Different Types of Electrical Switches and Their Use

Different Types of Electrical Switches Normally Used in Circuits

There are so many types of electrical switches available from very simple to very complex switches used in the electrical circuit controlling systems. 

The switch may be different types but the basic function of the electrical switch is to open or close. The meaning of an electrical switch is to open or close the electrical path to equipment. 

What are the different types of electric switches that are used in every home?

When we name the switches, we find some common and lovely switches as below:

 SPST- Single pole, single throw switch. It is a simple on-off switch just having two terminals that are either connected together or disconnected from each other by phase P1 and terminal T1.

It is also classified into two types: SPST-NO-single pole, single throw, normally open known as Type-A, and SPST-NC- single pole, single throw, normally closed known as Type-B. 

The most common and simple type of electric light switch is the one-way switch. A very simple one-way press operation and instant effects. Their operational simplicity makes user comfort a reality.

 

SPDT-  Single pole, double throw. It is a simple break-before-make changeover switch. The common terminal is connected either to Terminal T1 or Terminal T2.
Similar to SPDT some manufacturers use SPCO/SPTT meaning single-pole changeover or single-pole, centre off, or single-pole Triple Throw for switches. 

Two-way switches are very different and are extensively found in modern homes that have a limited number of switching accessories. Their usage is very efficient and adds to the convenience of the users significantly.

DPST- Double pole, single throw. DPST is actually equivalent to two SPST switches together controlled by a single mechanism.

DPDT- Double pole, double throw. DPDT is actually equivalent to two SPDT switches controlled by a single mechanism. 

Some manufacturers use DPCO - double pole changeover for switches with a stable center position. 

2p6t- Two-pole, six throws. 2p6t is actually a changeover switch with a common terminal that can connect to L1 to L6 with a two-pole second switch controlled by a single mechanism.

What type of switch is used in an electrical panel?

The switches used in electrical panels may be manual switches or automatic switches. The manually operated switches such as light switches, fan switches, or manual switches for any kind of electrical circuit of electrical equipment.

Automatically operated different switches can be used to control the motions of machines such as to indicate a door has reached its full open position or full close position.

Switches may be operated by process variables such as pressure, temperature, flow, current, voltage, and force, acting as sensors in a process and used to automatically control a system. There are many different switch designs. The most common electrical panel switches are:

Slide switch: A slide switch has a knob that you can slide back and forth to open or close the contacts. Slide switches we find as SPST (single pole single throw), and DPDT (double pole double throw) switches.

Toggle switch: A toggle switch has a lever that we flip up or down to open or close the contacts. The common light switch used in household wiring is an example of a toggle switch. Toggle switches are actuated by a lever angled in one of two or more positions. The most famous type of toggle Electrical Switches contains two positions.

Rotary switch: A rotary switch has a knob that we turn to open and close the contacts. The switch in the base of many tabletop lamps is an example of a rotary switch.

Rocker switch: A rocker switch has a seesaw action. We press one side of the switch down to close the contacts and press the other side down to open the contacts.

You may read the circuit-switch 

MCB: MINIATURE CIRCUIT BREAKER OPERATION BASIC

 

Knife switch: A knife switch is the kind of switch Igor throws in a Frankenstein movie to reanimate the creature. In a knife switch, the contacts are exposed for everyone to see.

Mercury switch: The mercury switch consists of a drop of mercury inside a glass bulb with 2 contacts. The two contacts pass through the glass and are connected by the mercury when the bulb is tilted to make the mercury roll onto them.

Push-button switch: A push-button is simply a button-switch mechanism for controlling some aspect of a machine or a process.  Even many un-biased buttons require a spring to return to their un-pushed state. These switches are used for bell circuits, and refrigerator lighting circuits. Some push-buttons in the industry also contain indication lights such as Red, Green, and yellow.

Special types of switches are:

Differential Pressure switch: A differential pressure switch is a device that utilizes a differential air pressure to actuate an electric switch at a preset actuation point. This may be the difference between two positive or two negative pressures, one of each, or positive and atmospheric or negative and atmospheric pressure. The electric switch may be used to start or stop motors or fans, open or close dampers or louvers, light a warning signal, sound alarms, etc.

Foot-switch: Some machinery like garment factory sewing machines use a footswitch that is operated by foot instead of hand.

Reversing switch: Reversing switch is an electric switch that has four terminals capable of being connected in pairs in two different ways so as to reverse the direction of the motor.

You may read the different types of switches in detail in another article:

1. How to Select Control Switches, Selector Switches, and Auxiliary Switches;
2. Automatic Transfer Switch Diagram And Operation Procedure;
3. How Do Electronic Thermostats Work In HVAC Systems?;

28 Basic Symbols of Electrical Switches that Use Widely

The symbol for electrical switches is important to electricians to select proper switches during wiring.

The following 28 switch-symbol is the most commonly used stitches in our workplace.

This is not the limit, there are many switches and switch-symbol for them.

