3. Battery Charging Unit
A. The battery charger is a regulated system designed to charge nickel-cadmium batteries. The charger operates from a power source of 200 volts, 400 Hz, 3-phase, Y-system, 115-volt phase to neutral. The charger has two operating modes, which are externally controlled. Two types of chargers are available for use. One type is designed to charge a nickel-cadmium battery and maintain the charge by means of externally controlled pulses. The other type is a limited pulse type charger designed to operate with a nickel-cadmium battery and is optional to and interchangeable with the first type. In addition to the external mode control, the limited pulse type charger has an internal mode control, which causes the charger to operate in the normal mode for only a limited time after pulsing has begun. After this limited time, pulsing ceases and the charger operates in the high temperature mode. Pulsing begins when the battery approaches the fully charged condition and the charger output current is approximately 16 amperes. The output voltage regulation curve changes slope at this point (Fig. 3). The charger is located in the electrical/electronic equipment compartment on shelf E3-1. The charger should not be operated with the output shorted or without some load.
B. The charger operating modes are controlled by a wire loop. When the loop is closed, the charger operates in the normal mode; when the loop is open; the charger operates in the high temperature mode. Relay contacts or switches in the loop open when the battery case temperature is above 1150F, external power is applied, there is loss of TR3 input to battery bus, or (on AT ALL EXCEPT CN-RMI thru CN-RML; CA ALL EXCEPT B2501 thru B2503; IDO ALL EXCEPT 601; OI ALL EXCEPT G-BGTW thru G-BJBJ; ZD ALL EXCEPT G-AVRL thru G-BJCV) STANDBY POWER switch is set to BAT. A high battery voltage, which results from the battery being fully charged, causes the charger output to pulse. The limited pulse type charger will pulse for a limited time and then go into the high temperature-operating mode. The two modes of charger operation are described in the following paragraphs (Fig. 3):
(1)
The normal mode provides rapid charging of the battery. The charger output is illustrated by the triangular plot in Fig. 3. Above approximately 16-ampere current, the charger acts like a normal unregulated transformer-rectifier supply. When the battery has sufficient charge so that charging current goes below 16 amperes, the charger provides the battery with a pulse charge. The limited pulse type charger will pulse for 90 to 170 seconds. The internal mode control then switches the charger to the high temperature mode.
(2)
Charger output in the high temperature mode is considerably less than when in the normal mode. A nearly constant voltage is provided through a current range of 0 to 25 amperes.
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C. With the limited pulse type charger, momentary interruption of the input 3-phase voltage for more than 1 second causes the charger to pulse for 90 to 170 seconds and then switch to the high temperature mode.
D. When the battery switch is positioned to ON, battery bus relay R1 (Fig. 2) momentarily energizes through R2 to signal the battery charger. The battery charger now supplies the necessary output to maintain the battery at the new loads on the battery bus.
4. DC Indication
A. A dc ammeter and a voltmeter are located on the forward overhead panel (P5). The ammeter operates in conjunction with special shunts in the output circuits of the three T-R units. The battery ground uses a critical length wire (0.001-ohm resistance nominal) which serves as a shunt for dc ammeter in the battery circuit. The ammeter may also be used to determine any current drain on the battery and to observe the performance of the battery charger. The dc voltmeter is used in conjunction with the same three wafer selector switch which enables voltages to be observed on dc buses No. 1, No. 2, and No. 3 or the output voltages of T-R units 1, 2, and 3 (Fig. 4). Positions on the selector switch on the forward overhead panel enable voltages to be observed on such buses as battery and hot battery. The seventh or TEST position on the selector switch obtains a positive dc connection through the M400 power system test module. This enables functional tests to be made using the dc indicators.
5. DC External Power
A. A dc external power receptacle permits connecting a 28-volt direct current ground supply to the battery circuit. The connection is made by inserting a three-pin plug into a mating receptacle located below the airplane battery on the control shield (J9) (Fig. 1). A placard is placed near the receptacle, which gives the procedure to be followed when connecting or disconnecting a dc external power supply. With the dc supply properly connected to the external power plug pins, the storage battery may remain connected or removed during application of external power. A circuit breaker is provided in the positive line to the receptacle to be used as called for on placard. 中国航空网 www.aero.cn 航空翻译 www.aviation.cn 本文链接地址：737 AMM 飞机维护手册 电源 ELECTRICAL POWER(49)
