Voltage Regulator: Replacement Question 1

[Viceng]

I am hoping to replace some old Basler voltage regulators (type SSR 63-12F) with some new DECS200 units. The DECS200 units have a start input unlike the previous SSR regulators. I was wondering if anyone had experience with such a replacement and if so if there is an issue with leaving the START contact asserted on the DECS continuously so as to mimic the older SSR? That is, rely on residual voltage.

Thanks for your help.

 

[catserveng]

Just finished a retrofit a few weeks ago replacing an analog Kato AVR with a DECS200 on a smaller steam turbine generator.

We setup the unit to normally operate in Start or Run all the time, we did install a Start/stop switch to allow operator to stop AVR for things like extended low speed operation times. Adjusting the volts/Hz slope and startup parameters can give you a very nice startup ramp with very little overshoot.

We did interface the Stop input with the generator protective relay to replace the original relay in the PM power supply to shut down excitation in certain fault conditions.

One word of caution, using Bestcoms for setup is great, but we have found it is picky about USB to serial convertors, I don't usually have an issue because I still have a real serial port, but I've gone thru a number of convertors to find the right combination for a given laptop.

Hope that helps.

 

[wbd]

We had the same problem with USB to serial converters on the DECS400 with the Bestcom software. Had to try serial. Also had a problem with the Fiberlink E360 program blocking the Bestcoms software.

 

[davidbeach]

I've had problems with USB to serial converters with many applications from many manufacturers. The problem there is much more likely in the converter than in the Bestcoms software.

 

[wbd]

sorry, should have typed, Had to try several brands of serial converters to find one that worked. Also check the pin configuration of your serial cable with the Bestcoms pin out.

 

[Viceng]

Thanks for the input catserveng,

Basic question: Why is it that the DECS doesn't treat a low voltage condition as a time when field forcing is required? Is it simply that it requires a certain p.u. current in addition to voltage to differentiate a start up condition from a fault?

Has anyone heard of placing a resistor in series with the field circuit to make up the required "minimum field resistance" of the DECS? If so, would there be any issues in placing the additional resistance there constantly, or should it be switched on when the DECS is running? If the field makes the "minimum field resistance" requirements would there ever be a requirement for such an additional resistance?

Much appreciated.

 

[Ceast]

The DECS 200 is a great product. Very flexible. Refer the the DECS 200 manual for excitor field resistance limits.

Not sure why you would want to leave the DECS output on continuously? Again refer to the manual for start/stop control and OEL & UEL limits.

 

[catserveng]

If your SSR's worked ok then the DECS should do fine, I've used DECS200 on CAT generators that by the book were outside of the field resistance limits, along with a few others.

Based on what I've seen the DECS sees the startup from a zero speed condition, while a transient is a deviation from normal operation with field output. I've found the Basler folks to be very helpful in explaining how their DECS and other products work.

I think it can be a bit challenging for the first few times, but it is very capable, and just make sure you give yourself enough time and resources to get it adjusted and tuned for your application. There are some very good tools in the Bestcomms, I also find a chart recorder or some other way to visualize the response helpful in tuning dynamics.

Hope tha helps.