Patented inverter `boosts low-speed performance`

Chorus Motors, the Gibraltar-based developer of the novel multi-phase Meshcon motor-drive, has been awarded a US patent for a low-cost PWM (pulse width modulation) drive, said to boost overload capacities at low speeds.

The patent describes a technique for adding a range of harmonics to the output waveform of an inverter to increase its output voltage capacity. The harmonics can also be used to adjust the current waveform feeding the motor, thus boosting the inverter`s current output capability.

The extra voltage capacity can be used in various ways, including making the rotor turn faster. By winding a motor with extra series turns, it can convert the additional voltage into extra torque at low speeds.

Alternatively, if the inverter forms part of a generator system, a higher current output can be obtained by synthesizing its voltage waveform.

Instead of obtaining more speed or current, the increased voltage can allow a smaller inverter to be used than normal, thus saving costs and space. Chorus claims that for traction and start-stop motor applications, drive costs can be cut by 60% without losing performance compared to conventional drives of a similar size. Most of the savings come from the lower costs of the power semiconductors in the new design.

Stuart Harbron, Chorus Motors` chief patent officer, says that with the new design, "electric motor technology is making the next leap forward". He adds that the Chorus Meshcon technology "is the ideal partner for the forward-looking designers seeking to break out of the straitjacket of traditional motor design, and to make full use of the power that has always been available — and to do it all with much healthier profit margins.