AC Gen

Question 1

Require of V?

Answer 1

• 450V
• Line vari less than 1%
• SS V between 57-63hz
• Transient V vari max of 7.5% for 25% load go off & 15% for go on load
• Time of recovery to 1% of final V ,less than 1 sec

Question 2

Req of Hz?

Answer 2

• 60hz
• ss Hz vari 3.5-4%
• TRansient hz vari for 25% load changes +- 2.5%
• Time of recovery for transients to within 1%

Question 3

Operation of brushless gen

Answer 3

• PM rotates shaft 1200
• PMG supplies exciter by the AVR
• AVR supplies DC V to exciter stator
• Exciter rotor produces AC V
• Goes into rectifier AC-DC
• DC onto gen rotor inducing mag field
• Inducing EMF In stator
• 450v,3ph,60hz to swbd
• AVR monitors v output by sample line from gen stator

Question 4

Fault cond on rectifier

Answer 4

• Open-V fall,Excit overld,damg diodes,sup brkr open
• Short-V fall,AVR comp,diode strain,gen off within 30 mins

Question 5

Gen rounds

Answer 5

• Monthly-VA records,Bearings,water,vent grills
• Dailies-Bearings,air temp,oil temp,leaks,diode fail,heaters not on.

Question 6

AVR Modules & what do?

Answer 6

• 17 FU=improve HF 160hz sup
• 1 EC=connects 160hz to mosfets
• 28 CU output con=provides firing pulses to mosfets
• 169p output power amp=4 mosfets
• 41 mu=ensure param
• 1PN=shut dn
• 1 UF interfce=provides V + hz to avr modules
• 168p Low v pwr supp=24VDc to modules
• 1CU comp unit=compares actual v to des