Static Thyristor AVR

[burntcoil]

Greetings,

We are working on a Diesel Engine Generator rated 13.8kV, 4785kVA. The unit was installed in 1980s. The generator have a static thyristor automatic voltage regulator from Brush Model#9603638. Please provide me with the Manual/Brochure for this AVR if anyone if you have.
Also I need Engine Supervision Unit Manual/Datasheet. Manufacturer: KUHSE, Model: KEU 341 FE24

Thanks

 

[ScottyUK]

That's probably a contract number or a drawing number, not the AVR type. At a guess it will either be a MAVR or PRISMIC model. Can you post a photo - I'll probably recognise it.

I have a MAVR manual somewhere, although for a much bigger machine. Brush at Loughborough should have these manuals readily available - their archives are pretty good, certainly for a fairly recent set.

 

[burntcoil]

STAVR Pic attached.

 

[burntcoil]

Attached is the drawing showing the wiring for AVR. The AVR have an input from CT and VT. I have the following questions.

1. What is the difference between Voltage Setting Potentiometer and Hand Control Regulator. The Hand Control Regulator is installed on the panel door (Make: Regavolt Transformer)and it have a scale of 0 to 115V.

2. "Diode Failure Indicator is for monitoring which diode? Can I take it out in the new design where we will use a Genset Controller to upgrade the generator control.

3. How the AVR output is varying based on CT/VT input?

Thanks

 

[burntcoil]

Hand Control Regulator

 

[ScottyUK]

Hmm, that's not quite what I expected. Definitely not a PRISMIC, and doesn't look like a MAVR from the photos although there are constructional similarities. I didn't realise they had a smaller AVR although it makes sense because they absorbed Electric Contruction Company in the late 70's / early 80's.

The failed diode indicator measures ripple in the field circuit, so it will be monitoring the half-controlled rectifier powering the field. You can remove it, or find an AVR with the feature built in. Even on their larger AVRs the diode monitoring wasn't flawless and I've seen false alarms and also a few occasions where it didn't see the fault. I didn't trust it. If you want to know what is going on in the field with more certainty use an isolated scope for voltage measurement and a current probe.

The voltage setting pot. sets the reference for the automatic regulator which operates in closed loop to maintain that setpoint. The hand control regulator is exactly that - you control the field directly, and you provide the feedback loop via your eyes and your arm.

The VTs close the feedback loop for automatic control. The CT is probably to aid sharing of reactive load when machines are operated in parallel - look up 'quadrature current compensation'. There is a trimmer marked QCC on the circuit board which is associated with this control.

 

[glendale]

The AVR is a BRUSH Static Thyristor Automatic Voltage Regulator (STAVR) and was manufactured by them to provide excitation generally to salient pole generators fitted with a permanent magnet generator.

1. The Voltage Setting Potentiomeeter is the +/- 10% voltage adjustment of the AVR, the hand control regulator is a standard auto transformer (variac) that is only used when the excitation system is switched to manual.

2. The diode failure indicator was as Scottyuk said was a simple method of detecting a failed (open circuit) rotating diode (or fuse) by detecting AC ripple induced back onto the exciter field supply from the AVR, an alarm was considered to be sufficient as the excitation is virtually unaffected by the loss of one diode or fuse.

3. Exactly as per Scottyuk comments.

The AVR has since been replaced with the BRUSH PRISMIC range of excitation systems. Contact Chris Lewis at BRUSH Electrical Machines for further support.