Why can't a 2 pole ac induction motor run a 6 pole induction generator

  • #1
TL;DR Summary
The argument is, if I have a 2 pole, 2kw motor, shaft connected to a 6 pole, 4kw generator, why will this not run?
I will use examples of actual products:

1) 3 hp (2.2kW) 3 phase 2 pole AC Induction Motor
3 hp/2.2kW three-phase induction motor features 2 poles, 2840rpm rated speed, and 7.4Nm nominal torque, with a working voltage of 380V 50Hz. Cheap 3-phase asynchronous motor has outstanding performance in the price, maintenance, reliability, durability, and operation.

2) 5 hp (5.5kW) 3 phase 4 pole AC Induction Motor
Cheap 3 phase AC induction motor or asynchronous motor, 4 pole 1440rpm, squirrel-cage type, 7.5 hp (5.5kW) nominal power with 380 Volts @ 50Hz voltage, Totally Enclosed Fan Cooled Enclosure, foot mounting, high-efficiency performance, high starting torque, little vibration, and reliable operation.

What I will then do is, turn 2) into a generator that is self-excited and use 1) to operate it.

With the idea that I only need the torque from 1) to get 2) to 103% of 1440 rpm.

Is this possible?

if not, why?

If so, why?

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  • #2
I'm not sure about your details. But you can't violate conservation of energy ever. Meaning, you can never get 4kW from 2kW, no matter what kinds of devices you use.

Also be reminded that free-energy, perpetual motion, and over-unity power gain are all forbidden topics here on PF.

So, is your meaning to get more power out than power in?
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  • #3
To generate 5.5 kW from 1440 rpm you need a minimum torque of 5.5kW/(1440*2pi/minute) = 36.5 Nm. More if you take into account that the generator is not 100% efficient. Not surprisingly, you can't get this with half the input power.
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  • #4
Elijah Castiel said:
if I have a 2 pole, 2kw motor, shaft connected to a 6 pole, 4kw generator
If you put 2kW into the input motor, at most you can get 2kW out of the generator that you drive with that motor's output shaft.
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  • #5
Thread closed because it violates PF guidelines.

1. Why do 2 pole AC induction motors and 6 pole induction generators not work together?

The main reason is due to the difference in their design and function. A 2 pole AC induction motor is designed to convert electrical energy into mechanical energy, while a 6 pole induction generator is designed to convert mechanical energy into electrical energy. This fundamental difference in their purpose and design makes them incompatible with each other.

2. Can a 2 pole AC induction motor be modified to run a 6 pole induction generator?

No, it is not possible to modify a 2 pole AC induction motor to run a 6 pole induction generator. The number of poles in a motor or generator is determined by the number of stator windings and the arrangement of the poles. Modifying the motor would require changing its fundamental design, which is not feasible.

3. Are there any other factors that prevent a 2 pole AC induction motor from running a 6 pole induction generator?

Yes, apart from the difference in their design, there are other factors that make it impossible for a 2 pole motor to run a 6 pole generator. These include the speed of rotation, the frequency of the electric supply, and the number of magnetic poles in the rotor. All of these factors need to be in sync for a motor and generator to work together.

4. Can a 2 pole AC induction motor and a 6 pole induction generator be connected in any way?

No, these two devices cannot be connected in any way as they have different electrical requirements. The motor needs a constant supply of electricity to rotate at a high speed, while the generator needs a mechanical input to produce electricity at a specific frequency. Connecting them would lead to damage to one or both of the devices.

5. Are there any alternatives to using a 2 pole motor and a 6 pole generator together?

Yes, there are alternative solutions that can be used to achieve the desired outcome. One option is to use a variable frequency drive (VFD) to control the speed of the motor and match it with the frequency of the generator. Another option is to use a gearbox to increase or decrease the speed of the motor to match the requirements of the generator. Both of these solutions allow for the use of different types of motors and generators together.

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