Hi All,

I am setting up a Drive test bench in my factory and I am planning for regenerative drive sytem.
Basically my idea is to couple shafts of 2 motors (test motor and load motors). For a test motor I will use AB Power Flex drive and the load motor which generates power back to bus will be ABB ACS 800-11 drive. This drive has active filters which feeds the power back to bus.

I am not sure of my setup as I have not worked much with drives. Here is my setup idea:

Motor shafts will be connected directly with shaft coupler.

To load the test motor first I will start test motor drive (running in forward direction).
Load motor drive will remain stopped.
Once the test motor is at full speed at full load (i.e load motor is not running) then a start command and speed reference (reverse direction direction) is given to load motor, which will assist the test motor.
By giving different speed references to load motor drive I can load the test motor.

Please give me your feedback for this setup.
With zero speed reference of load motor drive I should be able to get power back from ACS800-11 DRIVE to BUS. Am I right here? Or do I need any extra setup?

SCAN_PLC

 

I think that you really want to control torque using the ABB drive instead of speed. That is the best way to apply a load.

 

Depending on the size of motors in the application you should use the Unidrive SP from Emerson/CT... if this doesn't fit the bill then let me know and I'll look for something else. Emerson specializes in regenerative/common bus systems, and with the Unidrive SP you can have one type drive do everything... your system will be common vs. using one AB drive and one ABB drive. You will want to use vector motors if possible (encoder feedback) for good control.

Technially, you probably don't need a true regenerative drive... what you need to do is a "common DC bus" system with Unidrive SP (or with two AB or two ABB drives since you don't need a true regenerative system). Because your test stand can not create power... over simplified its like this: The power from the load motor drive is regenerated (common DC bus shared) to the test motor drive... due to heat losses you will use minimum power but not generate... if you can generate it let me know... and we'll work together on making a mint.

Based on applications that I have done that are similar to the one you describe, you are pretty close. But the key to remember is that Load is Torque. If you command a "load" motor speed lower than the "test" motor (whether it be zero speed or slightly less than the test motor, i.e. 5%)... then the load motor will continue to try to drive to that speed... eventually going into a current limit of a default parameter of 115%-800% (depending on the drive you use)... and that will eventually fault out the load drive. So to properly load the test motor you will need to do some mechanical calculations to see where you need to change the default torque/current limit on the load drive to!

B

 

Hi B,
The reason for using two different (ABB and AB)dirves is the distribution rights that my company has with these drives comp.

Now coming back to connecting the DC bus together of 2 ABB drives seems to be staright forward and simple. But what I read from the Manual of ACS 800 -11 is some thing like this.

The IGBT supply module is a four-quadrant switching-mode converter, i.e. the power
flow through the converter is reversible

and this as well

The regenerative drive offers significant energy savings compared with other braking methods such as mechanical and resistor braking, as energy is fed back to the AC line network.

From this test bench in which both AC drives are connected to AC Bus (DC bus not connected ) is to demonstrate

1. Tourque control of drives by varying the load on test motor with load motor (Drive in Touque control mode ). Should i couple shafts directly (mechnical cuoupling of shafts and motors roating in opposite direction for load testing )or should i couple the shafts with belt with both motors rotating in same direction.I could not understand here what difference in these two setups -I hope some one can give me more info.


2. To demonstrate drive power regeration back to AC bus. (ABB drive in regenration mode )
Will I be able to feed power back to AC bus from ABB drive and how i can read this power back on AC bus.

thanks in advance
scan_plc

 

In most cases the tiny amount of energy recovered is never worth the captial cost. However, sometimes you can avoid an expensive brake resistor, which might make it worthwhile.

Often, as the other poster sugegsted, a common bus system makes more sense.

 

scan_plc

So are you using two ABB drives now? Yes from what I understand ABB makes a 4 quadrant drive.

So the Load drive will be in regeneration mode most if not all of the time...so this drive will need to be a 1) a regenerative drive as you state or 2) common DC bused to the Test drive...either will work, you just need to dissipate the regenerative energy somehow...and you are correct a regenerative or 4 quadratant drive that is regening all the time as a Load drive is more energy efficient (than a resistor or mechanical brake/clutch etc.) because that power is being reused....the same goes for a common DC bus system...

The reason I recommended a DC bus system is due to the $$$ and the application....if you common DC bus you DO NOT need a fully regenerative or 4 quadrant drive (for the load or test) which leads to a lower cost system....hopefully that makes sense.

If not maybe you should contract me to do the design for you....hah gotta love it.

You can directly couple them end to end or side by side with a belt either way...it simply changes the sign of your speed and torque limits and/or commands...I've personally tested in a shop side by side, then went to the customer and ran it direct coupled by swithing the signs on a few parameters....however you may consider the mechanics of the two depending the applications...which I can't answer for you.

So onto control mode....
1) Again, I would do straight torque control...I assume you want to test the motor at X speed with a load of Y etc... so you will want to command the test motor to go to X speed...then the load motor to go to X - 5% (X minus a percent or plus a percent)...so it will try to drive the test faster, and test will try to drive the load slower or vice versa etc. Where the loading part comes in at is you will need to limit the torque of the load drive/motor to Z% (Z percent) so will actually be testing it....this maynot be exact but it is pretty close to what you will want to do.

The reason I prefer this way is it gives you a speed limitation vs. pure torque control will allow the motor to run away very quickly if the load is lost somehow etc...

2) The ABB drive should (If it is like others) have a parameter that directly shows the power going back to the line...don't know why you would want to look at that for the application though....you will probably look at the torque that the load and or test drives are pulling/regenerating....if you look at the AC regen side there are probably small loses in the drive...so not sure what you're trying to do here?

 

scan_plc,
I would like to know about your experiment more, I have the conceptually similar requirement for testing induction motor.

Regards,
shashank

 

dear friends

1) drive motor should be a constant speed. and the drien (load motor) based on torque mode. by follow this steps we can get a loop operation like hand shaking between two drives.

2) ATV71. ACSM1. recently Delta having the DC bus sharing facility. but use the same model drives for easy operation.

3) regeneration take place only above the syn. speed. if you run the motor not the multiple of drive motor frequency (drive is 30HZ, then driven not more than 30. but both motor should same pole).

4) i seen a same application done by using ACS 550 ABB drive (45KW).