Variable structure bridge/half-bridge electronic commutator for PM BLDC motor supply

A novel drive system consisting of PM BLDC motor and variable bridge/half-bridge structure electronic commutator is discussed in the paper. This kind of drive is recommended in case of battery supply, if there is no possibility of raising the supply voltage. Structure of the drive is presented and its analysis is conducted. The innovative structure makes possible the increase of motor's idle speed and hence motor's operating range is enlarged. The adverse effects of the operation at negative EMFs have been pointed out; they make impossible the direct switching of the commutator from bridge configuration to half-bridge configuration. The significant reduction in these perturbations has been achieved by using three extra switching devices and capacitor buffer connected in accordance with authors' suggestions. Examples of simulation results and laboratory tests have been included in paper in order to illustrate the operation of the designed drive system.