MD Helicopters 369-500, Maintenance Instructions Manual

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CSP-HMI-3
MD Helicopters, Inc
.
MAINTENANCE MANUAL
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[ HMI − 3 Book TOC ]
[ Chapter 96 TOC ]
96-10-00
Page 201
TR16-001
The information disclosed herein is proprietary to MD Helicopters, Inc.
Neither this document nor any part hereof may be reproduced or transferred to
other documents or used or disclosed to others for manufacturing or any other
purpose except as specifically authorized in writing by MD Helicopters, Inc.
Copyright
©
1999 − 2016 by MD Helicopters, Inc.
DC GENERATION
MAINTENANCE PRACTICES
1. Description and Operation
Voltage generation, regulation and power
control equipment consists of a nicad battery,
starter/generator, voltage and current regula­
tion and control components, circuit breakers,
control switches and associated components. A
voltage regulator, overvoltage relay and
reverse current relay function with the
starter/generator to monitor, regulate and
control dc output voltage (nominal 28 Vdc),
battery charging and protect components and
circuits from overvoltages. The starter/genera­
tor both starts the engine and generates dc
electrical power.
NOTE:
D
On 369E helicopters S/N 384 & subs,
369FF helicopters S/N 076 & subs, 500N
helicopters S/N 001 & subs and 600N he­
licopters S/N 003 & subs, a generator con­
trol unit GCU replaces voltage regulator
(VR1), (K300) and (K103) providing for
regulation, reverse current, overcurrent
and overvoltage protection.
D
On 369E helicopters S/N 509 & subs,
369FF helicopters S/N 092 & subs, 500N
helicopters S/N 045 & subs and 600N he­
licopters S/N 003 & subs, a new GCU is
installed that eliminates the squat
switch. Reference applicable wiring dia­
gram.
(1). The voltage regulator, at engine speeds
of idle rpm and greater, monitors and
maintains correct generator output
voltage by varying generator field
current. The overvoltage relay, when
energized by an overvoltage sensed by
the voltage regulator, opens a switch
circuit of the reverse current relay
removing generator output voltage from
the main dc power bus. The reverse
current relay prevents discharging of
battery through generator circuits
when generator output voltage is less
than battery voltage. Voltage genera­
tion and regulation circuits are con­
trolled by the GEN-OFF switch and
function with the switch at GEN. If
generator output voltage is absent or
excessively low, the reverse current
relay senses same and causes a GEN
OUT
lamp on the instrument panel to
illuminate.
NOTE:
On 369E helicopters S/N 384 & subs,
369FF helicopters S/N 076 & subs, 500N he­
licopters S/N 001 & subs and 600N helicop­
ters S/N 003 & subs, the GEN switch will
not enable the engine out warning and audi­
ble headset warning.
With GEN-OFF switch at GEN, a ground is
supplied to enable engine power out and
warning horn equipment that activates in
event of low engine or main rotor speed. A
15-ampere circuit breaker protects the
generator field circuit. During engine starting,
the voltage regulator opens the generator field
circuit when the START circuit is energized.
(2). 369E helicopters S/N 384 & subs,
369FF helicopters S/N 076 & subs,
500N helicopters S/N 001 & subs and
600N helicopters S/N 001 & subs:
The GCU regulates, at engine speeds of
idle rpm and greater, monitors and
maintains correct generator output
voltage by varying generator field
current. An overvoltage sensed by the
GCU trips the GEN
switch removing
power to the GCU and removing
generator output voltage from the main
dc power bus. The GCU reverse current
circuitry prevents discharging of
battery through generator circuits
when generator output voltage is less
than battery voltage. If generator
output voltage is absent or excessively
low, the reverse current circuit senses
same tripping the GEN
switch remov­
ing power to GCU and provides internal
ground to illuminate GEN OUT lamp
on the instrument panel.
2. DC Generation − Fault Isolation
Refer to Sec. 96-00-00 for information on
troubleshooting the start-generation system.