What is the value of MOV?
The current rating of the MOV could be twice that of the SMPS rating, meaning if the SMPS wattage is rated at 24 watts at the secondary, then the primary could be calculated as 24/285 = 0.084 amps, therefore the MOV current could be anywhere above 0.084 x 2 = 0.168 amps or 200mA.
How are varistors rated?
The energy rating is determined by volume, voltage rating by thickness or current flow path length, and current capability by area measured normal to the direction of current flow. Littelfuse Varistors are available with AC operating voltages from 2.5V to 6000V. Higher voltages are limited only by packaging ability.
How do I test a MOV with a multimeter?
Work the lead loose with a long-nose pliers. Turn the multimeter on and set its function knob to read resistance. Touch the meter probe tips to the MOV’s leads and measure its resistance. If it has a resistance much under 100 ohms, it has blown.
How do I choose a .MOV size?
The higher the surge rating requirement, the larger the MOV diameter needs to be. In a square MOV, the surge rating is a little higher. For example, a 10 mm square MOV will be rated at about 3.5 kA, a 14 mm square MOV is rated about 8 kA and so on. The square MOV can handle more current as it has a larger area.
How is MOV energy calculated?
Estimate the MOV’s energy rating in units of joules. This is the electrical energy that the MOV can safely absorb at least once before failing. You can calculate the energy by multiplying peak surge volts by amps, and then by seconds of time. For example, 1,000 volts x .
How do I choose a MOV?
The first step of choosing a MOV is determining the continuous working voltage that will be provided across the varistor, you have to choose the varistor with maximum AC or DC voltage that matches or slightly higher than the applied voltage.
How do I specify varistor?
For example, selecting a MOV or silicon varistor for that matter, for voltage, its maximum continuous rms voltage rating should be just above the highest expected supply voltage, say 130 volts rms for a 120 volt supply, and 260 volts rms for a 230 volt supply.