Introduction of current measurement by switch
Release time：2018-11-10 Clicks： Click
How large is the current through the switch, how can it be measured, and what is the specific measurement method? The following is a detailed introduction to you.
The advantages of this measuring method are quite intuitive and convenient. The disadvantage is that the current passing through the switch is very small and the oxide film on the contact surface can not be destroyed, which results in a large recognition error (on the large side). Therefore, this method is not recommended in the circuit resistance measurement of high voltage switches.
Indirect measurement by voltage drop method (volt-ampere method): Voltage drop method is the value of DC current through the switch socket. Voltmeter is used to measure the voltage drop (mV) between the inlet and outlet lines of the switch socket. Then the main circuit resistance of the switch socket is calculated by Ohm's law.
A measuring circuit with a transformer and a silicon rectifier. At the same time, the voltage drop method is recommended to measure the main circuit resistance of switching socket because the current passing through the test is large enough to destroy the metal oxide film on the contact surface, reduce the measurement error, and the measured value is more accurate. Therefore, the voltage drop method is recommended to measure the main circuit of switching socket.
The tedious calculation of the switching switch shows that if the attenuation time constant of the switch socket circuit is set at 45ms, the phase A and B circuits are connected simultaneously, and the DC component in phase A and B reaches o.866, the maximum DC component in phase B (assuming it happens to be a side phase) can reach 112%.
If the decay time constant in the switching socket system is increased to 60 ms, the maximum DC component in the six-phase (three-phase) system will reach l15%. In the "split" test, the DC component at the instant of contact separation is related to the duration of short circuit, that is, the opening time of circuit breaker and the action time of relay protection.