Exide Technologies Section 93.30 - Manual (Page 11)

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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 line terminals on TB1, terminals (L1 to L2, L2 to L3 & L3 to L1). If no AC voltage is indicated, refer to
Section III, 3, a, 1. Check the wiring connections to ascertain that the 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 this is not the case, CB1 or the wiring between it and T1 is open. In this case, proceed with checks
under Section III, 3, c, 1.
2. Check AC secondary voltage on T1 (see Table B below for expected voltage values). If secondary voltages
are much less than indicated or not balanced, then either T1 is at fault or the power regulating devices (SCR1, SCR2
or SCR3) are faulty.
TABLE B - SECONDARY VOLTAGE OF TRANSFORMER T1
Expected Voltages (AC) Leads or Locations
Approximately equal to float voltage X1 to X2, X2 to X3 and X3 to X1
120 Vac Y1 to Y2, Y2 to Y3 and Y3 to Y1
Note: The "X" of Table B voltages should be measured as they terminate on the full-wave bridge
components. All other voltages may be measured at the end of the transformer leads. 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, L2-
L3 & L3-L1 and indicates line voltage, but does not indicate when connected to the output terminals of CB1 when
closed, the circuit breaker is probably defective. De-energize the AC supply to the charger and remove the leads to the
circuit breaker. Use a volt-ohmmeter 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/SS3/SS4)
1. The metal-oxide varistor (MOV) type of surge suppressor is used throughout these battery chargers instead
of the older selenium type. This is done for personnel safety. When a selenium device fails and arcs or burns, 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.
e. Rectifier Diodes (CR4/CR5/CR6) - also see Section III, 3, f
1. In lower current three phase chargers, these diodes are part of an SCR-diode module, in which the SCR and
diode of each leg are contained in an assembly mounted on an electrically insulated heatsink plate. Three connections
(plus one SCR gate terminal) are available for checking. In higher current three phase chargers, individual diodes and
SCRs are used instead of modules. Check the diode portion of each bridge leg by disconnecting one terminal and
measuring the forward and reverse resistance in either of two ways:
a) Using an ohmmeter, use the Rx1 scale for the forward resistance. This should show approximately 5 to
10 ohms. The reverse resistance should be up in the thousands of ohms (probably 50,000 or more) measured with a
higher scale of the meter.
b) Connect the diodes in series with a 6 or 12-volt lamp across a DC source of the same voltage. The lamp
must require at least one-quarter Ampere. The lamp should light with nearly full brilliance with current flowing in the
forward direction and not at all in reverse. If it lights in both directions, the diode is shorted. If in neither direction, the
diode is open.