Makings of a generator

TonyM · Oct 18, 2024

Just picked these fractional HP motors up at a local market for a few pounds. I think they will make nice period scale generators. One shown next to the Gardner for an idea of size. They are about 3.5"/90mm Dia x 3.5"/90 long. They were made locally in the '50's '60's

GreenTwin · Oct 18, 2024

Looks nice, what sort of specs on the generators/alternators ?

.

TonyM · Oct 18, 2024

GreenTwin said:
Looks nice, what sort of specs on the generators/alternators ?

.

I will have to strip them down and check out the windings to see what can be done. Worst case they will just drive some diodes but would like to have at least 12V. I just bought them because they were nice frames and a handy size. At less than a fiver each they were too good to leave.

peterl95124 · Oct 19, 2024

if they are AC induction motors they can't be used as is, but you might be able to replace the rotor with a custom made one containing magnets

TonyM · Oct 20, 2024

peterl95124 said:
if they are AC induction motors they can't be used as is, but you might be able to replace the rotor with a custom made one containing magnets

They are induction and that's exactly what I intend to do.

Toymaker · Oct 20, 2024

The small motors used on drones make excellent alternators without any modification. These motors are brushless outrunners and put out 3 phase AC when used as a generator. A few diodes, or an automotive alternator rectifier pack, will convert the 3 phase AC into DC.

BaronJ · Oct 20, 2024

TonyM said:
I will have to strip them down and check out the windings to see what can be done. Worst case they will just drive some diodes but would like to have at least 12V. I just bought them because they were nice frames and a handy size. At less than a fiver each they were too good to leave.

Hi Tony,

You could try adding magnets to the rotor !
Drill suitable depressions, and super glue magnets in them.

TSutrina · Oct 20, 2024

I am a mechanical engineer that know a single phase motor can be turned to a generator so did some searching. https://en.wikipedia.org/wiki/Induction_generator

If you want to get deep into the weeds try this https://www.researchgate.net/public...erating_as_a_self-excited_induction_generator

https://www.techscience.com/iasc/v28n3/42258/pdf

https://ieeexplore.ieee.org/document/790909

TonyM · Oct 22, 2024

I guess most of us have a "That might come in handy" box as I do. I found this dishwasher pump that I had thrown in and it looks like it will be a good fit to replace the internals of the old motor. A slow turn showed voltage on the multimeter.

ignator · Oct 22, 2024

TonyM said:
I guess most of us have a "That might come in handy" box as I do. I found this dishwasher pump that I had thrown in and it looks like it will be a good fit to replace the internals of the old motor. A slow turn showed voltage on the multimeter.

WHY? That old motor looks so cool (the guts, but not the existing bell housings). Have you found that field winding of the stator to be shorted or grounded? Insulation on these old motors last, if they were not left in total uncontrolled moister conditions. If you made antique looking bell housings with large openings, that could display the windings, that you can paint new insulation red-oxide enamel Glyptol is a trade mark name in the USA of such a product. It's universal to painting on motor windings, I've seen it in spray cans. But I would first use a tooth brush and dish soap and water to clean the motor coils up. They may be fine with the aged patina and you can see if there's cracked insulation.
That new motor hidden inside the old motor, still needs to be converted to a generator.
I know nothing about how to do that, or if just putting permanent magnets on a new rotor or your intended machining grooves in the existing rotor will produce enough flux to produce the desired voltage output, but I assume it's a 220-240VAC motor, and that should work.

Looks like you tried to arc the slots closed where the induction motor shorting bars were?
That silicon steel of the rotor with stick rod filler, what Rockwell hardness did that produce? Still looks like the right way to go for antique coolness factor without stick building everything from scratch. But to mill hard steel, needs ceramic end mills, coolant, and a rigid milling machine. You could build a new rotor, with as many even count slots you can machine in that diameter and magnet size you want to fit in.
Your motor looks marvelous!

