Pleading ignorance. Difference in induction motor vs generator?
Pleading ignorance. Difference in induction motor vs generator?
(OP)
I am sure there might be some basic adjustments to optimize one or the other like bearings and such, but I was sort of lead to believe there are quite a few differences here? It was my understanding that these are effectively the same thing, just depending on which side of synchronous rotation the rotor is on? Leading or lagging? If I have brought an elementary question, please forgive me!





RE: Pleading ignorance. Difference in induction motor vs generator?
RE: Pleading ignorance. Difference in induction motor vs generator?
Given that, many forms of small (single phase mostly) electrical machines do not meaningfully convert mechanical energy to electrical energy. Generally most 3-phase machines can be either motors or generators, some performing both roles multiple times per day. The standard 3-phase induction motor can function as a generator if driven above synchronous speed and supplied with an external source of excitation (vars). A synchronous machine has a rotor with a field and does not require the line to supply excitation.
A synchronous generator can generate both Volts and Watts while an induction generator can only generate Watts, the Volts have to be supplied by an external system.
DC machines are a different animal, but follow that basic definition.
RE: Pleading ignorance. Difference in induction motor vs generator?
CR
"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]
RE: Pleading ignorance. Difference in induction motor vs generator?
I did look up the rotor wound or dual wound motor and seems to be most common with variable rpm situations as it can generate power in a much wider range than a wireless rotor.
Just for consideration (no, I don't have a specific application), if an induction 'motor' is driven at near continuous synchronous speed, would there really be any practical difference to a generator? Wave form, efficiency, generated available power, etc?
RE: Pleading ignorance. Difference in induction motor vs generator?
RE: Pleading ignorance. Difference in induction motor vs generator?
Sorry tug but an induction generator does not need a wound rotor.
There may be designs that optimize induction generation, particularly some wind turbine induction generators.
I have set up induction generation demonstrations for students.
In one school lab, I was able to demonstrate induction generation and with a resistor bank in parallel with the motor, the motor, acting as an induction generator continued to power the resistor bank when disconnected from the line.
(The motor was being driven over speed by a DC motor.)
In both cases I used available induction motors over driven by DC motors.
In different school lab, I was able to demonstrate induction generation. With the equipment available I was not able to continue to power the resistor bank when the induction generator was disconnected from the line.
Given the wide range of standard and special designs of rotor squirrel cage windings, I would expect some designs may be more efficient than others for regeneration.
Hopefully one or more of our motor design Gurus will have some information as to optimizing motor design for use as induction generators.
Bill
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"Why not the best?"
Jimmy Carter
RE: Pleading ignorance. Difference in induction motor vs generator?
Traction elevators may be the most familiar example of a squirrel cage induction generator/motor. Consider an empty, or lightly loaded, elevator. Every time it goes up the "motor" is a generator and power is returned to the supply system or burnt off as heat and every time it goes down the motor has to function as a motor. Heavily loaded it's the opposite.
RE: Pleading ignorance. Difference in induction motor vs generator?
RE: Pleading ignorance. Difference in induction motor vs generator?
RE: Pleading ignorance. Difference in induction motor vs generator?
I energized the motor and the resistor bank. Then I powered the DC motor and increased the speed until the induction motor was acting as an induction generator and exporting power to the grid. I forget the details but I had a lot of instrumentation connected including a Wattmeter.
We saw power being returned to the grid. Then we opened the connection to the grid. The load current provided the excitation and the induction generator continued to power the resistor bank.
Note that the purpose of the demonstration at that time was not to demonstrate induction generation but to impress upon the students the fact that induction motors can and will back feed into a short circuit.
I understand that with some induction generators the residual voltage in conjunction with suitable capacitors will boot-strap and build up voltage without outside excitation. This is something for us both to watch for credible supporting information.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Pleading ignorance. Difference in induction motor vs generator?
" We are all here on earth to help others; what on earth the others are here for I don't know.
" -- W. H. Auden
RE: Pleading ignorance. Difference in induction motor vs generator?
It was plain 'off-the-shelf' induction motor.
We added metering to measure power in or out. Overload protection was a standard thermal overload block a magnetic-only motor circuit protector.
old field guy
RE: Pleading ignorance. Difference in induction motor vs generator?