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When I search on web, I see three types of electrical braking exist for induction motors.

1-Regenerative

2-Dynamic

3-Plugging

Regenerative is said to be possible when rotor speed is higher than syncronous speed. What I want to ask in plugging braking (reversing supply flux direction) if it is possible to regeneration of energy. From my understanding, I can also regenerate kinetic energy to electrical one in plugging braking mode but I am not sure about it. I am waiting for your comments. Thanks in advance.

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The term regenerate is sometimes used rather loosely. All types of electrical braking convert kinetic energy to electrical energy. The differences are in the details of operation and the ultimate handling of the braking energy.

With the most strict definition of regeneration, the braking energy is returned to a source that can use the recovered energy rather than dissipated it as heat.

With plugging, the kinetic braking energy is converted to electrical energy in the motor rotor where is is dissipated as heat.

I believe that one form of dynamic braking involves shorting the motor leads of connecting a resistor across them. With those methods, the braking energy is dissipated in the rotor or in the rotor plus the external resistors.

DC braking involves connecting the motor to a DC power supply. I believe that is sometimes called DC dynamic braking and works similarly to other methods of dynamic braking.

When a motor is coasting at a speed higher than the synchronous speed for utility power operation, connecting the motor to the utility will result in the motor be braked to near utility synchronous speed with some of the braking energy being returned to the utility source and the remainder dissipated in the rotor.

Operating the motor using a variable frequency drive (VFD) provides similar braking methods with better performance and a higher rate a energy recovery in regeneration.

Re Comment:

In a VFD, the motor will regenrate braking energy to the VFD any time the output waveform frequency is below the frequency corresponding to the operating speed of the motor. A regenerative front end can return that energy to the connected utility source.

Conventional plug reversing is not an acceptable mode of operation for a VFD. However it is possible for a VFD to determine the speed and direction of a spinning motor and take control of it.

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  • \$\begingroup\$ Thanks for respond Charles, For example if I have an active front end module and vfd Can I just produce energy and feed back it to supply only in regenerative braking (rotor speed is higher than syncronous speed) or also in plugging braking (reversing supply flux and producing negative torque) I can feed back this energy to supply ? \$\endgroup\$ – d.alex May 3 '19 at 16:26
  • \$\begingroup\$ I added paragraphs to my answer. It is best not to expand questions. If you want to get further into VFDs it would be better to ask a new question with the VFD tag. You might also first look to see if you question has been answered already. \$\endgroup\$ – Charles Cowie May 3 '19 at 18:46
  • \$\begingroup\$ I don't think connecting a resistor to an induction motor will help to brake it. In any event, I tried using lightbulbs to slow down a larger (maybe 2hp?) radial arm saw. It didn't work.electronics.stackexchange.com/questions/156968/… \$\endgroup\$ – mkeith May 4 '19 at 4:34
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    \$\begingroup\$ @mkeith: My memory may have failed me. I thought I had read about braking by shorting or putting a low resistance across motor terminals. I know motors can contribute to short circuit current, but I found nothing in my file to describe shorting motor terminals as a braking technique. If it works, I assume it depends on residual flux in the motor and a quick transition from normal run to shorted. \$\endgroup\$ – Charles Cowie May 4 '19 at 13:55
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    \$\begingroup\$ @mkeith: I found resistive braking described by Raymond Horrell in Motor Application and Maintenance Handbook (R. W. Smeaton ed.) McGraw-Hill1969. Either power-factor correction capacitors or similar capacitance connected during braking is required. Some braking is apparently applied if a 3-ph motor with pf caps is disconnected without disconnecting the capacitors. \$\endgroup\$ – Charles Cowie May 4 '19 at 18:43

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