What do you mean?
Makings of a generator
- Thread starter TonyM
- Start date
Help Support Home Model Engine Machinist Forum:
Exactly what I said.
Hint would be, coils need to be wound in a given sequence to operate as a generator.
BaronJ
Grumpy Old Git.
Hi Tony,
Depending upon whether the motor is three phase or single phase the diagram I posted is correct. A single phase motor will only have two ends to a winding whilst a three phase one will have the ends of the three windings common, unless there are six wires coming out in which case you will have to sort out which pairs are the start and finishes of each one.
Depending upon whether the motor is three phase or single phase the diagram I posted is correct. A single phase motor will only have two ends to a winding whilst a three phase one will have the ends of the three windings common, unless there are six wires coming out in which case you will have to sort out which pairs are the start and finishes of each one.
The Alternators in a car generator is this circuit. Which maybe a Item you could use.
Thanks Baron I understand. I am still not sure what Bluejets is getting at.
The motor came off a 240V single phase dishwasher. However it is exactly like the diagram in #18. There are three sets of three coils. The three coils in each set are connected in series. The last coil in each set are joined to each other. The first coil in each set are connected to separate terminals. I assume its three phase or single phase depending upon whether one set of coils is connected or all three. For it's original purpose I would guess that one set could be 110V and two sets 220V I have no idea which terminals were originally used. But I would have thought that is irrelevant.
When used as a generator, will the output not vary depending upon the speed. As I said in my first post actual output is not so important. On a model, it would be nice to be able to use it for charging a battery for ignition / mobile and a few diodes. I have all options open to me and it would be nice to find out the best way ( without reconnecting each individual coil) to connect the three sets of coils to give the highest output at relatively low speed of a model engine.
The motor came off a 240V single phase dishwasher. However it is exactly like the diagram in #18. There are three sets of three coils. The three coils in each set are connected in series. The last coil in each set are joined to each other. The first coil in each set are connected to separate terminals. I assume its three phase or single phase depending upon whether one set of coils is connected or all three. For it's original purpose I would guess that one set could be 110V and two sets 220V I have no idea which terminals were originally used. But I would have thought that is irrelevant.
When used as a generator, will the output not vary depending upon the speed. As I said in my first post actual output is not so important. On a model, it would be nice to be able to use it for charging a battery for ignition / mobile and a few diodes. I have all options open to me and it would be nice to find out the best way ( without reconnecting each individual coil) to connect the three sets of coils to give the highest output at relatively low speed of a model engine.
BaronJ
Grumpy Old Git.
Hi Tony,
When I first looked at the diagram on P18 I thought that it was star connected three phase, it didn't occur to me that you are right it would be 110 volts and 220 volts depending upon which wires you chose.
The highest output would be the 220 volt connection, that would also have the highest resistance. Yes the output will vary with speed of rotation.
As an aside I've just had a quick play with a washing machine pump that I've had laying around for a few years. The rotor flicks round as if it already has magnets in the rotor. I counted five definite steps. If I put an AC volt meter across the coil it jumps up to about 80 volts every time I flick it round. so you need to be aware that the voltage output might be more than you expect.
When I first looked at the diagram on P18 I thought that it was star connected three phase, it didn't occur to me that you are right it would be 110 volts and 220 volts depending upon which wires you chose.
The highest output would be the 220 volt connection, that would also have the highest resistance. Yes the output will vary with speed of rotation.
As an aside I've just had a quick play with a washing machine pump that I've had laying around for a few years. The rotor flicks round as if it already has magnets in the rotor. I counted five definite steps. If I put an AC volt meter across the coil it jumps up to about 80 volts every time I flick it round. so you need to be aware that the voltage output might be more than you expect.
Hi Ignator,
Back in the 1970s I did a job where I was using old motor windings to make a solenoid switch... where a gap in the magnetic loop between input and output of a transformer made the output voltage vary ... but that aside, I was re-insulating wiring soldered joints with shellac. The lacquer used for the original winding "enamel" insulation from the old transformer.
Now Shellac is an organic lacquer, that becomes dissolved into a liquid in alcohol... So washing windings in alcohol is NOT a good idea, in case you wash away some insulation and it is then thinner than planned.... so fails at a lower voltage than the designer intended...
I suggest you test (or get a PROPER electrician to test) the insulation resistance of your windings using a 1000V Mega tester. NOT an AVO meter. It is the only (simple) way to be sure the windings will not suddenly blow-up, when HOT and a small voltage spike hits the windings.
