SBS AT10.1 SERIES, Operating And Service Instructions

Page: 62 / 104

SERVICING THE AT10.1
56
SYMPTOM
PROBABLE
CAUSE
RECOMMENDED ACTION
LOW DC
VOLTAGE
indicator is on
ac & dc
breakers are
closed
ac input
voltage is
normal
dc output
current is
present
1. Battery is
discharged
2. Low DCV
alarm and Float
voltage settings
are mismatched
3. Defective
SCR module
4. Defective
Main Control
PC Board (A1)
5. Defective dc
output circuit
breaker (CB2)
1. After an ac power failure, or battery discharge for any other
reason, it may take several hours to recharge the battery. It is
normal for the
LOW DC VOLTAGE indicator to be on until the
battery voltage is above the Low DC Voltage alarm setting.
2. Make sure the Low DC Voltage alarm setting is lower than
the Float voltage setting. See Sections 2.3.2 and 2.3.4 for
details.
3. Use a clamp-on ammeter to measure current in wires #
5
and # 6 , between the transformer (T1) and SCRs (Q1/Q2). If it
is less than 50% of the dc output current, one of the SCRs is
defective. Replace SCR modules (Q1/Q2) as needed.
4. Turn off (open) both front panel circuit breakers, or lock out
ac and dc power externally if the AT10.1 has fuses only. Wait
60 seconds. Restart by restoring dc power
first , followed by
ac power second. If the AT10.1 output voltage is normal, but
the
LOW DC VOLTAGE indicator is still on, replace the Main
Control PC Board (A1).
5. Shut down the AT10.1 and disconnect the battery. Connect
a light dc load to the AT10.1 and turn on (close) the dc circuit
breaker (CB2). Measure the dc voltage across TB1(+) and
TB1(-). If no voltage is measured, replace the dc output circuit
breaker (CB2).
DC OUTPUT
FAILURE
indicator is on
ac & dc
breakers
(CB1/CB2)
are closed
ac input
voltage is
normal
1. Defective
SCR module
2. Defective
Main Control
PC Board (A1)
3. Defective
transformer
(T1)
4. Defective dc
output circuit
breaker (CB2)
1. Use a clamp-on ammeter to measure current in wires # 5
and # 6 , between the transformer (T1) and SCRs (Q1/Q2). If it
is less than 50% of the dc output current, one of the SCRs is
defective. Replace SCR modules (Q1/Q2) as needed.
2. Turn off (open) both front panel breakers, or lock out ac and
dc power externally if the AT10.1 has fuses only. Wait 60
seconds. Restart by restoring dc power
first , followed by ac
power second. If the AT10.1 output voltage and current are
normal, but the
DC OUTPUT FAILURE indicator is still on,
replace the Main Control PC Board (A1).
3. Use an ac voltmeter to measure the secondary potential
from T1-X1 to X5. It is normally 50% to 80% higher than the
rated dc output voltage. If it is too low, check the
primary tap
wiring. See Section 1.6 for details. If the primary (T1-H#)
voltage is 0 Vac, replace the main power transformer (T1).
4. Shut down the AT10.1 and disconnect the battery. Connect
a light dc load to the AT10.1 and turn on (close) the dc circuit
breaker (CB2). Measure the dc voltage across TB1(+) and
TB1(-). If no voltage is measured, replace the dc output circuit
breaker (CB2).
AC INPUT
FAILURE
indicator is on
1. AC power
failure
2. Tripped
upstream feed
breaker / fuse
1. If the ac input power fails, the front panel AC ON indicator
goes out, and the AC INPUT FAILURE indicator goes on.
2. Make sure the front panel ac input circuit breaker (CB1) is
closed. Measure ac voltage at TB1-L1 to TB1-L2. If it is zero
(Vac), check upstream ac distribution breakers and/or fuses.