Leakage current detecting device

Abstract

An embodiment of the invention discloses a leakage current detecting device. The device comprises an intermediate tap of a secondary winding of an isolation transformer, a thermistor PTC, a leakage current sampling resistor R2, a regulating resistor R1, a bidirectional transient voltage suppressor (TVS), a filter capacitor C1 and a bidirectional optocoupler U1. The first end of the bidirectional transient voltage suppressor (TVS) is electrically connected to the intermediate tap of the secondary winding of the isolation transformer, and the bidirectional transient voltage suppressor (TVS) is connected in series with the thermistor and grounded. The regulating resistor R1 is connected in series with the leakage current sampling resistor R2 and then connected in parallel with the bidirectional transient voltage suppressor (TVS), the second end of the filter capacitor C1 is electrically connected to the second end of the leakage current sampling resistor R2, the primary side of the bidirectional optocoupler U1 is connected to the filter capacitor C1 in parallel, and the secondary side of the bidirectional optocoupler U1 generates a detection signal. The leakage current detecting device has the advantages of low cost, simple solution, few devices, simple solution and high reliability.

Description

technical field [0001] The invention relates to the technical field of elevators, in particular to a leakage current detection device. Background technique [0002] On the one hand, in many old elevators, due to the long-term use of the brake coil and the aging of the coil, the insulation function is reduced, and there may be a fault phenomenon that the coil leaks to the earth PE; and when the leakage current does not reach the brake circuit When controlling the operating current of the air switch (generally 30mA, or the control air switch is faulty), the control air switch will not trip, which will further cause the elevator to drag the brakes or slip, resulting in safety hazards. [0003] figure 1 It is a schematic diagram of an elevator brake power supply circuit in the prior art. refer to figure 1 , the existing brake power supply circuit 100 includes a brake power supply circuit 11 , a freewheeling circuit 12 , and a brake coil 13 . During normal operation, when the...

AI Technical Summary

Problems solved by technology

The current on the two coils of the brake coil will be unbalanced. For example, in the first half cycle of AC: only the upper half of the coil at point M on L2 has current. This working method will cause the brake coils L1 and L2 to be out of sync, that is, one In the AC cycle, when L1 works through two wave currents, only a part of L2 works

When the elevator is running, it will cause the elevator to drag the brakes; when the elevator stops, when L2 continues to flow through the leakage point without passing through the freewheeling circuit, it will cause the brake to open a small gap and cause the elevator to slip.

Therefore, there is a need for a detection circuit and detection method that can solve the above problems. Because the existing detection methods in the market are basically realized by Hall sensors detecting the current between the brake coil and the earth and converting it into a voltage signal, the method is complicated and high cost

Images