Contents
How do you calculate varistor?
Touch one meter probe to the free varistor lead and the other probe to the connected lead. Read the resistance on the meter. If it reads nearly infinite resistance, the varistor is still good. If it reads very low resistance, the varistor is blown.
What is varistor protection?
Varistors are used to protect a circuit from high voltage surges. When a high voltage surge is applied to a circuit, the outcome is usually catastrophic to the circuit. When a voltage surge exceeding a specified voltage (varistor voltage) is applied, the varistor suppresses the voltage to protect the circuit.
What is MOV in SMPS?
Abstract: Metal oxide varistors (MOV) are popularly used to protect offline electronic equipment against power line transients. The offline switched mode power supplies (SMPS) use power line filters and MOVs in the front-end.
What is the symbol for LDR?
The LDR symbol used in electronic circuits is based around the resistor circuit symbol, but shows the light, in the form of arrows shining on it. In this way it follows the same convention used for photodiode and phototransistor circuit symbols where arrows are used to show the light falling on these components.
What is MOV circuit?
A Metal Oxide Varistor (MOV) is a protection component used in power supply circuits that is powered directly from AC mains. It is used to protect the circuit from high voltage spikes by varying its resistance.
What should the maximum AC voltage be for a varistor?
Maximum AC Voltage: It is the maximum RMS line voltage that can be given to the varistor constantly, the maximum RMS value should be chosen to be slightly above the actual RMS line voltage. The peak voltage of the sine wave should not overlap with the minimum varistor, if it does, it might reduce the lifetime of the components.
How is the dissipation of an AC varistor calculated?
Case 2—Calculating ac Dissipation: When a sinusoidal alternating voltage is applied to a varistor, the dissipation is calculated by integrating the VI product. A suitable expression is as follows: Transient energy ratings are quoted in Joules.
How to choose the best varistor for your circuit?
You should choose the varistor that can dissipate more energy that is equivalent or slightly greater than the energy dissipation required during the surge that the circuit can produce. Calculate the peak transient current or the surge current through the varistor.
How to calculate peak transient current in varistor?
Calculate the peak transient current or the surge current through the varistor. You should select the varistor that has the surge current rating equal or slightly greater than the current rating required by an event that the circuit may produce to make sure it functions properly.