TonyM · Oct 22, 2024

All I know is that these are 40, 10watt, and 16 watt 240/110 This is the first one I opened up. What you see that looks like welding is but it is copper and is on both ends of the rotor with lots of shellac. I have just checked the windings of all three and there are non shorted to the frames.
The 10w has two red and two black wires. The resistance for each pair is 45 Ohms. The 40watt also has two red and two black wires. Each pair measures 21 Ohms. When measured across the two black reminals I get 42 Ohms. Nothing between the two red. Not sure what is happening here. The 16W has three wires, red black and brown Red to Black is 120 Ohms, Black to Brown is 113 Ohms and Red to Brown is 233 Ohms.

TSutrina · Oct 22, 2024

TSutrina said:
I am a mechanical engineer that know a single phase motor can be turned to a generator so did some searching. https://en.wikipedia.org/wiki/Induction_generator

If you want to get deep into the weeds try this https://www.researchgate.net/public...erating_as_a_self-excited_induction_generator

https://www.techscience.com/iasc/v28n3/42258/pdf

https://ieeexplore.ieee.org/document/790909

Just crunching through the number on the first site. Not believing the power factor that I back calculated. Need a measured current at load. Not the motor must be run above synchronous by about the same speed as difference for the motor.
10 W 110 VAC .7 Amp AC 50Hz
1350 rev/min 10W/110V/0.7A = power factor 0.13
Active power 10W * 0.13 = 1.3W
reactive power sqr(10^2 -1.3^2) = 9.915W
Capacitive current Ic = 9.915W/110V = 0.09 amp
Capacitive reactance Xc = 110V/0.09A = 1222 ohms
Minimum capacitance C = 2*pi*50Hz*1222ohm = 383900 microF

16 W 110 vac 0.9 Amp AC 50hz
1300 rev/min 16W/110V/0.9A = power factor 0.16
Active power 16W * 0.16 = 2.56W
reactive power sqr(16^2-2.56^2)= 15.79W
Capacitive current Ic = 15.79W/110V = 0.1435 amp
Capacitive reactance Xc = 110V/0.1435A = 766.5 ohms
Minimum capacitance C = 2*pi*50Hz*766.5ohm = 240803 microF

40 W 220 vac 0.41 amp AC 50hz
2740 rev/min 40W/220/0.41A = power factor 0.44
Active power 40W * 0.44 = 17.6W
reactive power sqr(40^2-17.6^2) = 35.92W
Capacitive current Ic = 35.92W/220V = 0.163 amp
Capacitive reactance Xc = 220V/0.163A = 13459.7 ohms
Minimum capacitance C = 2*pi*50Hz*13459.7 ohm = 4228489.5 microF

TonyM · Oct 24, 2024

Thanks for the info TSutrina.
I understand that it is necessary to turn the rotor faster than synchronous speed as well as using capacitors before an induction motor can be made to generate. Even then self excitation is unreliable and the voltage generated can vary wildly with small RPM changes. For those reasons I decided it is not practical to try and use it "as is" for low speed model engines. Hence the reason to either add magnets to the existing rotor or to replace the complete internals.

T.S. True sportsman · Oct 24, 2024

ignator said:
WHY? That old motor looks so cool (the guts, but not the existing bell housings). Have you found that field winding of the stator to be shorted or grounded? Insulation on these old motors last, if they were not left in total uncontrolled moister conditions. If you made antique looking bell housings with large openings, that could display the windings, that you can paint new insulation red-oxide enamel Glyptol is a trade mark name in the USA of such a product. It's universal to painting on motor windings, I've seen it in spray cans. But I would first use a tooth brush and dish soap and water to clean the motor coils up. They may be fine with the aged patina and you can see if there's cracked insulation.
That new motor hidden inside the old motor, still needs to be converted to a generator.
I know nothing about how to do that, or if just putting permanent magnets on a new rotor or your intended machining grooves in the existing rotor will produce enough flux to produce the desired voltage output, but I assume it's a 220-240VAC motor, and that should work.

