System Converter As A Complete Solution For The Medium Voltage Range

The new MVW3000 converter series from WEG for voltages from 2.3 kV to 8 kV and outputs from 280 kW to 2400 kW is implemented in multilevel technology with cascaded H-bridges (CHB). The multilevel topology is based on a series connection of three to ten 690 V low-voltage power units with an IGBT output inverter bridge in an H circuit, depending on the output voltage. According to WEG, this makes it possible to achieve cost-effective output voltage levels in the medium-voltage range using proven standard low-voltage components such as diodes, IGBTs and plastic film capacitors. What is special: The MVW3000 comes on the market as a control cabinet integrated complete system with medium-voltage isolating switch, fuses, multi-level feed transformer and frequency converter.

High network power factor

According to WEG, the MVW3000 system converter achieves a line power factor> 0.95 over the entire speed setting range without an additional harmonic filter or compensation capacitors. The overall device structure ensures excellent network perturbations with regard to harmonic harmonics in current and voltage THD I / V and TDD (according to IEEE-519, IEC61800-3, G5 / 4-1), according to the manufacturer. The converter efficiency, including the transformer, exceeds 95% over the entire speed setting range and reaches over 96% with a converter load of more than 40%. The precharge circuit for the multilevel mains transformer ensures that the transformer iron circuit is magnetized without starting current and for the precharging of the inverter DC link capacitors.

The interfaces between the converter CPU and the power section for IGBT control, temperature monitoring, voltage and current feedback, which are implemented in fiber optic technology, are intended to increase the immunity to interference and to effectively separate the control and power section. The power units (H-bridge) are designed with plastic film capacitors, semiconductor fuses and an automatic inverter bypass function. The almost sinusoidal output voltage / currents in the motors lead to a reduction in power loss, fewer vibrations and torque pulsations, according to WEG.

Motor protection devices integrated

In terms of increased reliability and system availability, the MVW3000 is equipped with motor protection devices to protect against overload, overheating and motor-rotor blockage. The power section and transformer temperature are also constantly monitored.

As a complete system, the MVW3000 simplifies installation and commissioning, WEG notes. The pull-out power units therefore guarantee easy maintenance and quick replacement. With a width of 3900 mm, height of 2210 mm and depth of 1100 mm, the system converter also has a compact footprint. In addition, the converter can optionally be equipped with all common industrial protocols such as Modbus, Profibus, Devicenet and Ethernet. (jv)