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RMU Test System
The Ring Main Unit (RMU) Test System is designed to test RMUs of all ratings as per IEC standards for routine tests and final acceptance. The system capable of carrying out measurements for both manually operated and electrically operated RMUs.

The left & right hand switches of RMU are usually manually operated switches. During the test, the system captures data automatically by an innovative data capturing technique.

In case of motorised or coil-based switches, the motor or coil is operated through the system, and the current initiation in the motor or coil is used as an initiation for data capture. Similar method is used for testing a Circuit Breaker.

Analysis of test results provides information which is useful for evaluating and rectifying settings for contact non-simultaneity, closing and opening speeds, over-travel, rebound and contact wipe. The tests that can be conducted by this test system are Close & Open.


  • Simultaneity of contacts
  • Bounce
  • Travel characteristics of contact for speed, contact gap, over-travel and rebound
  • Trip & Close Coil current characteristics
  • Switch Timings
  • Motor Current
  • Spring Charging Time
  • Static Contact Resistance of all switches (using MVT 100)


  • Connects to RMUs with wear resistant test leads, having quick-fit connectors
  • Selects pre-programmed setup parameters and pass/fail limits through software.
  • Prints results in a graphical format with test header and calculation footer, on external printer


  • Windows based Test Manager Software allows storing test setups, viewing reports, and analyzing and handling graphical test data using a PC
  • Easy-to-use, high level Graphical User Interface and programmable test plans facilitate to create a test setup library
  • It performs all tests and compares each parameter with Pass/Fail limits to declare the RMU as OK or FAIL
  • Test certificate can be stored and printed as per the manufacturer’s format
  • All test data is stored in a database for analysis

Models Offered

  • The RMU Test System is offered in two variants, AutoScan DIN 41494 rack version & AutoScan Work-Table version.
  • The AutoScan Rack version, along with accessories like programmable power supplies are expandable to meet future needs of the manufacturer.
  • AutoScan Work-Table version is an ergonomic arrangement of measuring hardware and control PC to help better utilization of space on the shop floor.
  • AutoScan Trolley version is a compact arrangement of measuring hardware on a movable trolley for easy movement on the shop floor.



C & S Electric


Crompton & Greaves