Motor protection relay / Multi protection relay PRS-1S

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The PRS-1S is an electronic motor protection relay with high functionality that detects various states when an AC motor starts and while it is operating. Measurement and monitoring functions are installed in addition to the basic 3 elements of the motor protection function (overload protection, open-phase protection, and reverse-phase protection).

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1.Overload protection function

The protection function is adapted to the motor starting characteristics and the load characteristics.

2.Open-phase protection function

"Open phase" is a state in which the motor operated in a single-phase state because the power wire connected to the motor became disconnected, the connection area was loose, or there was a disconnection inside the motor. Open-phase states can cause motor winding burnout, and detecting open-phase states can prevent this.

3.Reverse-phase protection function

"Reverse-phase" is a state in which the phase sequence of a motor is connected in reverse and the motor rotates in the reverse direction. This cannot be checked visually in some installation locations, and reverse-phase protection is a function that is essential in order to prevent reverse rotation.

4.Other protection functions

  • Maximum starting time detection: Measures the time it takes to return to steady-state operation after the motor starts. If the set time is exceeded,   the protection function activates and prevents the motor from the operation at high speeds.
  • Unbalanced current protection: Detects unbalanced current, which can cause the motor to heat up and burn out and protects the motor.
  • Undercurrent protection: Activates when a current decrease is detected in the electrical circuit. The objective of this protection function is to detect light loads and disconnections.
  • Motor winding temperature monitoring: This function monitors the motor winding temperature. The temperature sensor signal provided near the winding area is incorporated into the circuit inside the relay, and monitors the temperature (the temperature measurement range is 0-250℃ ).

5.Function that displays and saves the activation information and history

  • Trip and alarm activation: If trip or alarm occurs, the time of occurrence, cause of activation, activation value, and activation duration are displayed on the screen. The system can save 100 instances each of trip and alarm activation.
  • History of phenomena that occurred: The system can save a total of 200 instances of the history of the following phenomena that occurred. These phenomena will be displayed on the screen in chronological order, so it is easy to track detailed information about the phenomena that occurred.
    • Trip activation (time of occurrence / cause of activation)
    • Alarm activation (time of occurrence / cause of activation)
    • Reset operation (time of occurrence / reset operation details)
    • External input (time of occurrence / external input state)

6.Measurement display function

  • The display screen displays the following measurement values.
    • Phase current
    • Unbalanced current
    • Motor winding temperature
    • Motor load current
    • Leakage current
    • Motor starting time
    • Motor starting current
    • Motor operating time
    • Motor operating cycles
    • External command input state
    • External output operating state

7.Monitoring function

  • Communication function: In Modbus RTU mode (RS-485), it is possible to read and write protection setting values and output   measurement values and histories.
  • Analog output: The maximum phase current value can be converted to 4-20 mA current and output externally.

General specifications

Control voltage DC110V
VA consumption 5VA
Temperature range -10℃~ +55℃
Storage temperature -25℃~ +75℃
Based standard IEC60255 : Measuring relays and protection equipment
IEC60947-4-1 Part 4: Contactors and Motor-Starters
Protective function Overload protection/Open-phase protection/Reverse-phase protection/Maximum starting time detection/Unbalanced current protection/Undercurrent protection
Measurement function Phase current/Unbalanced current/Motor winding temperature/Motor load current/Leakage current
Motor starting time/Motor starting current/Motor operating time/Motor operating cycles
External command input state/External output operating state
Display function Trip and alarm activation/History of phenomena that occurred(Trip activation, Alarm activation, Reset operation and External input)
Monitoring function Monitoring of Motor winding temperatire
Communication function Optional : Modbus RTU(RS-485)
Outline dimensions (WxHxD) [mm] 96x144x116