Ac Power Failure Alarm Relay (Ej0085) - HindlePower SCRF SERIES Operating And Service Instructions

2. AC POWER FAILURE ALARM RELAY (EJ0085) - WITH OPTIONAL INDICATOR LIGHT
Purpose: The purpose of this alarm is to notify the user that the AC input power to the battery charger
has been interrupted. A front panel "AC FAILURE" lamp is optional for local indication. Relay contacts are
provided for remote monitoring.
Description: The principle of operation utilizes the normally closed contacts of an AC relay (K1). K1 is
powered from the AC line at the primary of the transformer (T1). TM1, when energized, holds the normally
closed contacts open disabling the alarm indication. When the AC line fails or the AC circuit breaker (CB1)
is opened for any reason, the alarm contacts will close activating the alarm indicator. EJ0085 shows the
circuit with the optional panel indicator lamp and external relay connections for remote indication. The
indicator lamp must operate from the battery power since the AC line power is not available in an alarm
state. As a result, the indicator light operating voltage must match the battery DC voltage or must utilize a
series-dropping resistor to compensate for the difference in voltage between the battery and indicator lamp.
3. AC INPUT VOLTMETER (EJ0095/EJ0121) AND AMMETER (EJ0134/EJ0135) OPTIONS
Purpose: These options are to permit the user to monitor the input AC line voltage and line current to
the battery charger. This may be done for either single phase or three phase input power.
Descriptions:
a. Single phase AC:
connections to the AC ammeter. The ammeter is usually connected to the AC line via a current transformer
(CT1) if the line current is over 50 Amperes.
b. Three Phase AC: EJ0121 shows the connections to the ac voltmeter and EJ0135 and shows the
connections to the AC ammeter. Both show the connections utilizing a single meter, one to monitor the
three phase-to-phase voltages and one to monitor the three line currents. A two-pole, three position switch
(SW5) is used to switch the voltmeter from phase-to-phase to check all three input voltages. The ammeter
switch (SW6) is a special switch, which shorts all unused current transformer secondaries. Upon changing
switch position, it shorts the current transformer (CT1) secondary in use before transferring the ammeter to a
new position. This prevents very high voltage arcs when the secondary is open circuited.
CAUTION: NEVER OPERATE A CURRENT TRANSFORMER WITHOUT A SECONDARY
LOAD OR SHORT CIRCUIT ACROSS THE SECONDARY TERMINALS.
4. HIGH / LOW DC VOLTAGE ALARM RELAYS (EJ0083) - W/OPTIONAL INDICATOR LIGHTS
Purpose: The HIGH/LOW DC Voltage Alarm (HLVA) provides alarm indication for the DC system in
the event of a malfunction of the battery charger, which causes the battery voltage to rise or drop to a
dangerous level. Relay contacts and optional front panel lamps provide alarm indications.
Description: The HLVA printed circuit board consists of two independent operational amplifier circuits,
one monitoring the battery voltage for a high voltage condition and the other monitoring for a low voltage
condition.
The board obtains its operating voltage (12VDC) from the battery terminals and if required, an
externally mounted dropping resistor (R57).
There are two potentiometers on the HLVA PC board (A2). Viewed from the component side of the
board, the potentiometer near the top-left of the board is the LOW voltage alarm (LVA) threshold
adjustment. The right-hand potentiometer at the top of the board is the HIGH voltage alarm (HVA)
threshold adjustment.
EJ0095 shows the connections to the ac voltmeter and EJ0134 shows the
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