Switching of MCCB

Switches in MCCB have two main functions: they are usually used to set the main parameters such as trip current and lag time, and they are used as auxiliary switches to perform functions when MCCB trips. Two very different types of switches are needed here.

When setting tripping current, a PCB is usually used to install double-line direct-dial switch. These switches can be rotated (the most common) or occasionally use standard straight-plug keyed dial switches. These switches are rarely used, so reliability is not very important here. However, ensuring that the current is set correctly is critical for safety, avoiding nuisance trip, and ensuring that no downstream equipment is damaged in the event of a failure.

In order to achieve this, in the rotary switch, the contact is designed to have a forward brake, so that the brake can only be set at the integer point of the dialing code. Generally speaking, these switches need to be set up using tools such as small screwdrivers. Because the switch is very small, it is easier to turn the starter with a tool than with a finger. It also provides a certain degree of tamper-proof protection. Many manufacturers offer various types of starters as semi-customized options, and MCCB manufacturers can choose their own starting methods or require special tools.

Auxiliary switches are usually miniature switches, which provide system notification and control of external devices when tripping. Although its usage may not be high compared with other applications, the need to control various devices may be a challenge for designers. Control of warning lights, relays and external power sources may require 10A to 15A currents, while PLC and circuit control may require lower signal currents. To design this dual function on general purpose devices (to achieve configuration flexibility), customized design rather than standard switches is often required.

One of the main requirements of auxiliary switches is to achieve mechanical compatibility with MCCB so that it can be easily and quickly removed when the end user wants to reconfigure various functions. This usually requires customization of standard microswitches to add a molded case with a quick release latch. In many cases, custom wiring has been added to adapt to specific applications and make installation easier.