The DC power distribution box is an intermediate device between the rectifier, the battery and the DC load in the DC power supply system, and has the functions of circuit conversion, protection, control, measurement and sending out alarm signals.
1. The device should have access to two sets of batteries that are charged when the gadget is in use. The DC power distribution box should have a safeguard feature for the batteries when the DC current rating is larger than 400A, according to the requirements of use. The batteries are automatically disconnected when the battery voltage falls below the discharge termination voltage, and they are automatically or manually connected once the equipment's output voltage rises.
2. A secondary download option should be available on DC distribution panels for mobile communications. Before the battery is discharged to the average termination voltage after the AC power supply is interrupted, a portion of the secondary load is removed first, allowing the battery to supply the important load for an extended period of time, this is a process known as secondary download or secondary down power.
3. At rated load, the discharge circuit voltage in the DC power distribution box shall not excelled 0.5V.
4. Surge absorption devices should be installed at the output end of the DC power distribution box, as well as over-voltage and over-current protection devices.
5. The maximum monitoring error for the DC power distribution box output voltage is 0.5V.
6. A functioning grounding system and a safe grounding device should be installed in the DC power distribution box. Working grounding in a DC power distribution box is normally done with the positive pole; if the negative pole is utilized, special procedure must be followed. The metal shell of the distribution equipment and the DC power distribution box's protective grounding device between the grounding screws, there should be a secure electrical connection with a contact resistance of less than 0.1Ω.
7. The DC power distribution box must be able to work in parallel with similar-type equipment.
8. Telemetry and telecommunication. The following are examples of what a DC power distribution box can communicate and telemetry.
1) Telecommunications: DC output voltage is too high or excessively low, resulting in a fuse failure; the battery voltage is low, resulting in broken disconnect switch.
2) Telemetry: DC output voltage, total DC output current, charging and discharging current of the battery pack. The current of the main branch circuits can be telemetryed by the DC power distribution box as needed.
9. The DC power distribution box's output taps. The quantity and capacity of output taps should be set to satisfy the telecommunication equipment's requirements. The sum of the loads used simultaneously on the output taps must not exceed the distribution equipment's rated capacity. Protection devices are required for output taps with a capacity more than 630A, however protection device are not required for DC output taps with a capacity greater than 630A.