WEG's new MVW-01 range is claimed to be setting new benchmarks for medium-voltage (MV) drive efficiency, achieving 99 per cent thanks to 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.
WEG says that the introduction of the MVW-01 drives means that it is the only supplier of speed variation systems for medium voltage 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 per cent of efficiency lost on 1MW drives, the user will pay an extra £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 multi-processor control architecture. They integrate a 32-bit high-performance processor (64-bit 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 complement 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, suitable for the operating conditions encountered in the most arduous industrial applications.
Compact, convenient and air-cooled
The MVW-01 drives deliver high levels of reliability and low noise levels (<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 ultra-reliable dry-type plastic film power capacitors. In addition, the design also includes withdrawable power arms for fast and simple maintenance.
Contradicting the widely held belief 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 off-line using a PC.
Andrew Stevens, WEG Product Manager, says: "We think that the launch of MVW-01 drives is set to change the way engineers think about MV drives. In the past, control engineers would veer away from MV drives because of their cost and complexity, and instead 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, while 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."