Medium voltage drives claim 99% efficiency

Edited by the Engineeringtalk editorial team Nov 20, 2006

MVW-01 drives are voltage source inverters employing the latest multiprocessor control architecture.

WEG's new MVW-01 range is setting new benchmarks for medium voltage (MV) drive efficiency, achieving 99% with a new design that employs multilevel topology to minimise component levels, and high voltage (6.5kV) IBGTs to reduce motor harmonic currents to extremely low levels.

The introduction of the MVW-01 drives means that WEG is the only supplier of medium voltage speed variation systems that can offer a total package, including input switchgear, dry or oil-filled phase-shifting transformer, variable speed drive (VSD) and medium voltage motor.

Unlike many MV drives on the market, which have three- or five-layer control, the WEG MVW-01 range has just two layers.

The benefit of this is a reduction in the number of components in the drive, and commensurate improvements in efficiency and reliability.

With energy costs at record levels, the efficiency performance of the MVW-01 drives is all-important.

It has been calculated that for every 1% of efficiency lost on 1MW drives, the user will pay an extra GBP 5000 per year on running costs - and that figure is just for the drive alone.

The MVW-01 drives are voltage source inverters (VSI) employing the latest multiprocessor control architecture.

They integrate a 32bit high-performance processor (64bit bus) with floating point capability to provide high-performance control of MV motors in the voltage range from 2.3 to 4.16kV, and in the power range up to 3355kW.

The MVW-01 drives are an ideal complement to WEG's H Line of MV motors, which cater for outputs to 3150kW and voltages up to 6600V (50 or 60Hz).

Like the MVW-01 drives, the H Line motors are compact and extremely robust machines, ideally suited to operating conditions encountered in the most arduous industrial applications.

Housed in compact IP41/NEMA 1 enclosures, the MVW-01 drives offer users the convenience and cost saving benefits of air cooling.

They are configured for 12-pulse operation, with 18-pulse available on request.

These ensure excellent voltage waveforms for the drives, and result in a high power factor (greater than 0.95) that fully meets the requirements of G5/4 and IEEE519.

The MVW-01 drives deliver high levels of reliability and low noise levels (greater than 75dBa) with a design that offers a number of key features: it includes the latest generation of high voltage (6.5kV) IBGTs; provides optical isolation between the control section and the high voltage sections of the drives; and employs ultrareliable dry-type plastic film power capacitors.

In addition, the design also includes withdrawable power arms for fast and simple maintenance.

Contradicting the mantra that MV drives are difficult to use, the MVW-01 units follow the same simplified programming structure as WEG's LV drives.

They are equipped with a smart keypad with dual LCD and LED displays.

The keypad is language selectable and offers users complete flexibility, providing programming and intelligent operator interface facilities.

In addition, the drives can be programmed on or offline using a PC.

"We think that the launch of MVW-01 drives is set to change the way engineers think about MV drives", said WEG Product Manager, Andrew Stevens.

"In the past, control engineers would veer away from MV drives because of their cost and complexity, and employ LV systems working at high currents".

"However the problem with using LV drives at high power, is that cable and installation costs are high".

"In addition, LV installations require shielded EMC cable, which is very expensive".

"MV drives, whilst usually costing more as a proprietary item, avoid these expenses, due largely to the lower current their cables carry, and the fact that they do not need to employ expensive EMC shielded cables".