THP type three-phase missing (wrong phase) protection board

I. Overview
THP type three-phase open-phase (wrong-phase) protection board is specially designed for three-phase unbalanced faults caused by three-phase power loss or wrong phase. It is based on the national "Eighth Five-Year Plan" Achievement-TH201 special three-phase phase loss or phase error protection thick film integrated circuit is the core, and it is made with high-quality resistors and other electronic components. Its main design features are as follows:
1. It is allowed to directly apply three-phase 380V or three-phase 30V, so it can be applied to the occasions where the user system has a three-phase power transformer or does not have a three-phase power transformer.
2. The working power supply voltage can be three-phase AC 8V or single-phase AC 18V.
3. When the three-phase power supply does not lack phase or the phase sequence is normal, the green light-emitting diode inside the board lights up, and when the three-phase power supply lacks phase or the phase sequence is wrong, the red light-emitting diode inside the board lights up, and gives a high for blocking the external circuit. Level or low level signal, while the relay located in the board acts, and its normally closed contact can be used to break the main circuit of the user system.
4. Two connectors are used for external connection, one for strong current and the other for weak current, which meets the needs of different users.
5. It can be conveniently used for three-phase phase sequence detection, wrong phase or lack of phase alarm, so it can be applied to the protection of three-phase AC motors, and can be widely used for phase sequence monitoring and protection in all industrial fields that use three-phase AC power.
II. How to use
THP type three-phase phase loss (wrong phase) protection board printed board dimensions are lengthwidthheight=100mm70mm40mm, and its component arrangement is shown in Figure 1. It can be seen from the figure that there are two connectors for the external connection of the THP board. The three AC 8V in the plug-in S1 are connected to the secondary side of the three-phase power transformer. The current drawn from the power supply is 30mA. The working power supply can also be connected as a pair. The secondary side of a single-phase power transformer with a side voltage of AC 18V, the current drawn from the power supply is 50mA, when the user system is designed with a step-down transformer, the a, b, c and GND in the plug-in S1 are respectively connected to the secondary side voltage It is the secondary side of the 30V three-phase power transformer. The secondary side of the transformer should be in star connection, and its neutral point should be connected to GND. At this time, A, B, C, and O in the connector S2 are not connected to any signal, and they are suspended. , The remaining L1 and L2 are the signals provided to the user after the protection, L1 is high after the protection action, and is low during normal; while L2 is the low level after the protection action, and normally under normal working conditions. It is high level. The A, B, C, O in the plug-in S2 are used when there is no step-down transformer in the user system, and the AC three-phase 380V input is used to directly detect the phase sequence when the phase is missing or out of phase protection. When connecting to the grid A, B, C three-phase voltage Input, here O is the three-phase power grid neutral line connection terminal (at this time the a, b, c, GND in socket S1 should be suspended and not connected), plug-in S2 has a normally closed contact connection terminal between A# and B#, The contact capacity is 380V/0.5A or 220V/1A, which is used to break the main circuit of the user system when a fault occurs.


Figure 1
Three practical examples
Figure 2 shows the working principle diagram of the THP type protection board used in the phase loss protection circuit of the three-phase AC motor. In the picture, JZ is the main contactor.


Figure 2