What kind the types of switches, There are many different types of switches: Push-button Switch, Toggle Switch, Rotary Switch, Multipurpose Rotary Swi
There are many different types of switches. Switches have one thing in common. They all do only one thing. They open or close an electrical circuit. Recall that an open circuit has a break in it and current can not flow through it. A closed circuit is complete so current can flow through it. No matter how they work or how they are tripped (activated), the end result is the same. An electrical circuit is either opened or closed by a switch.
Switches are control devices used to operate electrical equipment. Switches open and close the electrical circuits which give power to the equipment. There are many different kinds of switches. There are switches that are activated by changes in process variables. For example, a rise or fall in temperature or pressure. There are switches that are tripped by electronic circuits. Switches can be simple or complex.
1. Push-button Switch
A very simple kind of switch is the push button. There are two types of push button switches:
NO = Normally Open (push it to close)
NC = Normally Closed (push it to open)
All push-button switches work in the same way. A spring in the switch holds the button open or closed. A fail open switch will cut off all electrical current in a circuit if there is a fault or failure in the system. Most emergency shutdown systems use the FAIL OPEN system. Switches in the system are normally closed. They will open if there is a fault.
2. Toggle Switch
Some toggle switches do not have a spring like the push-button switches. The toggle switch will stay in the position it is set, open or closed. Other toggle switches have springs in ' them. Their normal position is neutral, neither on nor off. The switch is moved to one position or the other, but when it is released, the spring returns it to the neutral position.
The word Rotary in rotary switch simply means that you turn the switch in a circular direction (rotate it) to operate it. Figure shows a simple ON/OFF, two position, rotary switch.
4. Multipurpose Rotary Switch
Multipurpose means that the switch serves more than one purpose. Figure is actually a circuit breaker switch. A circuit breaker is a device that protects electrical equipment from too much current. When the switch is off, the circuit is off. The type of switch is often used on electrical control panels.
Turning the switch directly to the ON position will not activate the circuit.
The switch must first be turned to the RESET position, then to ON. In the ON position the switch closes a circuit breaker. Turning the switch to the OFF position opens the circuit breaker and deactivates the circuit. We will look at circuit breakers later in the unit.
5. Spring Loaded Rotary Switch
Figure shows an example of a spring loaded switch. The switch is normally in the position shown. It is in a neutral position, which means it is not doing anything. The operator can turn the switch to the position he wants. If the circuit is off (broken) he turns the switch to START. When he releases the switch, a spring in the switch returns it to the neutral position. To break the circuit, the operator turns the switch to STOP. When he releases the switch, the spring in the switch returns it to the neutral position again.
6. Rotary Selector Switch
Figure is a rotary selector switch found on a gas turbine engine control panel. The switch is a complex rotary switch. This type of switch allows an operator to select the function he wants to perform. We have said earlier that a switch does one thing. It opens or closes a circuit. The switch in figure is still only opening or closing a circuit. The switch selects which circuit to open or close.
