Constant-frequency multi-resonant converter-fed DC motor drives

Low-inductance DC motors with high power density and low rotor inertia are becoming more attractive, particularly for servo applications. In order to maintain their current ripples within acceptable levels, power converters need to operate at high switching frequencies. However, the increase in switching frequencies realizable by hard-switching techniques accompanies the increase in switching losses and switching stresses. In this paper, soft-switching DC-DC converters are discussed for application to DC motor drives. The most feasible one, namely the zero-voltage-switching (ZVS) constant frequency multi-resonant converter (CF-MRC), has been identified to be appropriate for DC motor drives. This soft-switching converter not only possesses the advantages of achieving high switching frequencies with practically zero switching losses and eliminating variable-frequency operation, but also provides full ranges of voltage conversion and load variation. A ZVS-CF-MRC-fed DC motor drive has been prototyped and tested. Experimental results verify the successful application of the ZVS-CF-MRC to DC motor drives, which takes definite advantages of high efficiency, small current ripples and minimum switching stresses