Protection of the motor by phase pulse phase phasing

PESD1CAN electrostatic protection SOT23-3 24V two-way

5V, 35pF, bidirectional ESD protection diode

The electrical connection diagram of the three-phase asynchronous motor is shown in the figure, and the dotted line in the figure is the circuit diagram of the protector shown in the figure below. The upper right picture shows the current waveform of the three-phase motor and the pulse waveform of the current transformer. It can be seen from the figure that the phase current in normal operation is a symmetric wave (or vector) with a phase difference of φ1=φ2=φ3=120°, and the zero-crossing detection pulse in the pulse transformer is evenly distributed, and the time isolation is 6.6 ms. In phase, the symmetry of the current waveform is broken, and the interval between the zero-crossing detection pulses is between 6.6 and 10 ms. Using this difference, the 555 trigger circuit, the one-shot delay circuit and the relay control circuit are designed to perform phase-failure protection.
IC1 and VT1, C2, Rl, RP1 form a monostable trigger circuit, so that the charging time of T2 is tdl=1.1(R.1+RP1)C2<6.6ms, that is, the charging voltage of C2 is not charged to 1/3VDD. Before the flat, due to the 9.6ms interval zero-crossing pulse, the VT1 discharge, so IC1 can not be set, so the IC1 pin 3 is low during normal operation, so that the IC2 monostable delay circuit is in the forced reset state ( 4 feet are low level), J does not move, LED does not light. When the stator winding of the motor is broken or disconnected, the zero-crossing detection pulse interval is increased. When the 2 pin of ICl reaches 1/3Vdd, the setting is reversed, the reset state of IC2 is released, IC2 is set, and J is closed. The motor is powered off.