HYUNDAI has developed a digital variable voltage and frequency inverter to control the slipping of wheels with parallel traction motors.

Wheel slippage can lead to increased engine speed, generating more power and resulting in over-voltage in the induction motor. Voltage detection systems can be used to trigger power reduction, but these are not always successful.

The Hyundai VVVF converts a 1·5 kVDC supply to power three-phase traction motors, and operates in reverse during dynamic braking. Using a high-speed 32 bit signal processor, the VVVF inverter instantaneously reduces the RMS current without torque loss. This gives improved control of the wheel adhesion, reducing the jerk often felt by passengers.

The controller offers multi-processing functionality, self diagnostics, fault tolerance and a digital display. It has a simple integrated structure with a high-capacity 3300V/1200A IGBT with intelligent drive. The weight is reduced by 40% and noise by 65% compared to equivalent electro-mechanical devices; it can cost 60% less.

Hyundai Heavy Industries, South Korea

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