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Multi-frequency MV starter doubles starting torques

03 January, 2014

A Chinese specialist in MV (medium voltage) drives and power electronics has developed a new MV motor starter technology that, it says, can double starting torques, dramatically reduce starting currents, and save space and weight compared to conventional MV motor starting technologies.

RXPE’s patented MFS (multi-frequency starter) system combines elements of VSDs with conventional MV starter technologies. Instead of operating at a single fixed frequency, it switches through up to three frequencies (12.5, 25 and 50Hz) when starting a motor.

This has several claimed benefits. First, it can deliver starting torques of 80­–90%, compared 30–40% for typical conventional MV starters.

Second, starting currents with the new system are typically about double the rated current, compared to four to fives times the rated current for conventional starters. This in turn, means that smaller, less costly peripheral components can be used.

And third, the footprint and the weight of the MFS system are typically about 30% less than comparable conventional systems.

RXPE claims that the system also reduces energy consumption, site voltage fluctuations and water hammer (in pumping applications). It says that the MFS is the only real alternative to MV VSDs for soft-starting heavy loads to run at full speed, adding that it can handle applications that would normally be difficult for a soft-starter.

RXPE claims that its multi-frequency MV starter offers many advantages

The MFS system, which can start up to four motors, covers the power range 160kW–50MW and the voltage range 2.3–13.8kV. The starters are available with or without bypass contactors, and incorporate four pump-starting curves as standard. The starting currents can be chosen by the user.

The table below compares the MFS system with other MV starting technologies.

The MFS technology is being sold and supported in Europe by UK-based Severn Drives & Energy. Its director Jonathan Jones expects the main markets for the MFS to be the water, power, and oil and gas industries.

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