Global Segment Manager
Industrial & Consumer
Molded-case circuit breakers (MCCBs) provide protection where miniature circuit breakers (MCBs) are too small or inflexible. They typically offer higher current capability, up to thousands of Amperes, as well as the ability to set the trip current on the front panel.
In common with MCBs, MCCBs offer two primary types of fault protection:
In common with almost any electronic/electromechanical device, MCCBs are becoming “connected” and form an essential part of smart factories, where they can be used to monitor and manage the energy usage and cost of running of large machinery.
Also, in common with most electronic/electromechanical equipment, MCCBs rely on switches to provide vital functions including setting the main parameters (trip current and time delays), and as auxiliary switches to execute functions once the MCCB has been tripped.
Setting rotary DIP switches requires a tool or a special actuator for manual use. Many manufacturers offer a wide variety of actuator types as semi-custom options, allowing manufacturers of MCCBs to choose the method of actuation.
Mechanical compatibility with the MCCB, enabling quick and easy removal of the switch for re-configuration, usually involves adding an overmolded housing with quick-release latches as well as customized wiring to suit the specific application and make installation easier.
Two switch types commonly found in MCCBs are as follows.
RTE series – low-profile rotary DIP switch
This RTE series rotary DIP switch is primarily used for setting the trip current and/or time delay.
Figure 1: The RTE series offers designers various options for PCB mounting
The RTE offers 4, 10 or 16 positions, in BCD, Gray or hexadecimal code versions, or a simple single-pole output. Mechanical options include vertical, horizontal (pin-thru and SMD) and reverse versions.
The standard LCP actuator accepts a straight or crosshead screwdriver, or an optional shaft can be specified for manual operation. The top plate can be specified as silver or black, and an ESD protection plate is also available as an option.
The movable contacts are made from gold-plated copper alloy for reliability, and their shape provides a positive detent to each position, ensuring accurate operation. The RTE switches cover the industrial temperature range of -25°C to +85°C.
TM series – miniature snap-acting switches
The UL-rated TM series forms the basis of many custom snap-in solutions for MCCB auxiliary switches.
Figure 2: Versatile and easily customized – the TM series
The momentary-action switches are 15A rated and offer multiple single-pole configurations. Lower-current versions are available in mechanically identical packages for PLC control applications. Other options include the operating force and pivot position of the actuator as well as actuator type.
The switches operate at temperatures between -55°C and +150°C, making them ideal for use in harsh industrial applications. A range of terminations are available, including two sizes of quick-connect solder terminals and screw terminals – and leads can be terminated as required for any factory-produced custom assembly.
In their bare form, either imperial or metric screws typically mount the switches, although customization by C&K to create a snap-in fitting with correctly sized leads is a very popular option that can be arranged by contacting the factory.