Motor drive harnesses matrix convertor technology

Yaskawa Electric has won a global technology race and unveiled the world's first variable speed AC motor control to use matrix convertor technology.

Yaskawa Electric has won a global technology race and unveiled the world's first variable speed AC motor control to use matrix convertor technology.

How to develop a practical matrix convertor has puzzled universities, academic research establishments and variable speed drive manufacturers internationally for years.

The benefits of the technology include minimal generation of harmonics, regenerative braking without the need for additional resistors, automatic return of energy to the supply during braking and enhanced operating life.

Matrix-convertor drives, which offer efficient operation in all four quadrants, differ radically from VSDs in common use today.

Ordinary drives convert the incoming AC supply to DC, and then convert the DC back to AC at the required frequency and voltage.

In contrast, Yaskawa's matrix convertor drives use an array of semiconductor switches - packaged insulated gate bipolar transistors (IGBTs) - to connect the three phases of the supply directly to the motor in a precisely timed sequence.

This method of operation reduces harmonic generation to approximately 8% of the level associated with conventional drives, while also offering almost unity power factor - that is, no wasted energy.

The elimination of the DC-bridge section of the drive makes it easy to arrange for energy to be returned to the supply during braking, and also removes the need for energy-wasting, heat-generating braking resistors.

A further benefit is that the new drives need no large electrolytic capacitors.

As the unavoidable deterioration of these capacitors is the principle life-limiting factor in most modern electronic equipment, their elimination boosts both drive reliability and lifespan.

Initially, Yaskawa's new matrix convertor drives will cost more than conventional counterparts.

They are, however, expected to be an attractive option for applications such as lifts, cranes and presses where their efficient regeneration is a particular benefit, and in sensitive environments, such as hospitals and computer centre installations, where it is essential to keep supply harmonics to a minimum.

The new drives, which could be available by the middle of next year, will initially be supplied in three-phase 400V versions with ratings from 5.5 to 22kW.

Yaskawa plans to extend this range up to 75kW, and also to introduce 200V models with ratings from 5.5 to 45kW.

Yaskawa Electric is the world's largest manufacturer of variable speed drives and has a history of pioneering developments in motors and motor control technology.

It produced some of the first DC servomotors in the 1950s; introduced a minicomputer based CNC system in the 1960s; the first ever vector controlled inverters in the 1970s; the first PWM inverter in the 1980s; and the world's first sensorless flux vector inverter in the 1990s.

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