Dynamic braking on AC line

[LMAO]

Does anyone know if there is an off-the-shelf chopper (braking module) that would connect to AC line? There is an application where large DC drives running DC motors are connected to 600V generators. These motors can have significant reverse power at times and manufacturer of DC drives has confirmed the drive can regen the power back to line but the problem is this obviously can damage the generators. DC drive manufacturer does not have any solution because they say their drives are usually used on utility where reverse power is not a problem.
Does anyone know of an off-the-shelf "AC" chopper with built-in power transducer that can sense the reverse power and turn on braking resistors? Or, maybe a stupid question, is it possible to connect regular choppers (with DC input) to the motor leads (aka, in parallel with DC drives)?
We already have a solution which is a combination of a rectifier, PLC, power transducer and resistor bank along with some current transformers. PLC monitors the power flow and turns on the rectifier on resistors to dissipate the power but this requires engineering and product support.

 

[petersonra]

why did you buy 4 quadrant drives if you didn't want them to regen back to the line?

you might be able to disable the rectifiers that are only used to regen back to the line.

bonitron makes all kinds of braking modules that might be used to get rid of the excess energy once you disable the regen rectifiers.

 

[Jraef]

I think you need to look at a "load bank" for that. It's the same sort of thing you would use to exercise or test the generator.

 

[jimo144]

Dynamic braking on AC line

With 600 VDC you are positioned right in the normal operating range of Diesel Locomotives. The reverse feed or Counter EMF typically takes place when the DC Motor has it's power feed interrupted and the Iron of the Motor still has Magnetism and / or the motor is being turned by the movement of the Locomotive. The Magnatism turns the DC Motor into a Generator. The Counter EMF will continue, gradually powering down until the Magnetic Flux Decays.

I would look into a simple Load Bank Resistor and DC Dynamic Brake (DB) Power Contactor as used on Locomotives. They have Magnetic Arc Chutes to control the Counter EMF without damage and expected Life Cycle for these Contactors is Decades. You could create a control Circuit to Drop out the AC Powered Circuit and Bring in the Resistor Grids VIA the DB Power Contactor.

Locomotives typically have a 74 VDC Control Voltage. You can create a DC Power Supply by using a Half Wave Diode / Rectifier Circuit on a 120 VAC power Source. The 74 VDC Coils typically have a Pick Up Voltage around 48 to 50 VDC so the approximate 60 VDC from the Half Wave Power Supply will work very well even without Filter Capacitors.

The DB Power Contactors are plentiful in the Rebuilt Locomotive Component Market. I use K&L Electronics (501) 368-8262. The DC DB Grids are relatively inexpensive for the application. I use Moseback Manufacturing at (412) 220-0200.

If you decide to go this route, I could give you Locomotive Part numbers.

JimO

 

[Sahib]

There is an application where large DC drives running DC motors are connected to 600V generators. These motors can have significant reverse power at times and manufacturer of DC drives has confirmed the drive can regen the power back to line but the problem is this obviously can damage the generators.

Other loads, if any, connected to 600v generator can absorb excess power, thereby preventing any damage to generator and thus could solve your problem.

 

[petersonra]

I wish posters would come back and tell us how they solved their issues.

 

[ggunn]

There is a new library nearing completion here in Austin which is very "green", with lots of natural lighting, a PV system, and regen braking on its elevators. It's also on the Downtown Network, which means it can never export power to the grid, even for short periods of time. Coordinating the PV system and elevator braking with the power usage of the building is a nontrivial task.