Reduce the number of sliding contact wires to reduce the failure rate of electric hoists. Using a sliding wire to complete two action processes:

1. Working principle

When there is no voltage on the sliding wire H1, due to the fact that the original side of transformers TR1 and TR2 have the same name end, while the secondary side has the opposite name end, there is no voltage on both ends of the J1 coil of the intermediate relay, and the contactors ZC and FC do not operate. When the J2 contact of the intermediate relay is closed (J3 is not closed), the sliding contact line H1 is the R-phase voltage, while TR1 has no voltage output on the secondary side due to the same R-phase voltage at both ends of the primary side. The TR2 primary side has a voltage of 380V for R and S phases, and J1 is energized and pulled in. Due to the same R-phase voltage at both ends of the contactor ZC, it cannot be closed; The voltage at both ends of the contactor FC is 380V for R and S phases, and the contactor FC is pulled in to complete the lowering action.

Similarly, when J3 is engaged (J2 is not engaged), contactor ZC is engaged to complete the upward movement.

2. Parameter selection of electrical components

Transformers TR1 and TR2 should be standard control transformers. Considering the small capacity of the intermediate relay coil, the transformer capacity should be 1.5 to 2 times the capacity of the online coil.

Considering that there must be a certain voltage drop on the secondary side of transformers TR1 and TR2, a transformer with a larger turn ratio should be selected to reduce the impedance of the secondary side of the transformer. Generally, 380V/24V and 380V/36V are preferred.

In the design of electric hoists, any two signals that do not require simultaneous action can be achieved using the principle of phase difference at the same end of the transformer, which reduces the number of sliding wires and reduces the fault rate. This method has been applied to electric hoists, running normally and achieving significant results.

Since the problem has been presented, it must be resolved reasonably and correctly. Through many experiments, reducing the number of sliding contact wires is used to reduce the failure rate of electric hoists. It is feasible to use a sliding contact wire to complete the two action processes.

Method 1 Operation principle:

1. Due to the same R-phase voltage at both ends of the contactor ZC, it cannot be closed; The voltage at both ends of the contactor FC is 380V for R and S phases, and the contactor FC is pulled in to complete the lowering action. Similarly, when J3 is engaged (J2 is not engaged), contactor ZC is engaged to complete the lifting action.

2. When there is no voltage on the sliding contact wire H1, the contactors ZC and FC do not take action because the original side of transformers TR1 and TR2 have the same name end and the secondary side has the opposite name end. There is no voltage on both ends of the central relay J1 coil.

3. When the J2 contact of the central relay is closed (J3 is not closed), the sliding contact line H1 is the R-phase voltage, while TR1 has no voltage output on the secondary side due to the same R-phase voltage on both ends of the primary side. The TR2 primary side has a voltage of 380V for R and S phases, and J1 is energized and pulled in.

Method 2: Selection of Electrical Component Parameters:

1. Considering that there must be a certain voltage drop on the secondary side of transformers TR1 and TR2, a transformer with a larger turn ratio should be selected when selecting the transformer to reduce the impedance of the secondary side. Usually, 380V/24V and 380V/36V are preferred.

2. Transformers TR1 and TR2 should be operated according to regulations. Considering the small capacity of the central relay coil, the transformer capacity should be 1.5 to 2 times the capacity of the online coil.