Why is relay used in electrical circuits?
As the name implies, it relays low power to high power with galvanic isolation between control input & output.For e.g. you want to control 230VAC bulb from 5VDC electronic circuit.There is another type of relay, called solid state relay. It has no moving parts, can only be used in the AC circuits but control can be DC.
Why do we use relay on control circuit?
Relays work like a very simple remote control switch, which character helps to develop a basic ON or OFF basic logic, is the very fist step to change a system in automatic.Basically relay is an electromechanical device or switch that is open or close by electrical current when flow through it. In a relay, a magnetic force relays the effect of one circuit (control-circuit) to other circuit (load-circuit).To know details about relays, please visit my page RELAYS TO MAKE SWITCHING AUTOMATIC where I shared details.
Why do we need to use contactor in electrical circuits?
The use of a contactor is based strictly on the application. There are different types of contactors from "General Purpose" to types that are specifically designed for the intended application. The PRIMARY difference between a contactor and relay is the ability of the contactor to "make" and "break" the circuit under high current conditions. The contacts in a contactor are designed to handle the in-rush current of the "make" or energized function and the arcing between the contacts associated with the "break" function (de-energized). As far as application is concerned... you need to be more specific in what you are trying to accomplish. As there are as many different types of relays as there are contactors. Using the wrong type in any application can create a lot of problems that using the correct one could avoid. In some applications contactors are a requirement rather than a solution, which is not necessarily true with a relay. The rule of thumb is "You can almost always replace a relay with a contactor and retain the same function, but only in special cases is the reverse true". As far as current limiting is concerned, when this function is added to a relay then it becomes a "Motor Control". The current limiting is to protect the motor it controls and provide contact closures that control ancillary equipment that maybe associated with the motors operation in a system environment such as a manufacturing or production line.
Why do we use a relay instead of a switch?
Hi!Relays are used to control the switching of any equipment electronically. Such as water level in an overhead tank is monitored by some sensor and the pump is switched on or off automatically. Relay is one great step towards automation.There are many types of relays but all are steps to control equipments automatically. We can control a machine which uses high voltage and potentially dangerous, using relays which are controlled by relays, using low power control circuit. Thus we avoid risk of accidents.By use of gas/ smoke operated relays fire alarms prevent fire hazard in buildings, hotels, malls etc.Buchholz relays protect transformers from insulation failure problems. Over current and Earth fault relays protect transformers and transmission lines. And there are so many in the list like Impedance relay, Under frequency relay, Over load relay etc, used to protect the electrical system.Using relays, manual monitoring is minimized and promptness of action is increased. If we monitor some equipment manually, the time taken to act for a preventive measure will be longer than that of relay systems.I think it will be helpful.
Can we use relay as circuit breaker?
No you can not.I really wonder you asked this question. If you know word relay and circuit breaker, you might not have asked this!!Now here is description why you can not use relay as circuit breaker:Fundamental difference between both is circuit breaker is used to make/break circuit and it is designed to carry thousands of ampere, also it has arc quenching mechanism. While relay is device used to make judgement regarding healthiness of the system and upon finding some abnormal condition it will give command to circuit breaker to open. Is is not designed to carry the amount of current which circuit breaker can.
What is the difference between a relay and a switch?
Switch: A control device to control flow of electrons by opening and closing. For example: if you want the light in the room to turn off, you turn the light off (open the switch) and the light turns off. You want to turn it on, you turn the switch on (close the switch the light turns on. The switches could be single or multiple poles and multiple throws.Relay: Relay is kind of a switch which is controlled electronically. So if you have light which you want to turn on and off through motion sensors, you would have to control the light through a relay. It would be if the motion is sensed the control power (usually but not always lower than the load power) will send a signal to the relay which will close the switch to turn the light on. You’d have to design a circuit with a timer or some other mechanism to keep the light on by a steady signal to relay until no motion is sensed for a while and the control voltage will no longer send signal to relay and the light will turn off.
How do I bypass a fan relay circuit board on an AC air handler?
Thor's right. Jump across the wire on the SPT terminal,. (may be black) to the wire on the NO terminal, (should definitely be black) and blower will run continuously until power is shut down to unit. (NC wire is probably red, maybe blue, and is for the lower blower speeds, used for heat) Hope this helps. 20+ yrs hvac tech Black- high speed, blue and yellow will be mid speeds, red will be low speed, white will be common, capacitor wires will be brown. These are standard colors for residential blower motors. If you're not comfortable jumping the motor wires out, by all means, don't do it. For my own purposes, (Buddy's garage furnace) I saved him from buying a $250 control board by using an auxiliary relay to run the blower, bypassing the one on the board....but again, to err on the side of safety, if you're not handy, or don't understand the concept, then Johnie is right. Best of luck.
What are electromechanical relays operated by?
Electromechanical relays are switches that can be operated by electric current. There are two independent electrical circuits - the load circuit and the control circuit. The control circuit consists of a coil which can be magnetized by passing current through it. This magnetized coil pulls a lever causing mechanical switching in the load circuit. A small current in the control circuit (enough to magnetize the coil) can switch large voltages and currents in the load circuit.