Vacon AC drives reduce harmonics to non-issue

Vacon offers a new type of AC drive with an active front-end (active input bridge) technology that dramatically reduces the harmonic content in the power supply

Vacon offers a new type of AC drive with an active front-end (active input bridge) technology that dramatically reduces the harmonic content in the power supply.

Vacon is the world's first supplier to offer a complete series of regenerative AC drives ranging from 2.2 kW to 3000 kW in the voltage range from 380 V to 690 V AC.

Today, the majority of the AC drives are equipped with a 6-pulse diode bridge rectifier.

Its output voltage is determined by the supply voltage, and the energy flows in one direction only.

Although robust, the rectifier generates high levels of harmonic distortion in the supply.

Typically, a correctly sized AC choke can reduce the total current distortion (THD) to about 30%.

Without the choke, current distortion values of over 70% are not uncommon.

In contrast, current distortion values less than 4% can be easily achieved with the Vacon new active front-end technology.

Even with weak supplies (generators), this results in a total harmonic voltage distortion of less than 3%.

The most stringent requirement in any of the relevant standards is THDU 5%.

The low harmonic distortion of the supply power also contributes to a significantly lower supply current.

As a result, fuses, supply cables and supply transformers can be kept small, and thus considerable savings may be achieved.

The active front end uses a higher intermediate DC voltage.

Therefore, the voltage supplied to the motor can be increased above the rated supply voltage.

With a 400 V supply, for instance, it is possible to supply a 500 V output voltage to the motor, which results in lower output currents, lower cable voltage losses or a 20-25% higher motor power.

In weak networks, such as those on ships, it is essential to keep the harmonic content in the power supply as low as possible.

Vacon regenerative AC drives are not only capable of producing a very low level of harmonic distortion, but also transferring the braking power back to the supply.

Feeding energy back to the grid opens new possibilities for the use of inverters.

On ships, this requires sufficient load.

The regenerative solution is ideal in typical braking situations (eg winches, cranes) where energy is otherwise wasted in a braking resistor as the load tries to rotate the motor.

The Vacon solution allows sizing of generators, switches, cables etc on the ship according to the real need, and all the sensitive equipment will work without being disturbed.

The power factor compensation, usually done by capacitors or synchronous generators, can be done by the drive.

The regenerative technology is also well suited for new environmentally friendly applications such as solar panels, windmills with variable rotor speeds and fuel cells.

Vacon Group was founded in 1993 for one purpose only: to create, develop and provide AC drives worldwide.

Ambitious to meet the most demanding needs of clients seeking top performance, ease of use and reliability, Vacon offers AC drives in the power range of 0.25 kW to 3 MW.

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