A SERVICE OF

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60
PRELIMINARY
2 Theory of Operation (continued)
2.12 Fan Control Circuit
Located on NH-SYS-M board (System MCU and Control Circuit)
Located on NH-SYS-P board (Auxiliary Power for System, Detect Circuit for Voltage and Current)
Located on NH-SYS-S or NH-SYS-SA board (Driver Circuit for Bypass SCR)
-
7
+
14
1
2
3
UM12A
4081
4 13
UM8D
ULN2003A
5 12
UM8E
ULN2003A
RM1 6 1
5VS
FAN _A
FAN _O N
RM162
+12VS
FAN_SP EED_A
5
6
4
UM12B
4081
6 11
UM8F
ULN2003A
7 10
UM8G
ULN2003A
RM166
5VS
FAN _O N
RM167
+12VS
FAN_SP EED_B
DM34
DM32
RM163
FAN _L OCK_ A
FANLOCK_A
5VS
DM33
RM164
FANLOCK_B FAN_ LO CK _B
5VS
CM1 2 4
G1
G1
8
9
10
UM12C
4081
RM168
CM127
G1
5VS
(19)
(143)
(48)
1 16
9 8
UM8A
+12VS
CM123
G1
(17)
FAN - C
FAN - SP E ED-C
G1
RM6
10K
RM7
10K
5VS
CM1 3 6
104
G1
FANLOCK_C
(18)
FAN _SP E ED _C
FANLOCK_C
1
2
3
CNP 16
G1
CP 9 6
+12VS
DP5
G1
D
G
S
QP14
RP194
DP6
TO FAN
1
2
3
CNS A4
G1
CSA 16
+12VS
FAN_LOCK_A
DSA10
FAN _SP E ED _A
G1
D
G
S
QSA9
RSA 21
1
2
3
CNS A5
G1
CSA 17
+12VS
FAN _L OCK_ B
DSA11
FAN_SPEED_B
G1
D
G
S
QSA8
RSA 22
(a) Fan C is located at the rear panel of the power module’s input EMI fi lter. Fan A and Fan B are both located at the heat-sink for bypass SCR.
(b) MCU controls fan C via FAN-C (17).
(c) MCU detects a fan C failure via (18).
(d) When in bypass mode, FAN_A (143) will be high to control fan A; fan B will be off. If fan A experiences a failure, fan B will turn on.
(e) MCU detects a fan A failure via FANLOCK_A (19).
(f) MCU detects a fan B failure via FANLOCK_B (48).