Looks like you tried to arc the slots closed where the induction motor shorting bars were?
That silicon steel of the rotor with stick rod filler, what Rockwell hardness did that produce? Still looks like the right way to go for antique coolness factor without stick building everything from scratch. But to mill hard steel, needs ceramic end mills, coolant, and a rigid milling machine. You could build a new rotor, with as many even count slots you can machine in that diameter and magnet size you want to fit in.
Your motor looks marvelous!

i have a 1937 3/4 hp motor on my 1936 B&S tool and cutter grinder the bearings are immaculate and so is the insides of this sealed motor

ignator · Oct 24, 2024

T.S. True sportsman said:
i have a 1937 3/4 hp motor on my 1936 B&S tool and cutter grinder the bearings are immaculate and so is the insides of this sealed motor

I have a 1930 Rockford #2 horizontal milling machine, with a B&S#9 spindle nose. It was originally overhead belt driven. It was converted with a Lima 4 speed transmission and a 2HP motor of the late 1930s era.
It's a three phase, and I use a VFD to run the motor. I never push it hard, but the original insulation I washed with alcohol to clean all the many years of munge. I cleaned the bearings of the motor, regreased, and this old stuff just works.
I know there's the worry of insulation break down with a VFD/VSD powering it, but the new electronics control the rise and fall time of the pulses to minimize the inductive voltage spikes (older models have very fast edge rates that generate large voltage spikes), I've never had a motor fail in the shop as I've converted all my machines from single to 3ph motors to control spindle speed. I say this as non of the motors are inverter rated.

HMEL · Oct 24, 2024

TonyM said:
All I know is that these are 40, 10watt, and 16 watt 240/110 This is the first one I opened up. What you see that looks like welding is but it is copper and is on both ends of the rotor with lots of shellac. I have just checked the windings of all three and there are non shorted to the frames.
The 10w has two red and two black wires. The resistance for each pair is 45 Ohms. The 40watt also has two red and two black wires. Each pair measures 21 Ohms. When measured across the two black reminals I get 42 Ohms. Nothing between the two red. Not sure what is happening here. The 16W has three wires, red black and brown Red to Black is 120 Ohms, Black to Brown is 113 Ohms and Red to Brown is 233 Ohms.

You might consider trying to locate the winding diagrams if possible. Would give you a head start. Ac motors require a method of starting in singe phase operation which can be either start windings or capacitors. You would get better performance if the windings were working together. A rotor with magnets would most likely give you an alternator but that is easily solved with off the shelf rectifiers. But until you know how the windings are wound its sort of a guessing game what you get. Keep posting its an interesting subject.

TSutrina · Oct 25, 2024

TonyM said:
Thanks for the info TSutrina.
I understand that it is necessary to turn the rotor faster than synchronous speed as well as using capacitors before an induction motor can be made to generate. Even then self excitation is unreliable and the voltage generated can vary wildly with small RPM changes. For those reasons I decided it is not practical to try and use it "as is" for low speed model engines. Hence the reason to either add magnets to the existing rotor or to replace the complete internals.

Not totally surprised. The major use of induction motors that I read about decades ago was it rural India and connected to the grid.

TonyM · Oct 28, 2024

The dishwasher pump motor was 240V AC and it looks like it will generate 3 phase AC. (I could be wrong here) How would the diodes be wired to give 1 phase DC. Controlling the output voltage is less imporant as that is 'off the shelf' stuff. Just not sure what to use to rectify the output. The rotor has six magnets.

BaronJ · Oct 30, 2024

TonyM said:
The dishwasher pump motor was 240V AC and it looks like it will generate 3 phase AC. (I could be wrong here) How would the diodes be wired to give 1 phase DC. Controlling the output voltage is less imporant as that is 'off the shelf' stuff. Just not sure what to use to rectify the output. The rotor has six magnets.

Hi Tony,

Just stick a diode in each output lead, and connect the cathodes together you will then get a DC output between the diode cathodes and the other end of the winding.

bluejets · Oct 30, 2024

BaronJ said:
Hi Tony,

Just stick a diode in each output lead, and connect the cathodes together you will then get a DC output between the diode cathodes and the other end of the winding.

Think you need to take a good look at the way the coils are shown as being wound in #18 above.

Makings of a generator

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