Bus Plugs

Bus Plugs

Bus plugs serve as critical components in a busway system, providing a connection point to the electrical power within the bus duct. They attach to bus bars in the busway, one for each electrical phase, and facilitate the flow of electrical power. A handle and switching mechanism enable the user to control this flow, turning it on or off as needed.

One of the primary functions is to offer overcurrent protection. This is achieved through either bus plug fuses or circuit breakers with a maximum ampere limit. If the current exceeds this limit, the fuses or circuit breaker will interrupt the electrical flow, thereby protecting the machine or component connected to the bus plug.

Safety Features

Bus plugs come equipped with a safety lock mechanism that prevents the door from opening when the plug is in the “on” position. Additionally, some offer the option to secure the plug with a padlock, further enhancing safety.

Flexibility and Relocation

They can be plugged in at various points along the bus duct, which is particularly useful when a machine needs to be moved. The standard spacing for ports is every two feet on both sides of a plug-in section of the busway.

Sizing Considerations

The size is primarily determined by the amperage it is designed to handle. Fusible bus plugs come in standard sizes that correspond to the size of the fuses used for overcurrent protection. These range from a 30-amp maximum to sizes that can handle up to 1600 amps. Circuit breaker bus plugs are sized based on the circuit breaker frame, and their sizes can range similarly.

Voltage and Amperage

It’s crucial to consider the voltage being fed into the busway. Generally, choices are typically 240-volt maximum and 480/600-volt maximum. Bus plug fuses or circuit breakers need to be rated for the appropriate voltage to ensure proper functioning. The amperage also plays a role in the size of the bus plug, with higher amperages necessitating larger plugs.

Wire Connections

Bus plugs require connections for each phase in the bus duct, commonly labeled as A, B, and C. Some busways also include a neutral, requiring a fourth connection. These are referred to as 3-wire and 4-wire bus plugs, respectively.

Grounding

Grounding is another important consideration. Newer systems usually facilitate a ground connection, and the bus plug will have a tab to physically connect to this grounding. In older systems without dedicated grounding, the housing may serve as the ground, and a ground lug can be attached to the enclosure.

Variations

Tap boxes

Tap boxes are similar to bus plugs but are generally used for more permanent connections. They also provide a point of access to the busway’s electrical power.

Breaker Plugs

Breaker plugs are a type of bus plug that uses a circuit breaker for overcurrent protection. They are often used in applications where the overcurrent protection needs to be easily reset.