PSM 642U Motor Protection Measurement and Control Device

Guodian Nanjing Automation PSM-642U Motor Protection and Control Device

Scope of Application
The PSM 642U Motor Protection and Control Device is a comprehensive multifunctional integrated unit that provides complete protection against phase-to-phase faults, ground faults, and abnormal operating conditions for motors, while incorporating various measurement and control functions. It can be applied to various traditionally contactor or circuit breaker-controlled 3-10kV AC high-voltage large and medium-sized motors. Its application fields cover industries such as power, water conservancy, transportation, petroleum, chemical, coal, metallurgy, and more.

Protection Measurement and Control

a. Measurement quantities such as current, voltage, power, power factor, etc.

b. 14 external switch input telemetry collection

c. Circuit breaker position, manual tripping, and accident telemetry

d. Normal circuit breaker opening and closing

e. GPS time synchronization input

Protection Functions and Principles

Motor Starting

When the control word KG2.14=0, the device determines the motor starting time as Min (Tstart, Tstart0). Here, Tstart is the actual starting time of this instance, which refers to the time elapsed from the moment the phase current suddenly changes from zero to 10%In (T0) until the current drops to 120%In after passing the peak (In is the motor rated current, the same applies below). Tstart0 is the "motor starting time setting," representing the time from zero speed to rated speed, which can be set to 1.2 times the maximum starting time of the motor.

When the control word KG2.14=1, the device fixes the motor starting time to Tstart0, with the timing starting at T0.

The device defines a soft压板灯 (green LED light) on the panel as the motor starting time indicator, which remains lit during the motor starting process to visually indicate the motor's starting phase. Prolonged starting time can cause rotor heating, endangering the motor's normal operation. The long starting protection function can be enabled or disabled via the soft压板. This protection is only active during motor starting. During the starting process, if any phase current exceeds the set current for the set duration, the long starting protection triggers the output, with the action indicator being a signal light (red LED light) on the panel. After the motor starting process ends, the protection automatically disables.

For a motor operating normally, if the supply bus voltage suddenly disappears or significantly drops and then恢复正常 within a short time, the motor will self-accelerate and return to normal operation. This process is called motor self-starting. When the bus voltage rises abruptly after being below 75% of the rated voltage and any phase current exceeds 120%In, the device identifies the beginning of the motor self-starting process. The device handles the self-starting process in the same manner as the starting process.