Power Transformer (T1); Circuit Breakers (Cb1/Cb2); Surge Suppressors (Ss1/Ss2) - HindlePower SCRF SERIES Operating And Service Instructions

b. Power Transformer (T1)
1. With the AC and DC circuit breakers open or "OFF", open the cabinet and carefully check the line
voltage across the line terminals (TB1-L1 and TB1-L2). Refer to Section III, 2, a, 1 on page 6 if no AC
voltage is indicated. Check the wiring connections to ascertain that unit has the proper primary tap
connections for the line voltage indicated. Turn on the AC circuit breaker (CB1). Check that the voltage at
the primary is the same as that of the line. If not, CB1 or the wiring between it and T1 is open. In this case
proceed with checks under Section III, 2, c, 1 below.
2. Using an AC voltmeter, check AC secondary voltage on the main transformer (T1). See Table B
below for expected voltage values. If secondary voltages are much less than indicated, then either T1 is at
fault or the power regulating devices (SCR1 or SCR2) are faulty.
TABLE B - SECONDARY VOLTAGE OF TRANSFORMER T1
NOTE: The "X" of Table B voltages should be measured as they terminate on the full-wave bridge
components. Where power rectifier fuses are employed in the larger power chargers (see custom diagrams
and parts list), these fuses should also be checked, and replaced if unserviceable.
c. Circuit Breakers (CB1/CB2)
1. AC Circuit Breaker (CB1): When an AC voltmeter of suitable range is connected between leads
L1-L2 and indicates line voltage, but does not indicate when connected to the output terminals of CB1 when
closed, the circuit breaker is probably defective. Deenergize the AC supply to the charger and remove the
leads to the circuit breaker. Use a voltohmmeter to check for continuity between the circuit breaker
terminals with breaker manually closed. Zero resistance should be indicated if the unit is operative. If unit
checks OK, check performance by measuring the AC voltage drop across each pole of the breaker. This
voltage should be under 0.1 volt when the load current is normal. If a higher voltage drop is found, replace
the breaker.
2. DC Circuit Breaker (CB2): When the DC circuit breaker is suspected of being inoperative or at
fault, a similar test to that made for the AC breaker will determine the operating condition of the breaker.
3. If the polarity protection diode (CR1) is shorted, the battery will discharge into CR1, which will
trip the DC circuit breaker (CB2). Check CR1 with an ohmmeter (both polarities) for a shorted condition
and replace if required.
d. Surge Suppressors (SS1/SS2)
1. The metal-oxide varistor (MOV) type of surge suppressor is used throughout these battery
chargers instead of the older selenium type. This is because of personnel safety. When a selenium device
fails and arcs or burns, very toxic selenium fumes are given off which are very poisonous, if inhaled. The
MOV-type has a much sharper limiting "knee" characteristic and performs a better protection function. If an
MOV surge suppressor fails during a high-energy transient, it may explode. This is an obvious failure and
the part must be replaced.
2. If the suppressor is shorted, an ohmmeter check will indicate continuity. When the suppressor
shows an infinite resistance in both directions measured with it disconnected from the charger and has a
normal appearance it can be presumed to be in good operating condition.
Expected Voltages (AC)
Approximately 2 times float voltage
120 Vac
Leads or Locations
X1 to X5
Y1 to Y2
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