ALARM AND PROTECTION SCHEME
The basic controls circuits are protected with suitably rated SWITCH/MCB/MCCB & fuses to protect the controller section, relay module power supplies, aux. AC supply and annunciation.

The fault sensing circuits are AC supplies trouble, charger over current, charger failure, DC output under & over voltage, DC earth fault and battery over & under voltage etc.

The Alarm Module is an electronic circuitry with LED lamps/ facia and alarms, with separate TEST, ACCEPT & RESET push buttons. On occurrence of a fault that particular lamp will glow with sound of “BUZZER” and when “ACCEPT” button is pressed, it only stop the sound of “BUZZER” but the respective lamp still will be in glow mode. The lamp remains glowing until “RESET” push button is pressed. If the fault is already cleared, the lamp goes off but glows again if the fault persists.

Potential free “NO” contact common to all faults is provided for remote annunciation for customers use.

AC SUPPLY TROUBLE (ACSTR)
These consist of sensing circuits, which sense the input, supply voltage and OPAMP comparator circuits at the input of which the input supply voltage, after being suitably scaled down or up, are compared with a preset stable reference voltage. When the AC input supply voltage becomes lower or higher than the preset minimum or maximum level the comparator output switches thus energizing the relay or when phase failure occurs the comparator output switches thus de-energizing the relay. The relay activates the audio/visual annunciation circuit for fault monitoring.

CHARGER OVER CURRENT RELAY
The charger is provided with DC over current relay driver circuit which trips charger AC contactor when the load current exceeds the preset value. In this control circuit high gain op-amp comparator circuits are provided for over load protection of the chargers. The load current is compared with the input of the comparator and a stable preset maximum level of current. The output of the comparator drives the over current relays thru’ timer circuits to introduce time delay for relay actuation to prevent tripping due to momentary over load. Separate push buttons are provided for re-setting the relay once the fault is acknowledged. Relay contacts are also interlocked with the audio/visual annunciation circuit for fault monitoring and remote annunciations. This circuit will only operate if the current limiting circuit in the main controller fails to operate.

CHARGER CURRENT LIMIT RELAY
The chargers are providing with current limit relay, which gives audio-visual annunciation when the load current exceeds the normal rated value. In this control circuit high gain opamp comparator circuit are provided. The load current is compared at the input of the comparator with a stable preset reference. The output of the comparator drives the current limit relays. Due to incorporation of inner current loop by which the output voltage drops as the rated load is increased, thereby automatically transferring the load to the battery in order to avoid the overloading of the charger. This part functions only when the system is in constant voltage mode. In this charger current limit relay set at predefined value. Relay contacts are interlocked with the audio/visual annunciation circuit for fault monitoring.

CHARGER UNDER VOLTAGE RELAY
This consists of high gain op-amp comparator circuit at the input of which the charger output voltage, after being suitably scaled down, is compared with a stable preset reference. When the charger output voltage does not appear or becomes lower than the preset minimum level voltage. The comparator output switches after a fixed time delay to avoid false tripping thereby energies the charger under voltage relay. Relay contracts are interlocked with the audiovisual annunciation circuits for fault monitoring.

FUSE FAIL MODULES
Each fuse fail module consists of a low ampere (300mA) trip fuse in parallel with the main power fuse. In the event of the failure of the main fuse, this fuse also blows with a lever coming out and actuating the micro switch, which operates a relay for annunciation circuit. On occurrence of a fuse failure, both the main fuse as well as its corresponding trip-indicating fuse needs to be replaced.

DC FAIL RELAY
This consists of a relay connected at load bus end. At normal condition the relay actuates and when the output DC voltage at the load terminal becomes lower a certain set value, the relay de-energized. Relay contacts are interlocked with the audio-visual annunciation circuit for fault monitoring.

AVR DEFECTIVE RELAY
The charger is provided with AVR/ACR defective relay which indicates the power supply fail on AVR circuit. This relay get power 24V DC from on control system power supply section of AVR. Normally this relay always energized and only de-energized when power supply section of AVR is not working. Relay contacts are also interlocked with the audio/visual annunciation circuit for fault monitoring.

DETAILS OF TEMPERATURE COMPENSATION MODULE
Temperature compensation of VRLA is essential to save the battery life. At increasing ambient temperature battery trickle/floating voltage should be decreased and at decreasing ambient temp. Battery float/trickle voltage needs to increase and it has a specified limiting pattern (generally supplied by the manufacturer). This temperature compensator has dual functions – one part sense the battery temperature directly from battery terminals (provision for 5 nos. battery) and convert them to an average value of control voltage signal – Finally this control voltage applied to the precision op.amp. – having summing / multiplying and limiting function. The resultant analog output finally sends to converter voltage reference terminal for automatic temperature compensated voltage tracking.

