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VSD Regenerative Discharge


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Hi Everyone,


Is there anyone of you familiar with technology of saving energy normally discharged to braking resistors of variable speed drives?


I'm from an industrial automation systems integration company. I have a client with a galvanizing line for continuous steel sheet which are normally cut and corrugated into GI sheets for roofing. In the said line they have 33 motors from 40 kw to 150 kw, each driven individually by vector drives (Eurotherm/SSD 690+). The line has synchronized speed from the unwinder to the rewinder, with a plc providing the line speed setpoint and the drives interlocked to one another for their actual speed.


My client told me that a supplier informed him before that the energy usually discharged to braking resistors of VSDs can be collected back from the DC bus terminals, be converted to AC and fed back to the power system. In this way energy that would have been dissipated to heat is converted back to useful electrical energy which could probably save money, depending on how much is really recovered.


Can anyone point me to any reference, white paper and the like, on how to go about in actually installing this kind of energy saving system?





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Hello Gerry


Welcome to the forum.


This is definitely possible and is often referred to as "active front end drives".

You can use a drive such as the Control Techniques SP drives in a regenerative mode to return power back to the AC supply.


You need to connect the DC bus to the DC Bus of the SP drive with the output of the drive connected via reactors to the supply. The SP must be configured for regeneration and it will work well.


One of the first steps to take, is to parallel connect all the DC buses of the drives. That way, if one drive is motoring and another is braking, the motoring drive can use energy from the motoring drive rather than from the main supply. This will reduce the power draw. If there is still a regeneration problem, then add an SP or two in regeneration mode to return excess energy to the supply.


U2U me with your email address and I will send you the regen manual for the SP.


Best regards,

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Hi Gerry,

U2u did not get to me.

My email address is empson [at] LMPhotonics [dot] com


replace the [at] and [dot] with @ and .


Best regards,

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