TD-2 MICROWAVE RADIO RELAY SYSTEM 



1073 



engine alternator or diesel alternator is warmed up and assumes the load, 

 at which time floated operation is resumed. An important characteristic is 

 the absence of any direct switching in the load leads during power failures. 

 The control equipment in all three battery plants is arranged for full auto- 

 matic operation and additional charging rectifiers are switched in and out as 

 required. After a power failure the rectifiers operate at full capacity until 

 the battery is recharged, after which normal floating operation is resumed. 

 Sufficient capacity is normally installed to give at least an eight-hour reserve 



RECTIFIERS 



COMMERCIAL 

 POWER 



H 



TRANSFER 

 CONTROL 



ENGINE 



ALTERNATOR 



EMERGENCY 



POWER PLANT 



120 

 VOLTS 



+250 VOLT 

 PLATE SUPPLY 



56 CELLS. 



KEY 



INTERLOCKED 



SWITCHES 



130 

 VOLTS 



.56 CELLS 



+ 130 VOLT 

 PLATE SUPPLY 



63 CELLS 



24 



VOLTS 



-24 VOLT 

 MISCELLANEOUS SUPPLY 



11 CELLS- 



12 

 VOLTS 



6 CELLS- 



J 



T 



-12 VOLT 

 HEATER SUPPLY 



Fig. 22 — Power plant block diagram. 



to allow an attendant to get to the station in the event that the engine 

 alternator fails to start. 



A. -12 Volt Supply 



The — 12 volt heater supply consists of six battery cells floated by two or 

 more parallel-connected 200-ampere full wave selenium rectifiers. The out- 

 put voltage of the rectifier is controlled by a saturable reactor and regulating 

 autotransformer in series with the primary of the stepdown power trans- 

 former which supplies the selenium bridge rectifier. The output voltage is 

 automatically adjusted by the amount of d-c. current supplied to the satu- 

 rable reactor by the electronic feedback control circuit in the rectifier. The 