You may read another article to know the detailed wiring system on-

ELECTRICAL DISTRIBUTION BOARD DB WIRING.

Top Brands Electrical Switches That are Used in Bangladesh

Siemens - Huge scale of operation and range, adapted to Bangladesh, electrical switches of Siemens work irrespective of the load, and products are reliable. In a house, Siemens switches and sockets are used as the first choice in high-grade equipment.

Schneider - a French multinational, develops technology and solutions that make energy safe, reliable, efficient, green, and productive. Schneider switches and sockets are popular in the industry sector.

Legrand -Widely used in Bangladesh as switches and sockets of miniature circuit breakers and distribution boards.

Havells - an Indian company, the switches and sockets are widely used in India and Bangladesh.

Wipro - Modular switches are equipped with glossy finish switches that flaunt radium markers for visibility at night, a protective spark shield for added safety, thermostat housing for safe electrical insulation, and silver-coated metal parts for better current conductivity.

Polycab - specializes in high and low-voltage switchgear and a different range of solutions that are suitable for all kinds of HV/LV power engineering requirements including protection, metering, and control equipment.

Orpat - Gujarat-based company, known for silver series modular switches and copper series modular switches, which are gradually gaining in popularity in the country.

What is the Difference between Isolation and Switching?

The consumer’s main switchgear must be readily accessible to the consumer and be able to:

1. isolate the complete installation from the supply;
2. protect against overcurrent;
3. cut off the current in the event of a serious fault. The regulations identify four separate types of switching: switching for isolation, switching for mechanical maintenance, emergency switching, and functional switching.

Isolation

 is defined as cutting off the electrical supply to a circuit or item of equipment in order to ensure the safety of those working on the equipment by making dead those parts that are living in normal service.

The purpose of isolation switching is to enable electrical work to be carried out safely on an isolated circuit or piece of equipment. Isolation is intended for use by electrically skilled or supervised persons. 

An isolator is a mechanical device that is operated manually and used to open or close a circuit offload. An isolator switch must be provided close to the supply point so that all equipment can be made safe for maintenance. 

Isolators for motor circuits must isolate the motor and the control equipment, and isolators for discharge lighting luminaires must be an integral part of the luminaire so that it is isolated when the cover is removed or be provided with effective localization (IET Regulation 537.2.1.6). 

Devices that are suitable for isolation are isolation switches, fuse links, circuit breakers, plugs, and socket outlets. They must isolate all live supply conductors and provision must be made to secure the isolation (IET Regulation 537.2.2.4).

Isolation at the consumer’s service position can be achieved by a double-pole switch that opens or closes all conductors simultaneously. On three-phase supplies, the switch need only break the live conductors with a solid link in the neutral, provided that the neutral link cannot be removed before opening the switch.

The switching for mechanical maintenance

requirements are similar to those for isolation except that the control switch must be capable of switching the full load current of the circuit or piece of equipment.

The purpose of switching for mechanical maintenance is to enable non-electrical work to be carried out safely on the switched circuit or equipment.

Mechanical maintenance switching is intended for use by skilled but non-electrical persons. Switches for mechanical maintenance must be manually operated, not have exposed live parts when the appliance is opened, must be connected to the main electrical circuit, and have a reliable on/off indication or visible contact gap (IET Regulation 537.3.2.2). 

Devices suitable for switching off for mechanical maintenance are switches, circuit-breakers, and plug-and-socket outlets.

Emergency switching

 involves the rapid disconnection of the electrical supply by a single action to remove or prevent danger. The purpose of emergency switching is to cut off electrical energy rapidly to remove an unexpected hazard. Emergency switching is for use by anyone. 

The device used for emergency switching must be immediately accessible identifiable and capable of cutting off the full load current.

Electrical machines must be provided with a means of emergency switching, and a person operating an electrically driven machine must have access to an emergency switch so that the machine can be stopped in an emergency. 

The remote stop/start arrangement could meet this requirement for an electrically driven machine (IET Regulation 537.4.2.2). Devices that are suitable for emergency switching are switches, circuit breakers, and contactors. 

Where contractors are operated by remote control they should open when the coil is side-energized, that is, fail-safe. Push buttons used for emergency switching must be colored red and latch in the stop or off position. 

They should be installed where danger may arise and be clearly identified as emergency switches. Plugs and socket outlets cannot be considered appropriate for emergency disconnection of supplies.

Functional switching

Involves the switching on or off, or varying the supply, of electrically operated equipment in normal service. The purpose of functional switching is to provide control of electrical circuits and equipment in normal service. Functional switching is for the user of the electrical installation or equipment.

The device must be capable of interrupting the total steady current of the circuit or appliance. When the device controls a discharge lighting circuit it must have a current rating capable of switching an inductive load. 

The regulations acknowledge the growth in the number of electronic dimmer switches being used for the control and functional switching of lighting circuits. The functional switch must be capable of performing the most demanding duty it may be called upon to perform (IET Regulations 537.5.2.1 and 2).