In switching circuits, transistor operates in cut-off mode for OFF or current blocking condition and in saturation mode for ON condition. The active region of the transistor is not used for switching applications.
When a small current flows though the base terminal supplied by a driving circuit connected between the base and emitter , it causes the transistor to turn ON the collector-emitter path. And it is turned OFF when the base current is removed and base voltage is reduced to a slight negative value. Even though it utilizes small base current, it is capable of carrying much higher currents through the collector- emitter path. A diode can perform switching operations between its high and low state impedance states.
Semiconductor materials like Silicon and Germanium are used for constructing the diodes. Usually, Power Diodes are constructed using Silicon in order to operate the device at higher currents and higher junction temperatures. These are constructed by joining p and n type semiconductor materials together to form PN junction. It has two terminals namely anode and cathode. When the anode is made positive with respect to cathode and by the application of voltage greater than the threshold level, PN junction is forward biased and starts conducting like ON switch.
When the cathode terminal is made positive with respect to anode, PN junction reverse biased and its blocks the current flow like OFF switch. It is most commonly used switching device is power electronic applications. It has three terminals namely drain output , source common and gate input. It is a voltage controlled device i. It is a three terminal semiconductor high speed switching device. These terminals are emitter, collector and gate. A Silicon Controlled Rectifier SCR is one of the most widely used high speed switching device for power control applications.
It is a unidirectional device as a diode, consisting of three terminals, namely anode, cathode and gate. Triac or TRI ode AC switch is a bidirectional switching device, which is an equivalent circuit of two back to back SCRs connection with one gate terminal. Its capability to control AC power in both positive and negative peaks of the voltage waveform often makes these devices to be used in motor speed controllers, light dimmers, pressure control systems, motor drives and other AC control equipment.
A DIAC or DI ode AC Switch is bidirectional switching device and it consists of two terminals, which are not named as anode and cathode as it is a bidirectional device i. This indicates that the DIAC can be used in either direction.
When a voltage is applied across a DIAC, it either operates in forward blocking or reverse blocking mode unless the applied voltage is less than the breakover voltage. Once the voltage is increased more than breakover voltage, avalanche breakover occurs and device starts conducting. A circuit breaker, on the other hand, can be used to protect a circuit that contains many switches or devices. An exception to this is a disconnect switch, which is used to connect or disconnect power to an entire control panel, or machine.
Switches switch and breakers break. These differences are crucial to understanding their safety and practicality. Switches are designed for a high number of operations, how many times the switch is turned on and off.
Circuit breakers are not rated for nearly the same amount of operations. A miniature circuit breaker is a deceiving simple device.
It is a much more complicated device, with more parts, than a switch. Cycling a breaker on and off numerous times will result in its eventual failure.
Circuit breakers can be rated for switching duty for lighting circuits. SWD stands for Switching Duty. HID breakers are rated up to 50A. Circuit breakers may work more effective as safe switches, but they are not switches.
They are not interchangeable. Therefore, using a circuit breaker as a switch is not recommended. A switch cannot detect and interrupt an overload or fault condition. It would more likely melt or burst into flames. Disclaimer: The content provided is intended solely for general information purposes and is provided with the understanding that the authors and publishers are not herein engaged in rendering engineering or other professional advice or services.
The practice of engineering is driven by site-specific circumstances unique to each project. Consequently, any use of this information should be done only in consultation with a qualified and licensed professional who can take into account all relevant factors and desired outcomes. The information was posted with reasonable care and attention. However, it is possible that some information is incomplete, incorrect, or inapplicable to particular circumstances or conditions. We do not accept liability for direct or indirect losses resulting from using, relying or acting upon information in this blog post.
Home White Papers Circuit Breaker vs. Circuit Breaker vs. If the switch is mounted vertically, you would press the top of a rocker actuator or push a toggle actuator upward to move the switch to the momentary OFF position, where all switching circuits would be open. If the switch is mounted vertically, you would press the top of a rocker actuator or push a toggle actuator upward to set the switch to the first ON position.
You would press the bottom of the rocker or move a toggle downward to set the switch to the second ON position. This switch circuit does not have an OFF position, where all switching circuits would be open. This switch circuit does not have an OFF position where all switching circuits would be open.
You would move the rocker or toggle actuator to the center position to set the switch to OFF, where all switching circuits would be opened. When the actuator is released, it will return to the center OFF, at rest position. You would press the bottom of the rocker or move a toggle downward to set the switch to the maintained ON position. From this position, you would manually move the rocker or toggle actuator to the center position to set the switch to OFF, where all switching circuits would be open.
If the switch is mounted vertically, you would press the top of a rocker or push a toggle actuator upward to move the switch to the first momentary ON position. You would press the bottom of the rocker or move a toggle downward to move the switch to the second momentary ON position. This is a normally open N. Most commonly this circuit function is offered in a two-pole configuration where each pole controls a separate circuit.
If the switch is mounted vertically, you would press the top of a rocker or push a toggle actuator upward to move the switch to the Circuit 2 ON position. You would press the bottom of the rocker or move a toggle downward to set the switch to the Circuit 1 ON position. You would move the rocker or toggle actuator to the center position to move the switch to the Circuit 1 ON position. You would press the bottom of the rocker or move a toggle downward to set the switch to the OFF position.
When the actuator is released, it will return to the center Circuit 1 maintained ON position.
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