The other parts of the system are continuously monitoring battery temperature from the same terminal – but other set of similar high precision temperature sensor. The actual sensing voltage is fed to the amplifier and comparator circuit with a present reference value. Exceeding temperature the sensor will deliver proportional higher signal voltage to the comparator input. If this values higher than present reference, the voltage comparator output changes the state – immediately the appropriate over temperature fault LED will glow and a summing remote fault relay are activate, the potential free NO/NC contact terminals are available for user alarm system from this relay.

DC UNDER/OVER VOLTAGE RELAY
These consist of sensing circuit which senses the output DC voltage at the load terminal, after being suitably scaled down and is compared with the stable preset reference. When this voltage goes lower or higher than the stable preset level, the under or over voltage relay actuates. Relay contacts are interlocked with the audio-visual annunciation circuit for fault monitoring at remote terminals.

DC under voltage can occur in case of power failure and charger failure.

DC over voltage will occur only if the controller circuit becomes faulty or if the filter capacitor fuse fails imposing a high ripple voltage above set voltage at the output.

DC EARTH FAULT RELAY
This consists of relay, which senses the leakage current from (either) bus and ground.
The center point of the BATTERY bus is connected thru a resistance voltage divider circuit to the earth fault relay control circuit, which is also earthed. When any leakage path develops in either DC bus, the same leakage current will flow thru this circuit and if it exceeds around 5 mA the earth leakage relay actuates and is interlocked with audio/visual annunciation circuit.

FLOAT / BOOST CHANGEOVER RELAY
This electronic circuit ensures automatic boost charging of the battery (after discharge) when the AC supply is restored. The relay circuits drive its DC supply from the battery bank and the battery voltage is compared with a suitable reference at the input of the high gain comparator. When the battery voltage reaches below set voltage during discharge, the relay actuate with a time delay thru' switching of the comparator such that the boost charging starts automatically with the restoration of input supply and the charging continues at the pre-adjusted rate. When the battery voltage reaches around set voltage the float/boost relay de-energized, transfer/connect the battery to the float bus and float charging continues in the usual manner.

CHARGER FAIL
This consists of high gain op-amp comparator circuit at the input of which the charger output voltage, after being suitably scaled down, is compared with a stable preset reference. When the charger output voltage does not appear or becomes lower than the preset minimum level the comparator output switches after a fixed time delay to avoid false tripping, thereby energizing the charger fail relay. Relay contact is interlocked with the audio/visual annunciation circuit for fault monitoring & to give some back-up power to load.

BLOCKING DIODE FAIL RELAY MODULE
The charger is provided with blocking diode relay, which only use for indication when the blocking diode fails. In this control circuit high gain op-amp comparator circuit is provided for open or short of the blocking diode. The above condition is compared at the input of the comparator with a stable preset reference. The output of the comparator drives the blocking diode fail relay. One AC contactor N/O contact is provided for avoid false peak up the relay. Relay contact is also interlocked with the visual indication circuit for fault monitoring.

BOOST CHARGER UNDER VOLTAGE RELAY
This consists of high gain op-amp comparator circuit at the input of which the BOOST charger output voltage, after being suitably scaled down, is compared with a stable preset reference. When the charger output voltage does not appear or becomes lower than the preset minimum level voltage. The comparator output switches after a fixed time delay to avoid false tripping thereby energies the charger under voltage relay. Relay contracts are interlocked with the audiovisual annunciation circuits for fault monitoring.

BOOST CHARGER OVER VOLTAGE RELAY
This consists of high gain op-amp comparator circuit at the input of which the BOOST charger output voltage, after being suitably scaled down, is compared with a stable preset reference. When the charger output voltage becomes HIGHER than the preset maximum level voltage. The comparator output switches after a fixed time delay to avoid false tripping thereby energize the charger over voltage relay. Relay contracts are interlocked with the audiovisual annunciation circuits for fault monitoring.

BATTERY UNDER VOLTAGE RELAYS
This consists of sensing circuit which senses the battery terminal voltage and are compare with a stable preset reference. When this voltage goes lower than the preset minimum level the under voltage relays will actuate which are interlocked with the charger. The relay contacts are also interlocked with the visual annunciation circuit for fault monitoring.

BATTERY OVER VOLTAGE RELAYS
This consists of sensing circuit which senses the battery terminal voltage and compare with a stable preset reference. When this voltage goes above than the preset maximum level the over voltage relays will actuate which are interlocked with the charger. The relay contacts are also interlocked with the visual annunciation circuit for fault monitoring.

BATTERY ON LOAD RELAY
This electronic circuit ensures the battery discharge condition. This incorporates a time delay feature to prevent wronged signal of the relays during short current discharge as often happens during float charging operations due to the closing or tripping operation of circuit breakers. The relay circuits drive its DC supply from the battery bank and the battery signal is compared with a suitable reference at the input of the high gain comparator. When the battery signal reaches in stable condition during discharge, the relay actuate with a time delay thru' switching of the comparator. The relay contacts are also interlocked with the annunciation circuit for fault monitoring.