Any electricians help me on this? - NOT my trade, just what the proper electrician told me when I was doing a job...
K2
Back in the 1970s I did a job where I was using old motor windings to make a solenoid switch... where a gap in the magnetic loop between input and output of a transformer made the output voltage vary ... but that aside, I was re-insulating wiring soldered joints with shellac. The lacquer used for the original winding "enamel" insulation from the old transformer.
Now Shellac is an organic lacquer, that becomes dissolved into a liquid in alcohol... So washing windings in alcohol is NOT a good idea, in case you wash away some insulation and it is then thinner than planned.... so fails at a lower voltage than the designer intended...
I suggest you test (or get a PROPER electrician to test) the insulation resistance of your windings using a 1000V Mega tester. NOT an AVO meter. It is the only (simple) way to be sure the windings will not suddenly blow-up, when HOT and a small voltage spike hits the windings.
Any electricians help me on this? - NOT my trade, just what the proper electrician told me when I was doing a job...
K2
BaronJ
Grumpy Old Git.
Hi Ken,
Perfectly correct ! I've seen spirit washed windings arc over between turns on a transformer that I used for a 3Kv power supply I built for a high power RF amplifier. A mistake I had to quickly rectify. Strangely enough it produced a sharp clicking sound, which was how I originally discovered it.
I still have my Evershed megger !
Perfectly correct ! I've seen spirit washed windings arc over between turns on a transformer that I used for a 3Kv power supply I built for a high power RF amplifier. A mistake I had to quickly rectify. Strangely enough it produced a sharp clicking sound, which was how I originally discovered it.
I still have my Evershed megger !
- Joined
- Oct 1, 2010
- Messages
- 1,404
- Reaction score
- 431
Baron J,
You said you were playing with a washing machine pump. Could it be that the "...as if it has magnets" is due to magnets used to couple the motor part of the assembly to the pump part of the assembly. That is a common construction technique for fractional-horsepower pumps I have seen and worked with to isolate the electrified parts from the fluid-handling parts.
An example:
https://www.pumpproducts.com/little...MIoOW454y7iQMVXjfUAR3J6RqqEAQYCiABEgLGmvD_BwE
--ShopShoe
You said you were playing with a washing machine pump. Could it be that the "...as if it has magnets" is due to magnets used to couple the motor part of the assembly to the pump part of the assembly. That is a common construction technique for fractional-horsepower pumps I have seen and worked with to isolate the electrified parts from the fluid-handling parts.
An example:
https://www.pumpproducts.com/little...MIoOW454y7iQMVXjfUAR3J6RqqEAQYCiABEgLGmvD_BwE
--ShopShoe
BaronJ
Grumpy Old Git.
Hi ShopShoe,
Its quite possible that the impeller is magnetically coupled to the rotor ! Without actually destroying the totally sealed plastic housing I can't really tell. About the only other information I can offer is that the motor is rated at 230 volts 90 Watts. The fact that I get a voltage pulse when I flick the impeller blade round does suggest that its capable of generating an output voltage. I'll take a picture later and post it.
Its quite possible that the impeller is magnetically coupled to the rotor ! Without actually destroying the totally sealed plastic housing I can't really tell. About the only other information I can offer is that the motor is rated at 230 volts 90 Watts. The fact that I get a voltage pulse when I flick the impeller blade round does suggest that its capable of generating an output voltage. I'll take a picture later and post it.
BaronJ
Grumpy Old Git.
Hi ShopShoe, Guys,
Sorry for being a bit slow with the pictures !
The top picture is the complete pump. Next one is after removing the impeller housing. Then the pump broken down into its components. Actually the field coil just presses off the lamination stack. Next the rotor housing. This part cannot be taken apart without destroying the pump. Last that is a piece of steel that is attracted to the magnets inside that is part of the rotor. If I turn the pump blades that bit of steel follows the rotation.
I did power up the pump and tried to hold the impeller but it simply screwed itself more tightly onto the shaft.
Hope that these pictures help.
Sorry for being a bit slow with the pictures !
The top picture is the complete pump. Next one is after removing the impeller housing. Then the pump broken down into its components. Actually the field coil just presses off the lamination stack. Next the rotor housing. This part cannot be taken apart without destroying the pump. Last that is a piece of steel that is attracted to the magnets inside that is part of the rotor. If I turn the pump blades that bit of steel follows the rotation.
