Suitable replacement for a Caterpillar DVR 2

[gentech]

I am looking for a less complex analog replacement for a Cat DVR which drives a 450 kW SR4B alternator. I will be using a Woodward Easygen control and don't want/need the added complexity of the DVR. Does anyone have any recommendations? Thanks.

 

[catserveng]

A CAT VR6 will work well in conjunction with an EasyGen, Basler sells a commerical version of the VR6, the AVC63-12.

I've replaced a large number of the older DVR's with VR6 regulators with little or no problems.

One recommendation I would make is to get rid of the CAT droop CT and install a properly sized 5 amp secondary CT, probably a 600:5 for you size unit. You'll find the droop function works better and if you're using the Easygen to control VAR's or PF if paralleled to grid or another unit you'll have better control.

Here's a link to the Basler manual,

http://www.basler.com/downloads/9337200991E.pdf

You'll have to register with Basler to download it, but I think it's a better manual than the one CAT supplies for the VR6.

Hope that helps, Mike L

 

[gentech]

Thanks catserveng! I was hoping to get by with 0 droop when in single unit isolated too. My thought being that the easygen will control the voltage according to set point, PF will be what ever the bus dictates. Have you seen stability problems with something like this?

 

[Ceast]

Yep VR6 is the bomb and inexpensive. A little droop is a good thing.

 

[catserveng]

I agree with Ceast, "a little droop is a good thing".

In my experience not having a small amount of voltage droop when using an external control tends to cause stability issues. Because so many things influence dynamic response it's hard for me to give you a rule of thumb that will work all the time, but I usually start with about 3% voltage droop (roughly a third turn of the droop pot on a VR6), and adjust based on how the system responds. If you want zero droop when the generator is the only source, just put a relay in the droop CT lines to the AVR that shorts them when you don't want the droop feature active.

My only grief with the EasyGen is that when you use the analog voltage bias it sometimes wants to drive the voltage, so you'll need to look at the EasyGen settings and may have to detune them a bit. Otherwise you can end up with a voltage oscillation as the EasyGen and the AVR work against each other. Doesn't happen all the time, but be aware of it.

If you go with the VR6, set the stability pot to mid-scale to start, don't connect anything to the voltage adjust pot input (leave the jumper on) and use the aux input on the VR6 for to signal from the EasyGen.

If you contact Woodward for interface info, you'll likely get a diagram showing an interconnect between a CAT VR6 and a EGCP 2 controller, unless they finally updated it. The easyGen documentation is pretty generic, but I know Woodward is trying to get it better.

Mike L.

 

[gentech]

Thanks again. The PWM signal for the ADEM is in the easygen documentation, I appreciate the info on the interface with the VR6/AV63, and the feedback on the droop.

Don't know if you can speak to this or not but I've noticed remarkable similarities between the subpan mounted easygen and the control in the ISOlynx Cat/Cutler Hammer gear, both physically and functionally. Any idea if the easygen will communicate with the ISO gear?

 

[catserveng]

OK, I'll start this by saying I am not a fan of CAT/ISO switchgear, cost me a lot of greif over the years, so my opinion my come of a bit negative.

ISO used a custom version of the EasyGen for a number of years, a lot of problems, mostly in trying to make a realitively small control do way too many things in my opinion, caused a lot of end user issues.

Woodward released the commercial version of the EasyGen and so far, other than a few glitches, it has done pretty well I think.

CAT/ISO has, from what I've heard, backed away from the 3.S control based switchgear and are going back to more traditional designs. Don't know the full story there, but what you're looking at in your gear is a custom programmed backplane mounted EasyGen done exclusively for CAT/ISO, called the 3.S control, or EMCP 3.S.

Hopefully your gear is meeting your current needs, my experience with that type switchgear overall has been very poor, and have done a few major rip and tears for customer fed up with it. If you're still active military you probably ended up with one of the Defense and Federal Products package systems, so many versions went out hard to keep up with them all but some worked great others were real POS.

I assume you are likely in the Army or Air Force portable power group? Good luck with your project.

Mike L.

 

[gentech]

Catserveng,

I am still active, a Navy Seabee. Shore based prime power production. 2 and 4 stroke diesels, 2500 kw, low and medium voltage.

We train with the Army for prime power production and then go more in depth into medium voltage substations and isolated and grid tied multiple unit plants.

The ISO gear I'm dealing with, from the drawings I've seen, seems fairly straight forward. Power modules with ISO switchgear to tie to the load. ISO gear has one current/voltage analogue to digital converter (ISOlynx box)per power module with a PLC. What I haven't seen yet is are drawings of the module. My guess from the drawings is that there is also a digital box in the module to communicate with the ISO switchgear so that the gear works as a plant.

My root issue is if I present standard CAN or modbus registers to the ISO gear will they play nice with a woodward control?

For business reasons I can certainly appreciate I have yet to have been able to get an answer I can build a technical plan to build on regarding communication with the ISO gear.

I could always use a droop governor and droop ct with an operator against the grid, or an isoch unit with some droop units against an isolated load, but where is the fun in that? I was taught on Woodward UG8 governors and droop regulators. I find today that even the most highly priced service techs, and even some engineers, sometimes don't understand analog paralleling.

Thanks again!

 

[catserveng]

Not sure what vintage of the Power Modules you're dealing with with ISO switchgear. My experience with the early ones was very poor, had two units in parallel during a utility outage at a hospital and they decided to go out of parallel mode and into island. Was a tough night but we got thru it. Overall the hardware is ok, some of the programming really sucked. I converted four of the units to Woodward controls with Allen Bradley MicroLogix PLC's, never had anymore trouble with those. I left the dealer shortly afterwards and I haven't done much with newer power modules since. I still help a number of dealers and end users with older utility grade modules, mostly conversions to replace the older Siemens PLC.

If you continue running into issues with the ISO gear, there is a guy at ISO named Dale Hrachovek, give them a call and ask for him, he'll be able to get you some help if needed.

I've done a huge number of paralleled power modules, in groups islanded and tied to differing grids, from utility substations on very good networks to Pacific Island grids after bad storms, I think someone at CAT tried to make the power in a box do a few too many things. My two cents worth.

I did some training on a new style CAT powered MUSE unit at Port Hueneme a few years ago, you weren't by chance involved with those were you?

Good luck in you efforts, Mike L.