Alarm and Battery Disconnect Relays, Fuse, Status LED

Alarm and Battery Disconnect Relays

Two relays support Power Supply operation:

•Alarm relay

•Battery disconnect relay

ALARM RELAY AND ALARM SIGNAL

The Alarm relay is provided for customer use. In normal operation the contact alarm relay is open. If an AC power failure occurs and the unit defaults to the battery backup, the relay will cycle open/closed once per second (that is one second open then one second closed). The tolerance on this cycle time is 25 percent.

This indicates the battery is discharging in support of the load. If battery voltage decreases to 45V the relay stays closed to indicate the battery is becoming depleted. The relay will open automatically when normal AC voltage is restored. Table 1 summarizes alarm relay operation.

Table 1. Alarm Relay Operation

	Condition	Alarm Relay

	Normal	Open

	AC Power Failure/Battery	Cycles open/closed once
	Backup engaged	per second

	Battery voltage is less than	Stays closed
	40V	Stays closed
	40V

An alarm signal that cycles synchronously with the alarm relay is provided on the output cable. This signal, which is open during normal operation, cycles between open and ground during battery backup

(as described for the alarm relay), and is ground when the battery voltage falls below 45V.

BATTERY FAIL ALARM

For battery backup systems that employ the optional Battery Test Assembly (P/N 1175044L3) an alarm signal is provided to the TA 750/850 L2 Power Supply that indicates a failed battery (in need of immediate replacement). This signal is passed to the Alarm Relay and Output Alarm Signal. When a failed battery is detected, it is indicated by the Alarm Relay cycling open for 450 ms, then closed for 450 ms. Battery failure is also indicated by the output alarm signal cycling open to ground at the same rate.

BATTERY DISCONNECT RELAY

The battery disconnect relay disconnects the battery pack from the system if the battery voltage falls below 40 VDC. This feature prevents damage to the

batteries. The batteries will be recharged when normal AC voltage is restored and the relay will close when the battery voltage exceeds 40V.

Certain alarm features on the power supply are still powered by the battery after the disconnect relay is opened. These features slowly drain the battery. If it is known that AC power will be unavailable for an extended period (greater than a week), ADTRAN recommends that the battery be disconnected from the power supply to prevent over-discharge.

The batteries used in ADTRAN’s battery backup system are designed to withstand occasional over-discharge. While it is not recommended, the batteries can recover their full capacity under normal charging conditions, even when they have been subjected to extreme over-discharge.

Fuse

A 3-amp fuse on the back panel protects the unit from over current. The fuse isolates the AC input from the power supply in the event of a fault. The fuse is replaced by twisting the black cap to the left and pulling the fuse out. After the new fuse is inserted, the cap is pushed back in and turned to the right.

Status LED

Asingle multi-feature LED on the front panel provides AC operation or battery operation power status. Refer to Table 2 for indication descriptions.

Table 2. LED Indication

AC Power		Battery
Operation		Operation

Green	OK	Green	OK (charging)

Yellow	Power Fail	Yellow	Discharging

Red	Power Fail	Red	Low (<40V)

Off	Power Fail	Off	Disconnected

3. INSTALLATION

C A U T I O N !

SUBJECT TO ELECTROSTATIC DAMAGE

OR DECREASE IN RELIABILITY.

HANDLING PRECAUTIONS REQUIRED.

After unpacking the unit, inspect it for damage. If damage is noted, file a claim with the carrier then notify ADTRAN Customer Service.

Section 61175043L2-5, Issue 1

61175043L2-5A