July 16, 2021

What is SwitchGear and Components used in Switchgear?

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The devices used for switching, protecting, and controlling in any electrical circuit are known as Switchgear. Switchgear comprises High voltage switchgear, medium voltage switchgear, and low voltage switchgear. Today we will see Low voltage switchgear. 

Let us see which electrical components are used in Low voltage Switchgear. 

The main parts of Switchgear are ACB, MCCB, Contactor, Relay, SPP, Capacitor, Starter, Isolator, Switch fuse unit, MCB, ELCB, MPCB, HRC, and HBC fuse and fuse base and Changeover Switch. An air circuit breaker is the primary protection device of any switchgear. 

For any high-power-consuming device like Panelboard, power is distributed through ACB. This device cuts the primary circuit during Earthfault, overcurrent, Undervoltage and short-circuits, due to which the circuits connected through it are prevented from getting fail/damage. 

An air circuit breaker is of 3-pole or 4-pole. It ranges from 630amp to 10,000amp Moulded case circuit breaker is used to protect high load current devices. MCCB protects high-load current devices from fault and overloading. The tripping mechanism in MCCB is Thermal based, Microprocessor based or Electronic based MCCB is of 3-pole or 4-pole. 

A contactor is the most demanding component of Switchgear. This is an electrically operated switch. Inside the contractor, there is an electromechanical system connected to the coil. It works on the predefined supply being provided to the ring. 

The relay may be a switching device electromechanically and electronically controlled to open or close the relay. Relay are of different types such as Thermal relay, CT operated relay, solid-state relay, hybrid relay, electromechanical relay and electronic relay Single phasing preventer(SPP). 

Motor wiring or circuit may get damaged due to failure of any phase in 3 phase motor. Sep detects a fault in 3 steps and blocks current in case of failure in any stage, thus prevents the engine from getting damaged. To maintain the power factor, the capacitor is used. 

The capacitor is usually air-cooled or water-cooled, which is of Dry-type, MPP (metalized polypropylene) type, and APP (all polypropylene) type. Star delta starter comprises three contactors, one relay, and one-timer. 

In any circuit, if the present increases from a predefined limit, the relay in starter gets trip, blocking the current flow through the contactor, thus preventing the motor from damaging. To operate a circuit manually (ON/OFF), an Isolator is employed. The Isolator doesn’t contain any protection or tripping device. 

Its OS is manually independent, quick make and quick break. The switch fuse unit may be a complete unit for controlling the MCC panel and PCC panel. It is used for power distribution and protection of electrical devices. 

It is generally of 3-pole,3-pole+neutral and 4-pole. MCB, Miniature circuit breaker. It is a mechanical device that protects the low circuit from overcurrent. Mcb has a tripping mechanism that may reset easily. Mcb is of 1-pole, 2-pole,3-pole and 4-pole. Earth leakage circuit breaker is a safety device that protects the circuit from fault and earthing and humans from electric shock. 

It detects fault within the course and gets tripped, thanks to which the flow of current gets blocked; hence circuit gets prevented from getting damaged. MPCB, motor protection circuit breaker. It protects the motor from short circuit current and overloads current HRC fuse means a High rupturing capacity fuse. 

In any circuit, the fuse may be a guard. Inside the porcelain body, a fuse wire or element allows flowing short circuit current or heavy overcorrect. If fault or overcurrent becomes normal in a given time, then fuse remain because it is or gets melt in other case and therefore the circuit connected to it gets disconnected. 

The fuse is housed inside the fuse base. Changeover switch. Through it, any electrical load are often employed by two power source, one by one. In this, if one supply fails, 

can use the other one is the entire system of this switch.

Advantages And Disadvantages Of Low-Voltage Switchgear


The advantages are:

  • Easy installation and maintenance.
  • Good protection performance.
  • High breaking capacity.
  • Large capacity.
  • Solid dynamic stability.
  • Comprehensive electrical solutions.
  • High segmentation capability
  • Good dynamic thermal stability
  • Advanced and reasonable structure
  • Various scheme units combined arbitrarily
  • Can accommodate more circuits
  • Floor space-saving
  • High protection level
  • Safe and reliability
  • Convenient maintenance.


There are very few loops, so the units can’t be combined arbitrarily, take up a lot of space, and cannot communicate with each other. The cabinet’s top contains the horizontal bus, while the vertical bus does not have a flame-retardant plastic board. They can’t communicate with the computer.


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