Dear All

Smart Line Modules can supply energy and return regenerative energy to supply system. Can somebody explain where this energy goes as "Returned to the System" means whether it is randomly distributed to other loads or some other theory works behind this. I could not get the correct idea from manual.

Regards

Huzaifa

In a common DC Link system, with several motor modules and one line module, it works as follows:

The Line module's job is to keep the DC link at a constant voltage.  It does this by taking energy from the incoming power line.  The motor modules provide power to the motor by taking energy from the DC link.

If one or several motor modules is braking, then they are taking energy from the motor and are charging the DC link.  If the energy provided by the braking is less than what is required by the other motors, then the other motors will continue to take the energy from the DC link.  The line module simply does not need to take as much energy from the power line to keep the DC link charged.  In this case, the braking energy from the one motor module is distributed to the other motor modules.

In the case where the braking energy from one motor module is greater than the energy required by the other motor modules, the DC link voltage will rise, since there is no other place fro the energy to go.  When that happens, the reverse bridge of the Smart Line Module will turn on and convert the excess DC link energy back to power to the incoming power line making the system into a generator.

A crane would be an example of a large braking load that returns power back to the line since, when lowering the load, the dominant energy is braking energy.  This energy would be returned back to the power line instead of being converted to heat through a dynamic braking resistor.

Hi,

We all know that when motor is braking or it runs due to high inertia load and we have removed line supply, the motor acts as a generator.

This causes regeneration. Regeneration mean, drive is giving reactive power back to the mains. It doesn't mean that it is providing power. But yes, we can say that it saves energy. As reactive power improves power factor.

Regards,

Krunal Shah

casajr

If it was purely reactive, then the DC link voltage would rise.

Do you mean that DC link voltage would NOT rise?

During braking, the DC link voltage would rise to whatever threshold level the reverse bridge is activated then remain constant until the braking energy is gone.  Then it would lower to whatever the unregulated rectified line voltage is as the motor modules are consuming the power.

Lets come to my original question, WHERE this energy goes as it says "Returned to the System". I got this that some energy if required by other motor modules is consumed, but what if they don't require this energy? whether this energy is distributed among other loads?

Regards

Huzaifa

casajr

Back to the power line.  The current reverses and you get paid for creating electricity back to the grid.    In reality, it gets absorbed locally by whatever else is connected to the same line, but I hope you get the idea.  You are a generator.

Hello everyone!

I find this discussion interseting , because I have always wondered HOW DOES THIS REGENERATIVE POWER ENTERS THE MAIN POWER LINE? IS IT SYNCRONIZED FIRST?

Yes of course.  Otherwise, explosions occur.

Think of it this way.  When a motor module is working, it takes DC voltage and chops it up into variable AC current and frequency.  When the regenerative bridge is working, it takes DC voltage and converts it to fixed frequency and fixed line voltage.

DC drives have been doing this for 50 years.  It is no different.  I have always wanted to take a cheap 4 quadrant DC drive and make it into an active AC drive front end.  Run it as a voltage regulator.  Sadly, I have never had the time or budget to do this.