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Take an electric motor connected to a big fly-wheel. When you are driving it, it has a lot of energy. The moment you stop the power, it still has that energy. The fly-wheel will start driving the motor, in exactly the same way as a crane load drives the motor.

I have seen this used in the past in back-up generators. e.g. Airport, hospitals. There is a big electric motor/generator which is driven by the power net and has a huge fly-wheel. The moment the power net stops, the motor becomes a generator using the fly-wheel energy. This lasts only a short time but just enough to start a diesel generator which then takes over: constant energy without the need to run the diesel generator all the time.

(p.s. The diesel generator was kept warm all the time by using pre-heated cooling oil. )


But how is electrical braking done and how does it cause declaration and regeneration? Does the input power to the motor have to be stopped for these to happen?

Regeneration means the motor starts generating energy instead of using. This by definition means the power to it is stopped.
Compare this to the standard 'generating' which means making energy with a generator by applying mechanical energy.

It also means the energy from the motor has to be used. If you just stop the power, leave the electric connections open there is no re-generation.

I have failed to find a you-tube demo but I have seen one myself. Take a DC motor with fly-wheel.

  • Spin it up, stop the power, leaving the motor wires open: the motor slows down in X seconds.
  • Spin it up, stop the power, short circuit the motor wires: the motor slows down in less then X seconds.

In the first case the energy is used by the friction of the system.

In the second case there is also friction but additionally it is generating electric energy which, through the short circuit, is converted into heat. Thus it slows down faster

Take an electric motor connected to a big fly-wheel. When you are driving it, it has a lot of energy. The moment you stop the power, it still has that energy. The fly-wheel will start driving the motor, in exactly the same way as a crane load drives the motor.

I have seen this used in the past in back-up generators. e.g. Airport, hospitals. There is a big electric motor/generator which is driven by the power net and has a huge fly-wheel. The moment the power net stops, the motor becomes a generator using the fly-wheel energy. This lasts only a short time but just enough to start a diesel generator which then takes over: constant energy without the need to run the diesel generator all the time.

(p.s. The diesel generator was kept warm all the time by using pre-heated cooling oil. )

Take an electric motor connected to a big fly-wheel. When you are driving it, it has a lot of energy. The moment you stop the power, it still has that energy. The fly-wheel will start driving the motor, in exactly the same way as a crane load drives the motor.

I have seen this used in the past in back-up generators. e.g. Airport, hospitals. There is a big electric motor/generator which is driven by the power net and has a huge fly-wheel. The moment the power net stops, the motor becomes a generator using the fly-wheel energy. This lasts only a short time but just enough to start a diesel generator which then takes over: constant energy without the need to run the diesel generator all the time.

(p.s. The diesel generator was kept warm all the time by using pre-heated cooling oil. )


But how is electrical braking done and how does it cause declaration and regeneration? Does the input power to the motor have to be stopped for these to happen?

Regeneration means the motor starts generating energy instead of using. This by definition means the power to it is stopped.
Compare this to the standard 'generating' which means making energy with a generator by applying mechanical energy.

It also means the energy from the motor has to be used. If you just stop the power, leave the electric connections open there is no re-generation.

I have failed to find a you-tube demo but I have seen one myself. Take a DC motor with fly-wheel.

  • Spin it up, stop the power, leaving the motor wires open: the motor slows down in X seconds.
  • Spin it up, stop the power, short circuit the motor wires: the motor slows down in less then X seconds.

In the first case the energy is used by the friction of the system.

In the second case there is also friction but additionally it is generating electric energy which, through the short circuit, is converted into heat. Thus it slows down faster

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Take an electric motor connected to a big fly-wheel. When you are driving it, it has a lot of energy. The moment you stop the power, it still has that energy. The fly-wheel will start driving the motor, in exactly the same way as a crane load drives the motor.

I have seen this used in the past in back-up generators. e.g. Airport, hospitals. There is a big electric motor/generator which is driven by the power net and has a huge fly-wheel. The moment the power net stops, the motor becomes a generator using the fly-wheel energy. This lasts only a short time but just enough to start a diesel generator which then takes over: constant energy without the need to run the diesel generator all the time.

(p.s. The diesel generator was kept warm all the time by using pre-heated cooling oil. )