Three Requirements and Three Functions of AC Power Distribution Boxes

Structural Requirements of AC Power Distribution Box System

Heat Dissipation

In high-altitude areas, due to low air pressure and low air density, heat dissipation conditions are relatively poor, significantly affecting the performance of low-voltage electrical equipment. Therefore, when designing capacity, allowance must be made to reduce the temperature rise during equipment operation. Special environmental conditions, like those in Tibet, should be fully considered during the design. AC power distribution boxes should be equipped with stable low-voltage electrical components and have sufficient allowance to ensure reliable system operation.

Maintenance and Repair

The AC power distribution box should adopt an external opening double-sided maintenance structure, made of welded thin steel plates and angle steel. Operation can be performed through a door that can be opened at the front of the panel; the upper part of the panel is equipped with an instrument panel that can accommodate various indicator instruments. The overall design should facilitate maintenance and repair to reduce downtime and improve operational efficiency.

Grounding

The AC power distribution box needs to have a good grounding protection system. The main grounding point is usually welded to the framework at the bottom of the cabinet, and the grounding point of the instrument panel should be connected to the cabinet, forming a complete grounding protection circuit. This design effectively prevents operators from electric shock, ensuring safety.

Protection Functions of the AC Power Distribution Box

The AC power distribution box should have protection functions against various circuit faults during operation. Once a protection action occurs, users can follow the prompts to troubleshoot the fault and restore power supply.

Output Overload and Short Circuit Protection

When a short circuit or overload fault occurs in the output circuit, the corresponding circuit breaker will automatically trip and cut off the power supply. In severe cases, it may cause the fuse to blow. At this point, the cause of the fault needs to be identified and corrected before the load can be reconnected.

Input Undervoltage Protection

When the system input voltage drops to 70%-35% of the rated voltage, the input control switch will automatically trip and cut off the power; when the input voltage is lower than 35% of the rated voltage, the circuit breaker will be unable to close and supply power. Under these circumstances, the power supply voltage needs to be checked and adjusted until it returns to normal before power can be restored.

In addition, when the AC power distribution box is powered by inverter input, the system also has a battery undervoltage protection function. When the battery discharge depth reaches a certain value, the controller will signal to cut off the load to prevent battery over-discharge damage.

Input Interlock Protection

In photovoltaic power stations, the AC power distribution box has the most crucial safety protection feature—input interlock protection. This function is achieved through the dual protection of relays and circuit breakers. When either the inverter or diesel generator input is energized, the relay of the other input cannot close, thus avoiding multiple inputs being connected simultaneously.

This design ensures that only one switch can be closed to supply power. If an attempt is made to close both switches simultaneously, both power sources will automatically trip and cut off the power.

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