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There are basically two parts to a relay. The control voltage side when energized passes a current through a coil that activates a solenoid and opens or closes a switch. This is typically a small current. The current in the switch should be rated on the device and is usually quite a bit higher than the control current.
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What size resistor is needed to allow a 220 volt coil in a relay operate on 277 volts?
You will need to know the amount of current flowing through the coil when 220 volts is applied across it. A resistor in series with the coil will limit the current so that the coil only sees 220 volts. The resistor will need to drop 57 volts. So, 57 volts divided by the current in amps will give you your required resistance. You will need a resistor with a high power dissipation rating with 57 volts across it. Your resistor will probaly need to dissipate several watts. For example: A 220 volt coil with 300 milliamps (.3 amps) will require a resistor of 733 ohms. The power dissipation of the resistor would need to be 17.1 Watts! You might try using a light bulb as a series resistor. Ensure that it can handle 57 volts. To complicate matters, is that AC or DC you are using? AC relays have inductance build in, in order to increase the specific "ac resistance", thus the same coil could use as little as 0,001A so you will need a very low value resistor. Anyway, if any 220V relay uses as much as 300mA, I doubt if you will be able to pick it up with one hand! Such a relay coil will draw about 66W of power! I have a 16A rated contact 230V relay. Its current is 0,0015A that is equivelant to 0.33W at 220V!
Why a coil of wire placaed in series circuit allows low frequency current but not high frequency current to pass?
The opposition to an alternating current offered by a coil, or inductor, is called impedance (symbol Z, measured in ohms) which, in turn, is made up of two components: resistance (symbol R) and inductive reactance (symbol XL). These three quantities are related as follows: Z2 = R2 + XL2.The resistance of an inductor is a fixed value which depends upon the length of the coil's wire, the cross-sectional area of the wire, and the resistivity of the material from which the wire is made.The inductive reactance of an inductor, on the other hand is directly proportional to the frequency of the supply. So, at high frequencies, an inductor's inductive reactance is very much higher than at low frequencies.So, at high frequencies, the impedance of the inductor is higher because its inductive reactance is higher.The current flowing through a coil is, by Ohm's Law: I = V / Z. So, at high frequencies, the inductor's impedance will be much higher than at low frequencies, which means that a very much smaller current will flow when the frequency is high compare to when the frequency is low.
What is Magnitude of the voltage or current?
"Magnitude" means how strong it is - how much voltage (how many volts), or how much current (how many amperes).
How can a relay circuit be used?
A relay circuit is typically a smaller switch or device which drives (opens/closes) an electric switch that is capable of much larger current amounts or a circuit which operates the coil or electronic actuator from one source and uses a separate power source to drive an isolated device. For the use in electrical engineereing:Generally speaking, using a relay may involve anything from a very robust approach to an extremely delicate approach. Consider some aspects of a relay. A relay has contacts, arcing and sparking because of back e.m.f from load circuits may damage these contacts and reduce the life span of the device. Some inductive applications might require a low value capacitor across the relay contacts. Just remember that the peak voltage (not rms or AC) of the mains running through the contacts is not more than the rated capacitor voltage value. Do not use polarized capacitors where AC is used. Often a 10nF might make a difference already depending on your back e.m.f of the load obviously. It will also reduce some EMI (electromagnetic interference)Even if your DC control signal may only see resistance of the coil at the time the coil is on or off. A coil that has inductance and store magnetic energy, the same as any coil will also produce back e.m.f when potential is removed. The collapse of the magnetic field cause a high potential difference, possibly thousands of volts at high frequency. The frequency may in fact be so high that regular diodes or transistors might not stop it. One would recommend a series resistor and use the collector of a NPN transistor with it's emitter to the ground to switch the relay on or off via the base, be sure to have a base resistor to protect the source of the control signal as well as the B-E junction of the transistor, calculation as follow:Rs = collector series resistorRb = is base series resisterbeta = current gain for the transistorVsource = the control signal voltage minimum that will turn relay on or offBy applying ohm's law we get:Rc = [Rrelay x (VCC-Vrelay -Vce)]/(Vrelay )Rb = (Vsource-Vbe)/[(Vrelay/(Relay x Beta)) x 10]{use factor 10 to compensate for error in beta values}Don't ever be to comfortable with the fact that there are no electrical connection between the contacts and the coil of a relay. Do not think relays are safe to use with computers or related micro controller devices because they are electrically isolated. It will be a bad mistake!! There are back e.m.f. from the coil aswell as e.m.i from contacts what is induced back into the coil when it has high impedance across it.It's then recommended to have a fast recovery diode in reverse bias condition across the coil to prevent back e.m.f. of finding its way back home.This is recommended to protect the driving signal source. Often in small relays using HC or TTL family logic to drive it via a transistor to a transorb or fast recovery diode across the coil may be good enough. Especially if you use it for your self and not to design a heart-lung machine for a hospital.But if you have micro controllers, computer ports. The damage of a strong back e.m.f may be more than what you bargain for and will probably happen at the worst time in the wrong place. The best is to use a opto-coupler.The control source will via a series resistor, let say about (330R for a 5V signal) switch an internal LED inside the opto-coupler device on. The light will drive a photo-transistor into forward bias condition. That can be used to drive the transistor that will energize the relay. Since there is no electrical connection between the output pin of the microcontroller that produce the control signal and the relay coil. There is only a one way communication via a light beam. This is by far safer. It creates a typical, 2500V isolation between the robust electrical circuit and it's e.m.f 's, and the sensitive and delicate micro controller or computer circuit environment. A dip in Vcc or pin for less than a millionth of a second dipping with 2 volt or spiking can cause freezing, erratic response or failure of the micro controller. For good electronic design opto-couplers are a very important part of a reliable control system that use micro controllers to control relay output with.
