Medium voltage inverter

Paul Boughton

Mitsubishi Electric’s new range of innovative medium voltage inverter drives are designed for both the current and future energy needs of industry.

The drives are compact and modular, allowing for flexible installation in confined areas and deliver industry-leading energy efficiency with advanced IGBTs (Insulated-Gate Bipolar transistors). With regenerative braking available as standard, they offer high levels of customer value in many applications.

Faced with the challenges of ensuring long-term reliability while improving energy efficiency, medium voltage inverters have previously been fixed with a rigid cabinet layout. The flexible construction of the MVe2 now offers simple solutions for customer applications, ensuring high levels of energy efficiency in operation, and also being easy to install, commission and maintain. In particular, the 10/11kV drives have a direct 10/11kV motor feed, immediately removing the need for the transformer found in competitor products. They are a common development by Toshiba and Mitsubishi Electric Corporation (TMEIC), based on decades of experience in the production of medium voltage inverters.

The MVe2 has a very small footprint. This is very significant because suitable installation space is often very limited in the industries where the range is to be deployed. Aware of this, the design team applied some original thought processes and developed a separately locatable front end transformer section. This uses just a few cables to connect the inverter, enabling it to be positioned in a more convenient location.

The designers also ensured that, unlike many other medium voltage inverters, the MVe2 has a lower head room requirement, allowing it to fit comfortably into a standard shipping container. This ensures safe and economical transportation to site, compared to taller inverters that must be individually sealed against the weather for transportation with special arrangements being made by the freight company to allow for the extra height during the journey.

The modular concept of the MVe2’s design is carried through to the inverter stages, generating the further benefit that it can be specified for use with motors of different voltages, allowing them to be connected to the same MV system, even when the voltages do not match – without the requirement for an additional external transformer installation.

Long-life, maintenance-free film capacitors (rather than conventional electrolyte capacitors) are used for the intermediate circuit and the ventilation fan has also been designed for extended operation. This means that servicing is reduced to once around every seven years, rather than the more customary three years. Further enhancing the energy efficiency, regenerative braking comes as standard, whilst the sensorless vector control feature gives fast response, stable operation and capabilities for rapid acceleration and deceleration.