DC uninterruptible power supplies are used for:
• Closing and tripping of circuit breakers and contactors in switchboards.
• Switchboard indicating lamps.
• Radio communication equipment.
• Emergency generator control panels.
• Start-up and shut-down lubricating oil pumps and auxiliary systems for gas turbines, large pumps and compressors.
When specifying the battery and charger system the following points should be considered.
• Rated voltage and current.
• Rated ampere-hour capacity.
• Rate of discharge
• Type of cell i.e. lead-acid or nickel-cadmium
• Ventilated batteries. Some types of cells can be non-venting but this greatly influences the charging process.
• Type of charger e.g. rectifier or thyristor.
• Boost, float and trickle charging requirements.
• Duty and standby units, and their interlocking and control philosophy.
• Volt-drop considerations in the DC outgoing cables.
• Overload and short-circuit protection.
• Tolerance on the DC output voltage during all load and charging conditions.
• Ambient temperature and appropriate derating factors for the cells and the charger.
