King Air C90GTi, Pilot Training Manual

Page: 63 / 557

S t a r t e r p owe r t o e a c h i n d iv i d u a l s t a r t e r /
generator is provided by the batter y, or by
the operating generator for cross-starts. The
star t cycle is controlled by a three-position
s w i t c h , o n e f o r e a c h e n g i n e , p l a c a r d e d :
I G N I T I O N A N D E N G I N E S TA RT –
LEFT–RIGHT–ON–OFF STARTER ONLY,
l o c a t e d o n t h e p i l o t ’s l e f t s u b - p a n e l
(Figure 2-3).
S e l e c t i n g a s t a r t s w i t c h t o e i t h e r t h e
S TA RT E R o n ly p o s i t i o n o r O N a c t iva t e s
the star ter and disables the respective gen-
erator. The star ter drives the compressor
section of the engine through the accessor y
gearbox.
D u r i n g e n g i n e s t a r t s , t h e b a t t e r y i s c o n -
nected to the starter/generator by the starter
relay. With one engine r unning and its gen-
erator on the line, the opposite engine can
by star ted with power from the batter y and
operating generator through the starter relay
a n d t h e c r o s s - s t a r t r e l ay. T h i s i s c a l l e d a
cross-star t. Nor mally one engine is star ted
on batter y power alone, and the second en-
gine is cross-star ted.
During a cross generator start, (Figure 2-15)
the operating generator control panel closes
the cross-start relay, bypassing the genera-
tor bus, current limiter and bus tie relay. This
assures the 250-amp cur rent limiter will not
open due to transient surges, since the gen-
erator would nor mally provide the cur rent
required for the star t. In addition, while a
starter is selected the bus tie sensors are dis-
abled to prevent them from opening their
respective bus tie relays.
Do not exceed the starter motor op-
erating time limits of 40 seconds
ON, 1 minute off, 40 seconds ON,
1 minute off, 40 seconds ON, then
30 minutes off.
DC GENERATION
T h e g e n e r a t o r p h a s e o f o p e r a t i o n i s c o n -
trolled by the generator switches, located in
th e p ilo t’s left su b p an el, n ex t to th e BAT
switch under the MASTER SWITCH gang
bar (Figure 2-3). The switches provide OFF,
ON, and RESET capabilities. The generat-
ing system is self-exciting and does not re-
q u i r e e l e c t r i c a l p owe r f r o m t h e a i r c r a f t
electrical system for operation.
Generator operation is controlled through
two generator control units (GCU) mounted
below the center aisle floor, that make con-
stant voltage available to the buses during
va r i a t i o n s i n e n g i n e s p e e d a n d e l e c t r i c a l
load requirements. The generators are man-
ually connected to the GCUs by GEN 1 and
GEN 2 control switches located on the pilot’s
left subpanel. The load on each generator is
indicated by the respective left and right
loadmeters located on the overhead panel
(Figure 2-4).
The generator control units are designed to
control the generators and the load shared
within 2.5 percent.
The generator control units (GCU) provide
the following functions:
• Voltage regulation and line contactor
control
• Over voltage and overexcitation pro-
tection
• Paralleling/load sharing
• Reverse-cur rent protection
• Cross-star t relay activation
Voltage Regulation and Line
Contactor Control
The generators are nor mally regulated to
28.25 ±.25 VDC. When the generator con-
t r o l sw i t c h i s h e l d t o R E S E T, g e n e r a t o r
residual voltage is applied through the GCU
to the generator shunt f ield causing the gen-
erator output voltage to rise. This switch
should be held in the RESET position for
CAUTION
KING AIR C90GTi/C90GTx PILOT TRAINING MANUAL
2-14
FOR TRAINING PURPOSES ONLY
2
ELECTRIC
AL
POWER
SY
STEMS