Using a VFD to load a genset. 3

[gruntguru]

I am looking for some advice on the above topic. We have an ABB regen drive (ACS800-11-0016-3) 15 kW and want to use it (in regen mode) to load a 3 phase diesel genset (18 kVA Cat/Olympian). We have had negative responses from ABB tech-help and a consultant. What issues can you see and what protection will be needed eg:
- preventing "islanding" in the case of power failure
- avoiding accidental "motoring" of the genset

Engineering is the art of creating things you need, from things you can get.

 

[Skogsgurra]

I do not have detailed knowledge of the specific drive. But if it is a true regen drive, which I have no reason to doubt, then islanding protection (usually high DC voltage protection) should be built-in.

Is motoring, aka 'dragging' the generator such a bad thing? If you need to avoid it, the torque limit can usually be set to allow only braking and no driving.

What are the specific reasons for not doing it that ABB and the consultant present?

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[waross]

Getting everything up and running may be a challenge. Does the VFD have the ability to connect to a motor "On the fly"?
A load bank will only consume about 5 liters an hour so there is not a lot of financial incentive to avoid a load bank for testing.
The VFD will be easy to control.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[gruntguru]

Thanks guys - very useful advice so far. The VFD would be operate on mains power so getting started should be as follows.
1. Start VFD
2. Set motor current to zero
3. Start genset
4. Select required (negative) torque or current setting on VFD to load genset.

Advantages of VFD over load bank
1. We already own this equipment. Load bank would need to be purchased
2. Stepless control
3. No heat to reject
4. Energy saving

ABB gave no reasons except "we don't have anyone using our drives for that". The consultant listed "motoring" and "islanding" as objections.

Engineering is the art of creating things you need, from things you can get.

 

[niallnz]

Hi Gruntguru
I think you will have problems as the VSD software is designed to control an induction motor, where as you have a synchronous generator attached your diesel engine. I am reasonably sure that you will damage the VSD if you connect it to the output of your alternator, whilst the VSD control software does do flying start that is on an induction motor that has virtually zero voltage on the terminals when it is rotating. IF you were to get this to work you would have to have the VSD running and synchronise the output of the VSD with the output of the alternator, then close a contactor between the two. ABB does make a synchronising kit for VSD's and you use the VSD's PID control to synchroise the output. BUT why use a VSD to load a generator?, just synchronise the generator with the network and adjust the fuel supply, there are a lot of controllers out there, that do the just that and provide the network protection.

Skogs, ACS800-11 is a true line regen VSD with active front end, in this instance gruntguru has a 16kVA 400V wall mount regen version of the ACS800.

 

[gruntguru]

Thanks niallnz. Neither ABB nor the consultant mentioned this as a problem.

Engineering is the art of creating things you need, from things you can get.

 

[Skogsgurra]

Good catch, niallnz!

I missed the synchronous generator part. All dynos I have seen have induction motors and connect to all regen drives with no problem.

But this is not a dyno. If there is no possibility to select synchronous machine operation, then it will not work.

Gunnar Englund

http://www.gke.org

--------------------------------------
100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...

 

[gruntguru]

From the ABB manual
Permanent magnet synchronous motor
Only one permanent magnet motor can be connected to the inverter output.
It is recommended to install a safety switch between the permanent magnet synchronous motor and the drive output. The switch is needed to isolate the motor during any maintenance work on the drive.

Engineering is the art of creating things you need, from things you can get.

 

[niallnz]

I'll assume that your VSD has the Permanent Magnet Synchronous Motor (PMSM) control software in it which is a special +code in the extended part number, but a PMSM motor is a very different beast to your synchronous generator. Not sure if the drive will like the low number of poles and high speed (in comparison to a PMSM, 180rpm vs 1500rpm). Your generator will have an AVR which will vary the field strength, where as a PMSM has a constant field strength. If this is ever going to work there are a lot of issues that have to be worked out. As I said earlier why use the VSD at all?

 

[gruntguru]

Thanks niallnz. What is your recommendation given that we would have to purchase the hardware required for the other options (genset controller or load bank)? Precise control is not crucial. We just need to be able to apply a range of steady state loads to allow us to perform tests on the diesel engine.

Engineering is the art of creating things you need, from things you can get.

 

[niallnz]

Why have you got the diesel engine? is it standby power, or is your line of business small diesel engine repairs and you need to do load testing but not the same degree as dyno tunning? In my opinion a 15kW (18kVA@0.8pf) load bank is going to be a lot less than synchronising and load controller. However, manual synch and load control could be done simply but as with all things in engineering there are risks and rules which you need to be aware of. A bit more information/back ground on your project and your location would be helpful.

 

[gruntguru]

I work at a University in Australia. We have a group researching early diesel fault detection by acoustic emission signature so their interest is the engine, the alternator is just a means of loading the engine.

Engineering is the art of creating things you need, from things you can get.

 

[niallnz]

I think that a load bank will be the cheapest and easiest way of loading the engine. But IF you do have the VSD AND it is a standard ACS800-11 AND you really want to, THEN replace the generator with a standard 15kW 4pole induction motor. This will let you operate the diesel at any speed you like AND load it at that speed which could be useful for you research. You will still be able to vary the speed with the load bank option but not over as wide a range as with the VSD as the voltage regulator will back off the excitation to maintain a constant V/Hz relationship, this will cause the load bank steps to be different to is marked.


I used to work for ABB (with drives) and now work for a consulting firm, can I get paid for this ;-) I'm just across the ditch from you.

 

[Skogsgurra]

Agree. An induction motor will turn that system into a dyno for diesel engines. That will be the best solution. By far. It will be green, too. And you can use an existing or second hand motor for lowest cost.

Gunnar Englund

http://www.gke.org

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100 % recycled posting: Electrons, ideas, finger-tips have been used over and over again...