I did power up the pump and tried to hold the impeller but it simply screwed itself more tightly onto the shaft.
Hope that these pictures help.
So I tested the original windings with a magnetic rotor and the best I could measure was 0.5volts @500RPM.
In order to keep the original motor windings intact, I decided to use the dishwasher motor. I made a new barrel to hold the windings and used the old rotor shaft in the Dishwasher Rotor.
Put it all together and ran it at 500RPM (Unmeasured, but stated cordless drill speed) The output between each pair of terminals came out identical at 15.4VAC @ 24Hz. I don't know if that is the correct way or if I should connect a cable to the common end of the coil and measure between that and each phase.
If what I have done so far is correct then I am looking for a bit of advice on which diodes to select in order to rectify as per the drawing in #19. It would be nice to be able to keep the RPM between 500 and 1000 so that it can be driven off a pulley rather than the flywheel. There is room inside the existing bell housing for a set of diodes if they are not too big but I don't mind to put them in the control panel with the AC going to the panel if needs be..
In order to keep the original motor windings intact, I decided to use the dishwasher motor. I made a new barrel to hold the windings and used the old rotor shaft in the Dishwasher Rotor.
Put it all together and ran it at 500RPM (Unmeasured, but stated cordless drill speed) The output between each pair of terminals came out identical at 15.4VAC @ 24Hz. I don't know if that is the correct way or if I should connect a cable to the common end of the coil and measure between that and each phase.
If what I have done so far is correct then I am looking for a bit of advice on which diodes to select in order to rectify as per the drawing in #19. It would be nice to be able to keep the RPM between 500 and 1000 so that it can be driven off a pulley rather than the flywheel. There is room inside the existing bell housing for a set of diodes if they are not too big but I don't mind to put them in the control panel with the AC going to the panel if needs be..
BaronJ
Grumpy Old Git.
Hi Tony,
1N1001/2/3/4/5/6/7
Any of these will do ! They are all rated at 1 amp. The 1N1001 is rated at 100 volts, but the voltage rating gets higher as the last number increases. The 1N1007 is 1000 volts at 1 amp. All these diodes are the same physical size and cost only a penny or two. For what its worth I just salvage mine from scrap equipment. Almost any piece of electronic gear will have at least three or four.
https://www.radwell.co.uk/Buy/DIODES INC/DIODES INC/1N4007-T?msclkid=4bd9a161a77012a9f94fc64e0abbe297&utm_source=bing&utm_medium=cpc&utm_campaign=TO_PMax - UK All Products&utm_term=www.radwell.co.uk&utm_content=General Asset Group&adlclid=4bd9a161a77012a9f94fc64e0abbe297
BaronJ
Grumpy Old Git.
Hi Tony,
Thanks for the video.
Part of the problem with multi-meters is that they are designed for relatively low AC frequencies, 20 to 150 Hz and the readings drop off as the frequency goes up. If you want to capture the voltage at higher frequencies you need to use an oscilloscope.
The rectifiers I mentioned are good up to few hundred Hz.
Thanks for the video.
Part of the problem with multi-meters is that they are designed for relatively low AC frequencies, 20 to 150 Hz and the readings drop off as the frequency goes up. If you want to capture the voltage at higher frequencies you need to use an oscilloscope.
The rectifiers I mentioned are good up to few hundred Hz.
Please advise, would a galvanometer AVO meter give accurate voltages at higher frequencies? I guess it is actually measuring half-wave rectified Rms voltage and scaling as Rms full wave voltage.... so peak voltage - for a diode rating - should be 1.7321 times that reading? 50 V reading needs > 85 V, so select a 100 V diode?
Also, as generators are super sensitive to air gaps, the gaps between rotor and stator should only be a couple of thou? Motors can get away with bigger gaps from what I have seen?
finally, generators are near linear for speed versus voltage, if using a constant magnetic fieled from Permanent magnets.... ( I think?).
K2
K2
Also, as generators are super sensitive to air gaps, the gaps between rotor and stator should only be a couple of thou? Motors can get away with bigger gaps from what I have seen?
finally, generators are near linear for speed versus voltage, if using a constant magnetic fieled from Permanent magnets.... ( I think?).
K2
K2
Last edited:
BaronJ
Grumpy Old Git.
Hi Ken,
The AVO 7 & 8 and its derivatives all use a selenium rectifier, so any AC frequency higher than about 150 Hz will be woefully inaccurate. I don't think that they ever replaced those with silicon diodes.
As far as silicon diode ratings are concerned I've stopped bothering to consider voltage ratings. There seems to be more diodes rated at 1Kv in use than low voltage ones. If you think about it, just looking at the 1N100x range There is essentially no difference in price between the 1N1001 and the1N1007, so why not use the highest rated one !
Yes rotor to stator should have the smallest practical air gap. But the shape of the magnetic field in a commercial motor or generator is carefully controlled to get the sharpest switch off between them consistent with the smoothness of rotation or output.
On a motorcycle, (~1973?) I fitted a different rotor and stator on the end of the crankshaft - changed from 0.004in clearance all around to 0.002in clearance all around. BUT crank-flex needed the larger air gap! (or so I learned the hard way.) After a good run - when the electrics were well cooked by the rubbing of rotor on stator, - I had a 0.003 in gap ... and less magnet than before and no useful windings... = no output. Cost me a rewind of the stator, and back to the old rotor to give 0.004in clearance, and not a lot of output (rated at 60W, but not sure it ever did that!). A later change from a Lucas to Wipac stator solved my power problem. - Just more windings...
K2
K2
I am just a little concerned about your testing... The motor original rating will be a voltage and power rating, - which also relates to the heat/temperature that the motor can withstand. (I.E. inside the windings).
Heat is generated by current, not voltage, so while it is good to note the voltage "open circuit" you need to do some tests with a suitable load (a filament bulb?) and record current as well as voltage.
And you must make sure it does NOT exceed the original motor voltage, as the winding insulation is "not new" and may well be worn or damaged and any excess could flash-over internally - creating a local source of heat that will destroy the motor.
Do not exceed the power rating (voltage x current), and after deducing the original current max continuous rating (Power rating divided by Voltage), make sure you do not exceed the current rating either.
e.g. 90 W at 220V = 0.41A.
0.41A at 100 v = 41W. - so a 41W bulb at 100 V is 100/0.41 = 244 OHMS. I.E. a 0.6W bulb at 12 V, or a 200W bulb at 220V would have the same resistance so can be used to simulate the 100V running condition. Of course a 100W 220V bulb is about twice the resistance (484 Ohms), so about half the current so would be a good current limiter for test purposes. I guess these may be available wherever you shop? - IF you can still get filament bulbs! 2 in parallel should be a good full load at 100V, But NOT for a higher voltage.
Incidentally, 100V can kill if it gets across the heart, so please practice the best electrical safety procedures when wiring-up and running these things. I only takes 1 shock to stop the heart. - We want you to avoid that and finish this interesting post.
I hope I am not too far from the "electrical truth" as I am a humble "mechanical" man... Bits of moving metal are easier to comprehend in my brain than "invisible" electrons and Electromagnetic "fields" - and heat, volts, thermodynamics, women, and all the other mystical things in the universe, etc...
K2
Heat is generated by current, not voltage, so while it is good to note the voltage "open circuit" you need to do some tests with a suitable load (a filament bulb?) and record current as well as voltage.
And you must make sure it does NOT exceed the original motor voltage, as the winding insulation is "not new" and may well be worn or damaged and any excess could flash-over internally - creating a local source of heat that will destroy the motor.
Do not exceed the power rating (voltage x current), and after deducing the original current max continuous rating (Power rating divided by Voltage), make sure you do not exceed the current rating either.
e.g. 90 W at 220V = 0.41A.
0.41A at 100 v = 41W. - so a 41W bulb at 100 V is 100/0.41 = 244 OHMS. I.E. a 0.6W bulb at 12 V, or a 200W bulb at 220V would have the same resistance so can be used to simulate the 100V running condition. Of course a 100W 220V bulb is about twice the resistance (484 Ohms), so about half the current so would be a good current limiter for test purposes. I guess these may be available wherever you shop? - IF you can still get filament bulbs! 2 in parallel should be a good full load at 100V, But NOT for a higher voltage.
Incidentally, 100V can kill if it gets across the heart, so please practice the best electrical safety procedures when wiring-up and running these things. I only takes 1 shock to stop the heart. - We want you to avoid that and finish this interesting post.
I hope I am not too far from the "electrical truth" as I am a humble "mechanical" man... Bits of moving metal are easier to comprehend in my brain than "invisible" electrons and Electromagnetic "fields" - and heat, volts, thermodynamics, women, and all the other mystical things in the universe, etc...
K2
Similar threads
