BCD.00617 Rev AB,16-Nov-2015

Page 8 of 15

MELCHER

The Power Partners.

Accessories Data Sheet

Backplanes BPD, BPF for T Series

Battery Selection

When selecting a battery, the following aspects should be

considered:

1. Batteries are normally specified at 20°C.

Steady operation at higher temperatures will shorten the life

time of a battery. For every 10 °C temperature increase the

battery lifetime is halved.

2. Worst case considerations with regard to the necessary

battery capacity should include operation at the lowest

possible temperature and highest possible discharge

current, since under such conditions a substantial capacity

drop has to be expected.

3. The capacity of a battery deteriorates with time. Therefore

decisions on battery capacity should be based upon 20%

ageing loss.

4. Consult the battery manufacturer for correct layout of the

battery system.

Selecting the Right Battery and Back Plane

Configuration

As mentioned in the T series data sheet the power factor

correction at the input of the T unit generates a ripple voltage at

the output of twice the input frequency, causing a ripple current

into the connected battery.

For most battery types the low frequency ripple current should

not exceed 5 A per 100 Ah (0.05 C). Some manufacturers (with

newer battery technology) specify 10 A per 100 Ah (0.1 C).

Excessive ripple current can increase the battery temperature

and reduces the battery lifetime. For a single phase system

additional output capacitors may be necessary depending

upon the selected battery type.

Note:

With

the

T units

symmetrically

connected

to

a

3-phase (Y) mains supply the low frequency output ripple is

virtually zero, only a high frequency ripple and noise of

<100 mVAC at the switching frequency of 65.5 kHz remains.

System Integration

Mains Input Voltage Monitoring

The T unit interprets a mains failure as a system error, indi-

cated by the red Error LED together with a System Good failure

signal. Should a dedicated mains failure identification be

required this signal would have to be established externally.

Available signals/signal combinations (Please also refer to

the T Series data sheet on our website):

The T unit provides two open collector signals, System Good

and Power Down.

The System Good signal monitors the operational function of

a single T unit. In case of reduced available output power due

to a mains failure, a T unit failure or inhibit, the signal changes

from low to high impedance.

In systems with battery back-up or with n+1 redundancy the

failure of one single unit does not cause a failure of the system

as the required output power is still available either from the

battery or from the remaining T units. To indicate the status of

the whole system, the System Good signals of all 3 units

should be connected in series on the back plane.

The System Good output can be combined with similar out-

puts of other DC-DC converters such as CQ units, integrating

the additional information into the overall system status

signal.

If only the system status of the T unit is to be monitored, Sys In

should be wired to Vo–.

The Power Down signal monitors the output voltage level of

the bus bar system. The threshold levels of the 3 possible

signals can be individually adjusted by means of resistors

R 13/14...R 33/34 (see: T series data sheet) and be used for:

• Save data

• Disconnecting the load or part of it

• Performing a battery test

In systems with battery back-up it may be desirable to extend

system operation in case of long term mains failures by

disconnecting an uncritical part of the load at a certain bus

voltage level, triggered by one of the 3 possible power down

signals. The 2 remaining signals can be set to the low battery

discharge level to get a redundant signal (wired AND) for

finally disconnecting the critical part of the load.

Note: The Power Down signal has an enlarged hysteresis of

approximately 6 V for T 1740 units and 3.5 V for T 1240 units.

The Power Down signal(s) can be combined with the System

Good signal to give a wired AND (see T series data sheet). In

such cases the resulting alarm only becomes active as a

result of a mains failure or a converter failure together with a

heavily discharged battery.

Dimensioning Example of a Battery Charger System

in Single Phase Connection

Battery charger system in single phase connection:

230 V, 50 Hz, load: 1 kW, battery back-up: 3 h

Battery charger:

3 LT 1740 , n+1 redundant configuration, 1.6 kW

Conditions: