A High-Efficiency Motor-Drive Architecture with Direct AC-AC Conversion
Somasundaram Essakiappan, R&D Engineering Manager, QM Power Inc.


A high-efficiency motor-drive architecture with direct ac-ac conversion has been developed for Heating, Ventilation and Air-Conditioning (HVAC), industrial drives, and commercial/residential applications.  The motor-drive, which eliminates the dc-link in traditional motor drives, can operate motors with a wide variety of power range: fractional horse-power single-phase motors to high power three-phase motors; and different types including induction and permanent magnet synchronous motors. Q-Sync utilizes Pulse Width Modulation (PWM) only below the synchronous or rated speed, during start-up and shut-down, and it connects the motor directly to the line voltage once the motor reaches the rated speed. In a three-phase implementation, it also uses 33% fewer power semiconductor devices, while retaining key functionality and performance. These innovations lead to high operational efficiency of the integrated motor and drive system, due in large part to the reduced losses in power electronics.  In addition, since no dc-link capacitor is required, a very compact and highly reliable implementation has been realized. The presentation will describe the Q-Sync concept, operating principles, a representative performance analysis and corresponding hardware operation data. Engineers in the industry will benefit from understanding the concept’s objectives and development, as metrics like efficiency and compactness are highly desired.