BATTERY DEEP DISCHARGE RELAYS
This consists of sensing circuit which senses the battery terminal voltage, after being suitably scaled down and are compared with a stable preset reference. When the battery voltage goes lower than the preset minimum level the deep discharge relays will actuate which are interlocked with the charger. DC contactors is isolated automatically the load bus and the battery bank. This helps to protect the battery in long life application. The relay contacts are also interlocked with the visual annunciation circuit for fault monitoring.

BATTERY CHARGED RELAY
This electronic circuit ensures automatic boost charging of the battery (after discharge) when the AC supply is restored. The relay contacts are interlocked as per the interlocking schedule.

The relay circuits drive the DC supply from the battery bank and the battery voltage is compared with a suitable reference at the input of the high gain comparator. When the battery voltage reaches around at predefined set value the battery charged relay energizes, transferring the battery to the float bus and float charging continues in the usual manner.

BATTERY ON DISCHARGE RELAY
This electronic circuit ensures the battery discharge condition. This incorporates a time delay feature to prevent wrong signal of the relays during short current discharge as often happens during float charging operations due to the closing or tripping operation of circuit breakers. The relay circuits drive its DC supply from the battery bank and the battery signal is compared with a suitable reference at the input of the high gain comparator. When the battery signal reaches in stable condition during discharge, the relay actuate with a time delay thru' switching of the comparator. The relay contacts are also interlocked with the visual annunciation circuit for fault monitoring.

START / FINISH RELAY
The rate of charging is automatically monitored by sensing the battery voltage. The battery voltage is fed to a SCR latching circuit thru’ a potentiometer for actuating the start/finish relay for changing the reference of the boost charger controller from starting to finishing rate of charging. The potentiometer is connected to the gate of the SCR with Zener diode in series for adjusting the triggering voltage of the SCR.

TRICKLE CHARGING MONITORING RELAY
This electronic circuit ensures battery trickle charging current at the time of float charging. To measure the trickle charging current, the shunt signal collect from battery charge/discharge monitoring meter is properly filtered and protect from high current signal and one directional path to prevent the trickle charging monitoring meter from high boost charging current or battery discharge current. Then the output filtered signal is fed into a high gain shunt amplifier circuit. Finally the output of the amplifier circuit is fed to trickle charging monitoring meter thru’ a push button. To measure the trickle charging
current, press the push button, trickle charging current is directly shows at trickle current monitoring meter. Never press the trickle current check push button at the time of battery charging or in battery discharging condition. This precaution is to take care for long life of the relay module.

OVER CURRENT RELAY FOR REGENERATIVE DISCHARGER
The charger have a provision of over current relay in discharge mode, which trips charger DC contactor when the discharge current exceeds from the normal rated value. In this control circuit high gain op-amp comparator circuit is provided for over current protection of the charger. The over current is compared at the input of the comparator with a stable preset reference. The output of the comparator drives the over current relay thru' timer circuit to introduce time delay for relay actuation to prevent tripping due to Momentary over load. Separate push button is provided for re-setting the relay once the fault is acknowledged. Relay contact is also interlocked with the visual annunciation circuit for fault monitoring.

One no. CTD and one no. VTD are provided in the input circuit of each incomer to collect current signals of the output current and voltage for customer uses.

For regenerative mode of operation, select the regenerative mode thru’ regenerative mode selector switch is providing in side the panel. Regenerative mode on switch, indicating lamps for regenerative mode on and over current at regenerative mode is provide for operation, protection and observation. An amp-hour meter is providing for measuring the total discharge power of battery. A DC contactor is provide for connecting the battery reverse connection with the charger at the time of discharging mode.

DROPPER DIODE SELECTION RELAY
These consist of sensing circuit which senses the output DC voltage at the load terminal, after being suitably scaled down and is compared with the stable preset reference. When this voltage goes lower or higher than the stable preset level, the upper or lower voltage relay actuates. Relay contacts are interlocked with the DC contactor circuit for dropper diode selection.

AUTO EQUALIZING RELAY:
Auto equalizing charging facilities are provided in this system. The purpose of equalizing charge is to bring the cells in a battery bank in step, since they tend to fall out of step during prolonged float charging operation.

Auto equalizing relay card is meant for automatic equalizing charging of the battery bank (recommended half rate of charging current), when the battery draws a current more than a specified value continuously during floating operation. The electronic control card basically consists of a shunt amplifier, which constantly monitors the battery trickle charging current by amplifying the signal derived from the ammeter shunt in series with the battery. The amplified signal is compared with a stable reference at the input of a high gain comparator and when it exceeds the preset reference for more than 30 Sec. the output switches, thereby actuating the auto equalizing relay which is suitably interlocked to switch the float cum boost charger in equalizing mode of Charging, as per selection of the switch. The battery voltage is also compared with a stable reference at the input of another comparator. When the battery voltage on charge reaches around set value, it switches off the relay after a pre-adjusted time delay and the battery is again transferred to the float-charging mode and trickle charging continues in the usual manner.

CTD AND VTD
VTD’s and CTD’s are provide across the all voltmeters and ammeters excluding charge/discharge ammeter to collect current signals for customer uses.