TM 9-6115-668-13
1.13.3 Maintenance Free Battery Set Assembly.
The battery set consists of 12-volt batteries 2G1 and 2G2, connected in series. It provides power for the
diesel engine glow plugs and starter, and for the 24-V power circuits in the engine preheat assembly and
switching system. Since battery capacity is one of the factors determining the cold-starting ability of a
diesel engine, at temperatures below about 19.4 °F (-7 “C) the onboard battery set is connected in paral-
lel to an external battery set through the J3 SLAVE RECEPTACLE 24 VOLTS.
1.13.4 Starter.
The 1M1 starter, flange-mounted on the diesel engine, is an electromagnetically actuated DC series-
characteristic motor. During starting, it turns the diesel engine until the engine can run on its own.
1.13.5 Battery Charging Alternator.
The 1G3 battery charging alternator, flange-mounted on the diesel engine, is a self-excited synchronous
generator with a threephase current rectifier and a generator regulator N6. It charges battery set 2G1 and
2G2 via shunt R11. N6 limits charging voltage when the battery set is charged, and charging current
when it is discharged. Charging current is displayed on the BATTERY CHARGE meter (P7). If the battery
set is not being charged during operation, the BATTERY CHARGING CONTROL lamp (H2) will light up.
1.13.6 Engine Preheating Assembly.
The engine preheating assembly consists of a heating unit with fan, an air/oil heat exchanger, an electric
oil pump, and an air guide system with air flap. Air heated by the heating unit is blown through the air/oil
heat exchanger connected to the engine oil circuit. Cold engine oil is drawn up from the sump and moni-
tored by temperature switch S103/S104. Engine oil heated in the air/oil heat exchanger is pumped back
to the engine by the electric oil pump. A portion of the heated air is blown through an air flap onto the fuel
injection pump and engine cylinder heads. Another portion of the heated air is blown onto the generator
1G3 belts.
1.13.7 Synchronous Generator Assembly.
The synchronous generator is a 400-Hz generator with an apparent output of 187.5 kVA and a rated
power factor of 0.8. It consists of the exciter (external pole generator), a rotating rectifier, and the actual
generator (internal pole generator). Voltage regulator N2 prepares and regulates exciter voltage in order
to regulate the output voltage. N2 consists of the Equal Power Distribution, Linear Regulator, Averaging
Circuit, and Voltage Sensing Transformer boards.
The current-proportional voltage tapped at T11/R12, T12/R13, and T13/R14 is transformed by a voltage
sensing transformer to values that can be processed by the averaging circuit. The reason for the averag-
ing circuit is that the sensed voltage can be overlain by interference pulses that falsify the readings. The
linear regulator generates exciter output for the synchronous generator (or generators, in parallel opera-
tion).
The equal power distribution circuit detects the reactive power component of the current based on the
current-proportional voltage tapped at T1/R15. Without reactive power compensation, synchronous gen-
erators operated in parallel would experience different loads. The outcome of this process affects the ex-
citer voltage of the linear regulator.
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