Libratherm Instruments Pvt. Ltd.
Libratherm Instruments Pvt. Ltd.
Dahisar East, Mumbai, Maharashtra

Motor Soft Starter SCR Firing Card

Three phase SCR triggering card for AC Induction motor soft starter

Motor Soft Starter SCR Ciring Card

Motor Soft Starter SCR Ciring Card
  • Motor Soft Starter SCR Ciring Card
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Product Details:

ApplicationAC Induction motor
Current Flow25 Amps to 1000 Amps
Motor Power25 Amps to 1000 Amps
User selectable configurationFor 3 wire close delta, 6 wire open delta

Product Description:
To gradually accelerate the speed of AC 3 phase induction motor it is required to feed increasing voltage to the motor and such behaviour is only possible by connecting SCRs in series with the motor. The SCRs are controlled by MSST-15 card to generate the firing pulses giving the effect of soft start. Libratherm offers SCR triggering card model MSST-15, which is specially designed for motor soft starter application. This card accepts the start command from a switch contact and generates gate-cathode pulses for 3 pairs of back to back connected SCRs. The user has access to set the starting voltage to create the torque and to set the soft start time. The card takes the feedback from 5A CT to monitor the load current and to generate the trip contact in case of over load condition. Once the motor achieves full RPM, it is not required to pass the current through the SCRs and hence these SCRs can be by passed using an external contactor. The bypass command is generated by MSST-15, once the full speed is achieved as indicated by TOR LED.

The MSST-15 card works on Auxilary supply of 230VAC and three phase line synchronisation is done through the load lines. The user can build motor soft starter just by using the MSST-15 card and suitable ratings of external thyristors, based on the motor capacity.


  • User settable jump start and soft start/ramp time
  • Accepts start and stop command from external potential free contact
  • Current Limit and Overload trip facility
  • Contactor bypass output and Fault output

Additional Information:

  • Item Code: MSST-15
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Kamlesh Panchal (CEO)
No. 401-403, Diamond Industrial Estate, Ketki Pada Road Dahisar East
Mumbai- 400068, Maharashtra, India

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