Metering of Regenerated Energy From VFD

While regenerative braking is taking place, the meter runs sdrawkcab.

The quantity will be tiny in comparison with that drawn during running.

Here are three examples of significant energy recovery.

-An Unwind stand for a paper machine used to be a drag brake. We replaced it with a regenerative drive, 500 Hp. Average recouped energy is about 400Hp. That is significant.

-Dockside cranes (cranes in general) - The work used to lift a container is recouped in lowering the container back down. - motor size again about 400HP.

-Veneer lathe for plywood - peeling up to 10 blocks per minute - the inertia of the lathe is significant, and since you are accelerating and stopping the inertia 10 x per minute you see about a 20% energy recovery on a 300Hp machine - again significant energy recovery. ( This is even higher if you consider cooling requirements if braking grids are used.)

USA east coast commuter trains (and anywhere it is exported) use 4 quadrant controller in every car. The braking part dissipates the energy in large resistors running the whole length of every car.

Compared to the whole consumption, the braking part is miniscule. The savings on brake pads and less frequent replacement of the running wheel assembly is a main budget item.

So, mainly, it depends on the particulars of every proiect.

With a pump or other like driven apparatus you will not gain much if anything from a recuperative braking vfd, however if the pumps have a large heavy drive pulley that might take some time to spin down (ie flywheel effect) you might gain some, over a long time period, a fan or large centrifuge, cutter head, etc. will yield a good return.
Keep in mind that most of the energy will be lost in heat dissipated through the vfd's thyristors and heatsinks during spindown.
Diesel electric locomotives have the best recuperation because of the huge inertia they store, which is where recuperative energy originated.

The normal diesel locomotive does not store any power except in the form or inertia. The only one that will is the new GE hybrid units with a battery on board if and when they ever come out with it. Some Electric only units do have the capability of pumping power back into the grid, but these are only the AC units. The DC units use mostly resistors in the US.

Some applications of VFD's with applicable storage are Elevators. Ironically the energy recovered is mostly on the lift cycle when lightly loaded due to the counterweights. When heavily loaded it shifts the other direction, but not as much energy is recovered.

Dear Mr.AtulChahure,

What you have referred is correct.

But the regenerative energy is very tiny fraction and the Meter will show/record the differential consumption of power.

For example, if 10 Units is consumed, 0.45 Units is the re-generated power, the Meter will record/show only 10 - 0.45 = 9.55 Units only.

DHAYANANDHAN.S