Capacitor Switching Solutions

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Automatic Power Factor Control (APFC) panels are the ideal solution for Reactive Power Management in industries to improve the power factor and reduce the electricity bills. However, switching of capacitor banks is a challenging task in the APFC panels because of the high inrush current and voltage transients initiated by capacitors at the time of switching. The selection of an appropriate switching device is, therefore, vital and depends on the ability to carry rated capacitor current continuously while withstanding the peak inrush current of the capacitor.

L&T Electrical & Automation (E&A) understands the need for switching and offers a complete range of capacitor switching solutions including Capacitor Duty Contactors and Thyristor Switching Modules. In most panel installations, multiple-stage capacitor banks are used as steps of unequal ratings. The bigger steps of higher kVAr ratings are switched on initially whereas smaller steps are switched on periodically to achieve the target PF.

Our Capacitor Duty Capacitors are designed for switching of bigger steps where the frequency of switching is less and the load fluctuation is not very high. Thyristor Switching Modules are used especially for switching smaller rating capacitors or when load fluctuation is heavy. Rapid Switching (5 ms to 20 ms) is possible with Thyristor Switching Module.

Capacitor Duty Contactor – MO C

L&T Electrical & Automation (E&A) Capacitor Duty Contactors are specially designed for capacitor switching applications. As capacitor switching is associated with high inrush current, the contactors are provided with damping resistors which limit the value of inrush current to a safe value. The contactors are used in APFC panels for switching power capacitors. The selection of these capacitors depends on the amount of reactive power compensation required.

MO C range of capacitor switching contactors has a patented mechanism that disconnects the early make auxiliary contacts after the main contacts are closed. This eliminates the possibility of auxiliary contacts carrying and breaking the currents during braking operations. This enhances the product switching performance and improves the product life.


  • Available for capacitor range from 3 – 100 kVAr
  • Separately terminated de-latching contacts for enhanced operational reliability
  • Improved Switching Performance
  • Dual contact gap for De-Latching Auxiliary Contacts ensuring higher electrical life
  • Modular Design saving precious panel space
  • Separate termination of damping resistors
  • Encapsulated resistor assembly ensuring safety
  • Inbuilt surge suppressor with the coil
  • Wide & chatter-free operating band
  • Lugless Termination

Thyristor Switching Module

With the thyristor module, we provide the main component – ‘The Electronic Switch’- for dynamic power factor correction. The TSM series offers fast electronically controlled, self-observing thyristor switches for capacitive loads up to 50 kVAr that are capable to switch PFC capacitors within a few milliseconds nearly without a limitation to the number of switching during the capacitor lifetime. These switching modules are easy to install, have a fast reaction time of 5 msec and come with built-in indications of operations, faults and activation. These thyristor modules are very compact and operate at lower power losses.


  • Faster response time (5 ms)
  • High peak inverse voltage (2.2 kV) ensures long operational life
  • Automatic thermal cut-off
  • Monitoring of voltage, phase sequence, faults; display of status via LED
  • No system perturbation caused by switching operations (no transients)
  • No auxiliary supply needed
  • Maintenance-free
  • No noise during switching
  • Compact design ready for connection and easy installation