Electromagnets are created using what?
An electric current flowing in a wire creates a magnetic field around the wire. To concentrate the magnetic field of a wire, in an electromagnet the wire is wound into a coil, with many turns of wire lying side by side. The magnetic field of all the turns of wire passes through the center of the coil, creating a strong magnetic field there. A coil forming the shape of a straight tube (a helix) is called a solenoid; a solenoid that is bent into a donut shape so that the ends meet is called a toroid. Much stronger magnetic fields can be produced if a "core" of ferromagnetic material, such as soft iron, is placed inside the coil. The ferromagnetic core magnifies the magnetic field to thousands of times the strength of the field of the coil alone. This is called a iron-core electromagnet.
What is the difference between an earth fault relay and an over current relay?
earth fault relay is also a type of over current relay but the set value of current or relay sensing current is much less than the maximum load current.in over current relay relay sensing current ise than maximum load current mor
Can you show the connection diagram of REF relay?
the ref relay rct secondary output how much current
How does a contact relay weld?
Too much current cause excessive heat and cuases melting of the relay contacts.
How much current flows in welding cable?
It means scondry and primary coil how current flow in weldingp plant.
What is Overload Solid State relay?
a relay that detects the amperage the motor is drawing when the motor dwaws too much to drops out the coil voltage to shut down motor and prevent damage
Will a relay with a 40 amp rating function properly in a circuit with a 30 amp fuse?
Yes. The rating of a relay is how much current it can switch on and off, not how much it uses or must have.
1994 ford ranger 3.0 cranking but not firing good module coil fuel pump relay eec relay fuel pump is pumping but not sure how much Any ideas?
eec relay fuse under hoodType your answer here...
What is the uses of relay?
The RELAY CIRCUIT used in electronics circuits for ,1. It is used for general mechanical SWITCH.2. It is used in High voltage switching mechanisms3. It is used in High voltage and current Applications.
What size resistor is needed to allow a 220 volt coil in a relay operate on 277 volts?
You will need to know the amount of current flowing through the coil when 220 volts is applied across it. A resistor in series with the coil will limit the current so that the coil only sees 220 volts. The resistor will need to drop 57 volts. So, 57 volts divided by the current in amps will give you your required resistance. You will need a resistor with a high power dissipation rating with 57 volts across it. Your resistor will probaly need to dissipate several watts. For example: A 220 volt coil with 300 milliamps (.3 amps) will require a resistor of 733 ohms. The power dissipation of the resistor would need to be 17.1 Watts! You might try using a light bulb as a series resistor. Ensure that it can handle 57 volts. To complicate matters, is that AC or DC you are using? AC relays have inductance build in, in order to increase the specific "ac resistance", thus the same coil could use as little as 0,001A so you will need a very low value resistor. Anyway, if any 220V relay uses as much as 300mA, I doubt if you will be able to pick it up with one hand! Such a relay coil will draw about 66W of power! I have a 16A rated contact 230V relay. Its current is 0,0015A that is equivelant to 0.33W at 220V!
Does CD have a magnet on it?
Most CD players use electromagnetic switches called relays. Have you ever turned on the power on your CD player or another appliance, and heard a click immediately before it went on? That's a relay doing its job. In a relay, a small current runs through a coil which is right next to a switch with a magnet in it. The coil pulls on the switch, closing it and turning on the device. Relays are useful because they use a small current to control a much larger one. As a result, they are often used in the power supplies of electronic devices such as CD Players
How much weight can the knee joint withstand?
As such any joint can not withstand much weight. It is the support of strong muscles, which make the joint to withstand much higher weight.
Will the relay switch effect the cooling fans?
Yes. Most cooling fans are controlled by a relay because they take too much current to be wired directly.
