provided low out put. Then I tried with the dishwasher internals inside the old frame. Which is where I am still with no real usable output.
It was really a case of trying to make something that worked out of bits and pieces.
I have very little knowledge of generators and motors and have learned quite a bit so far so all is not wasted. What I have learned is that induction motors make poor generators without high RPM and/or excitation. Permanent magnet motors easily generate electricity but not necessarily useful power. The windings are fairly critical so "any old motor" won't necessarily be able to generate useful power. Maybe that's what Bluejets was alluding to in his post.

What I was hoping for Ken, was something that could perhaps charge a small battery that in turn would supply power for a couple of diodes plus the engine ignition. I imagine that is quite feasible if one used say a small starter generator from a lawnmower or similar, but unlikely from ad hoc 240volt motor similar to the one I was trying to use. Unless there is another way like re-connecting the 9 coils differently.

 

[BaronJ]

Hi Tony, Guys,

Putting the windings in series will increase the voltage but not necessarily the current available.

Tesla played about for quite a while whilst coming up with electric power generation.
He standardised on 60 Hz when using Niagara Falls to generate power for north America. Most of the rest of the world uses 50 Hz.

I've one or two Ideas for a usable generator ! Small cheap toy electric motors will generate several volts at a few milliamp. Using a stepper motor is another if the driver has enough power. I'm tempted to have a play with some devices that I have kicking around.

 

[Rdean33422]

I don't know if this is helpful but this is a stepper motor driven by my V Twin I did a few years back.



Ray

 

[BaronJ]

Hi Ray,

Thank you for your post & video.

That is the sort of output, approximately 100 volts, I would expect from a stepper motor used as a generator. What is the bulb wattage ?

There are a lot of stepper motors used in printers, scanners and the like !

 

[Steamchick]

Hi Tony,
I hope I have been able to give you a better understanding of what you need...
Some "simple rules"?

• Windings - wire size and length - determine the CURRENT for a motor of generator. A 240V 1 A motor is only good (safe) at 1 A at whatever voltage.
• Speed of pole piece passing a coil generates voltage. e.g. a 500rpm 1 " dia rotor develops 1/3rd of the voltage of the same coil and magnet as a 3" rotor. - which is why "modern" generators tend to be shorter shaft and larger diameter shaped than the earliest designs of dynamos.
• Simply connecting coils in series to develop more power... - wrong - just more volts. 3 phases at 12V and 1A = 3 x 12W = 36 W. Connect coils in series = 1 set at 3 x 12V = 36V x 1A = 36 W. But maybe more volts is more useful? 3 x 4V = 12V for an ignition system?
• More speed is more power - YES! Gear it up to run it faster. = More load on the engine though, so understand the engine's "sweet-spot" where it produces best torque, then decide gearing (belt pulley sizes?) to get the generator at the speed it needs to run at for the power you need..
• For an ignition system, I figure current is important, as many systems are for low voltage DC - from batteries. So when you have generated more than 12V, connect sets of coils in parallel (which is what the diodes are doing on the 3 phase motor conversion) so at 12V (to power ignition) you get max current. 3 x 1A sets of windings in parallel = 3A... But connect sets of windings via a diode bridge, as you have done with the 3-phase motor - so the 12V DC output is connected in parallel. If your 3 phase motor is pumping-out 60V x 1A with each phase being 3 coils, then re-connect coils in parallel (per phase) so you get 20V and 3A across the diodes per phase. Then a cheap 12~24V DC to 12V DC "buck controller" (1 per phase) can handle the voltage conversion from the generator to charge a 12V battery.
• I do think you need to understand Amps are as important as Volts. So High voltage and milliamps is "not useful", as is very low voltage!. But what Voltage and Current does your proposed ignition need?

Hope this helps,
K2