NR BR 1875 PDF

This specification applies to Battery Charging Units, suitable for General Railway Signalling purposes, for the Charging of Lead-Acid or Nickel-Cadmium (NICAD) secondary cells.

The general requirements of the units are given in the body of this specification and special electrical output requirements in the relevant "A" series appendix to this specification.

Units supplied to this specification with a Current Output Rating of less than 10A may be housed during their service life in lineside apparatus cases. Units with a Current Output Rating of 10A and greater are generally housed in Relay Rooms.

The units shall not be fused but shall contain internal current limiting protection circuits.

All units supplied to this specification shall have a minimum service life of 25 years.

Manufacturers shall ensure that the equipment complies with the relevant parts of the Health and Safety at Work, etc Act 1974.

If ordered, the units shall contain a power-off detector as specified in Appendix 1.

Chargers to this specification will normally supply batteries with a fluctuating load. Loads may be inductive (i.e. relay coils), or electrically noisy (i.e. static inverter systems). Regulation and power-off detector circuits shall not be adversely affected by loads of these types.

Units may be stored un-energised under warehouse conditions for an indefinite period. The manufacture shall not use any components which require special procedures (i.e. periodic energisation) during such storage to maintain the unit in compliance with this specification.

The battery charger input and output shall be electrically isolated from each other.

The input and output shall be electrically isolated from the battery charger earth/ground.