Author Topic: Induction Motor Generators  (Read 667 times)

glort

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Induction Motor Generators
« on: June 28, 2018, 11:45:05 AM »

In the process of setting up my IMAG again.  Might have it running tomorrow.
Been a few years since I touched it  so I have forgotten more than I remember about them.

Anyone else set one up and put it to any practical use?

Anyone know of any off the shelf controllers for them or schematic to build a controller?

EdDee

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Re: Induction Motor Generators
« Reply #1 on: June 29, 2018, 09:32:38 AM »
Hey Glort...

Use one regularly.... As a mains "booster".... No controller, no frills, no dangly bits, just hook it up and slow the meter down by turning up the wick on the pump....

Cheers
Ed
12/1 750RPM/9HP Roid 5kVA- WMO Disposal/Electricity & Hot Water Gen
12/1 650RPM/8HP Roid 4.5kVa - Demon Dino
Chinese Yanmar - Silent Runner with AutoStart
Classic Komatsu 1963 Dozer/Fergusson 35 Gold Belly ...
Bikes,Cars,Gunsmithing & Paintball...Oh yes, a 5Ha open air Workshop to play in!

glort

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Re: Induction Motor Generators
« Reply #2 on: June 29, 2018, 02:29:08 PM »

Hey Ed,

Thinking of doing the same. What size motor you have and what sort of power you get out of it?

Apwnt a very frustrating afternoon trying to get this and some other things together.  I have thrown out too much of the stuff I should have kept and kept what I should have thrown out.  I can see I'm going to have to revise my build strategy. Get all the bits together first instead of presuming I have them then getting frustrated when I realise I don't.

Hardware is too far away to be running down there every 5 Min and they didn't have what I wanted anyway. Thankfully I looked it up on line before I went. spose I have got that bit smarter.

EdDee

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Re: Induction Motor Generators
« Reply #3 on: June 29, 2018, 04:12:03 PM »
Hey Glort...

I am using an enormous 3 phase motor.... About 200Kg worth(Using one phase in delta I think...).... Cant remember what its rating is though, its in the bottom of the chassis on TM2 belted to and below the Genhead proper... I just move from Island to Assist by switching the plugs... TM2 puts out around 8 horsies or so, I haven't run him to coal on it yet, my output is used to slow the meter, but cant do a reverse on it as it is an electronic, oh no you don't, one!

I have made up my mind to die on this property.... NO WAY am I going to try and move! I am managing to use up my extraneous bits lying around though.....

Cheers
Ed
12/1 750RPM/9HP Roid 5kVA- WMO Disposal/Electricity & Hot Water Gen
12/1 650RPM/8HP Roid 4.5kVa - Demon Dino
Chinese Yanmar - Silent Runner with AutoStart
Classic Komatsu 1963 Dozer/Fergusson 35 Gold Belly ...
Bikes,Cars,Gunsmithing & Paintball...Oh yes, a 5Ha open air Workshop to play in!

glort

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Re: Induction Motor Generators
« Reply #4 on: June 29, 2018, 06:13:36 PM »

There is a 3 phase 20 Hp going pretty cheap not too far away from me. Been umming and ahhing about it. Only thing is it's a 2 Pole 2950 RPM which means I have to spin the thing pretty fast.
I have a 12 Hp Ruggerini that would turn it. Beast of a thing though. seems to snap every bolt I try to hold it down with.

Hard enough moving the 4Kw motor and 6 hp China engines around. Spose I could put that engine crane to work though.
Should give me an easy 5Kw though. Although would that be over 3 Phases or 1?

I forget more of this stuff than I remember!

old seagull man

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Re: Induction Motor Generators
« Reply #5 on: August 15, 2018, 12:23:53 PM »
This is some info i looked at a while back, on using a 3 phase motor as a gen, it might help some with the basics.


https://www.pakwheels.com/forums/t/3-phase-motor-generator-conversion/196032

glort

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Re: Induction Motor Generators
« Reply #6 on: August 15, 2018, 12:48:20 PM »

I have to disagree with the recommendation of 7.5 Uf caps for a 4 KW motor.  they will work but you will have to spin the motor faster to make power which will put the frequency off.  Spose OK for resistive loads but I like to keep engine speeds down anyway so I find the 20 Uf caps I use on 5Kw motors are a good match.

Still looking for a big motor.  I bought a 30 HP Ruggerini engine so I have enough engine power to drive anything practical now.

EdDee

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Re: Induction Motor Generators
« Reply #7 on: August 15, 2018, 02:39:01 PM »
Hi Guys....

A word of experience, forget trying to run an induction motor as a prime mover on a dynamic load such as a house etc.... Induction motors as gennies work very well under an even load, where caps can be set up to match the load and one doesn't overload the output to cause flux breakdown and in tandem, loss of output....

Where an induction motor really shines, is when you hook it to an existing prime mover type source, where the excitation voltage comes from the lines that you will be generating onto. All that is needed is a small amount of "overspeed" on the induction motor, now generator, to get things happening... Anything from 2% overspeed to around 10% will give you plenty of power back up the lines...

Glort, I don't know whether you have tried this yet, give it a go if you haven't, you will be surprised at how easy it works. Stick an ammeter on the line, power up the electric motor from a plug point (have the decompressor engaged) and with a bit of help from a crank, the electric motor will spin the engine over.... drop the decompressor and see what happens... The current on the ammeter drops to zero or near zero, if your pulley ratios are right, and the engine is running close to "mains frequency" ... wind up the governor a bit, and the ammeter starts registering the current now flowing BACK down the lines as the induction motor now acts as an induction generator (watch your turny meter for proof) .... Wind it up too much and the flux breaks down and it stops generating....

Have fun....

Cheers
Ed
12/1 750RPM/9HP Roid 5kVA- WMO Disposal/Electricity & Hot Water Gen
12/1 650RPM/8HP Roid 4.5kVa - Demon Dino
Chinese Yanmar - Silent Runner with AutoStart
Classic Komatsu 1963 Dozer/Fergusson 35 Gold Belly ...
Bikes,Cars,Gunsmithing & Paintball...Oh yes, a 5Ha open air Workshop to play in!

glort

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Re: Induction Motor Generators
« Reply #8 on: August 15, 2018, 03:21:39 PM »

Hi Ed,

That was what I was back to doing.
Thought about running a genny with a rectifier  to make it DC then that through a solar inverter.  Bruce pointed out some problems with that which I later remembered I had before.  As such the best thing for boosting low solar output back through the mains meters is the IMAG directly connected.
I have done it before, have a vid somewhere of the meter at my old place running backwards doing it.

I know that used in C2C there is a lot of dropoff in output, like about half in practical output but do you know what the falloff directly connected is. I have it in mind it's pretty low like around 10-15%. Would that be right?

I'd probably be pushing the power down 2 Phases So I don't think the motor would start and certainly not the engine.  I have run 3 Phases motors before off single phase with no caps, you just need to give them a spin the way you want them to go before you add the power.  They run fine of course at reduced output.

An optical Tachometer would be helpful with this  so I could get the motor up to speed before I added in the power.  You are supposed to sync them from memory  if they are running before the connection is made but I find they give bit of a jerk as long as you aren't too far out and they then sync up.

I want to do a stand alone genny as well and I have got on to some of them finally thanks to Bob. The thought is to set them up either side of a motor and then have a change over switch if I want to run off the genny in standalone or just sync with the mains.

Really do need a bigger shed for these ambitions.