AVR Testing

DIFINITIONS:1. Voltage regulation: In a power supply, the automatic holding of  of the output voltage to a constant value, despite variations in the input voltage or load resistance. resistance. 2.

Current regulation:

In a power supply, the automatic holding of  of the output current to a constant value, despite variations in the input voltage or load resistance. resistance. 3.

Automatic voltage regulator (AVR) :

An automatic feedback control system that is responsible for maintaining a scheduled voltage either at the terminals of  of a synchronous synchronous generator or at the high high--side bus of  of the generator stepup transformer. transformer. The control is brought about by changing the level of  of excitation excitation..

C.T. FEED BACK

V.T. FEED BACK

FIELD

INPUT (power supply)

C.T. FOR CURRENT FEED BACK SIGNAL TO AVR

GENERATOR V.T. FOR VOLTAGE FEED BACK SIGNAL TO AVR

EXCITER A.V.R.

A.V.R. DC O/P TO EXCITER

PERMANT MAGNET ( AVR POWER SUPPLY) PERMANT MAGNET THERMAL PROTECTION

PERMANT MAGN E T 

 AVR

FL ASHIN G

(I/ P  or P OW ER SU PP LY) is the method that enables the machine to build up its voltage.

To test  AVR we should provide the three indicated i/p elements : 1. Feed back signal from the generator o/p current.

2. Feed back signal from the generator o/p voltage. voltage. 3. A method to supply AVR AVR itself. The test we made ,was on the AVR of the emergency generator & its power supply is a permanent magnet type.

380/200v (voltage signal from Gen. o/p) M2 O.C. protection

M3 Trip/Reset

M5 M4 Main board Excitation o/p card

M1 Sensing & control

Filtering capacitor

Terminal strip

To supply AVR By 110v ac from Permanent magnet Rectification bridges

Variable resistor For tuning voltage

Variable resistor For tuning droop

Variable resistor For tuning gain

o/p dc voltage To Exciter

R

S

T

380v ac Gen. o/p voltage signal

Ac power supply I/P From permanent magnet

For simulation testing circuit ,we used: 1. 110v ac power supply that represents the permanent magnet supply.

2. 380v ac (R(R-S-T) that represents the voltage gen. o/p signal to test the main board. 3. Lamp at the o/p terminals.

The lamp position

Light  (The circuit is ok)

Dark  (There is a problem in the circuit) So check terminations ,transformers  , all cards ,capacitor   ,rectification circuit  & so on

We have a reference values which were taken from the actual operation from another tuned AVR works in the current time on the machine: 1. Be sure that the two V.T. s which feed by the Gen. o/p voltage to feed back the AVR By the voltage signal have the correct turns ratio ( 380/200v   for the new AVRs AVRs)) or (380/380v   for the old AVRs). AVRs). 2. If we applied the 73v ac on the AVR i /p terminals ((points points 11,12&13 in terminal strip) strip) We get 97v dc on the AVR o/p terminals (points ( points F1&F2 in terminal strip). strip). When making this test we cared about testing the all circuit of AVR so ,we only power Supplied the AVR by 73v ac on its i /p & noted the o/p (lamp position). If the lamp is dark We started to make our checks : signal )to )to test test the the the the V.T.s 1. At first we apply 380v ac (represents the voltage gen. o/p signal & the main board. If its ok ,we go to the second step 2. Check the filtering capacitor. If ok 3. Check the rectification bridges by checking its diodes individually (by measuring each diode between anode & cathode (0.7 v) between cathode & anode (open). Also by checking the bridges loop completely). If ok 4. By try & error check all cards M 1,M2,M3,M4 & M5. After finishing laboratory checks ,we must make an actual check on the machine to test If we get the wanted o/p voltage from the machine or not ,check the machine response & & also to check the machine stability at Running conditions under no load & load operation.