Medium Voltage Variable Frequency Drive
The MV Drives are available from 3.3KV to 11 KV and rating from 150KW to 100,000 KW.MV VFD is complied with IEEE 519-1992 and GB/T14549-1993. They do not require the additional input filter, saving the cost for harmonic elimination. Because of the high power factor of the system, the compensation device for power factor is not needed, thus the reactive power are effectively reduced, saving the cost for the grid capacity enlargement.
MV VFD adopts AC-DC-AC mode, the electronic switch component is IGBT. It is highly reliable by means of the power cells connected in series and voltage overlapping method.MV VFD has a number of power cells connected in series, the independent phase-shift power is supplied to each power cell by the isolated transformer. Changing the power cells number in each phase you can get different output voltage conveniently without the limitation for the components’ withstand voltage.
Medium Voltage VFD is divided into two types:
1. General VFD.
The General VFD realizes energy-saving by adjusting the motor’s rotator speed, and is mainly used for fans and pumps in Power, Mining, Petrol-chemical, Metallurgy, Cement, Municipal industries, etc.
2. High-performance VFD.
The High-performance VFD, with the use of the vector control and regenerative technology, this results in a constant torque, quickly dynamic response, higher precision, a wider scope of speed regulation and faster braking, etc. It can transfer the regenerative energy into the grid during the load is braking, which is mainly used for mining hoist, conveyor, rolling mills, marine and engine, etc.
Isolated Transformer: The multi-windings at the secondary side can provide independent phase-shift power suppy for the power cells. It can efficiently reduce harmonic distortion and improve the current waveform of the grid system.
Cooling Fan of Transformer: The proper cooling fan is configurable for the dry type transformer depending on the power ratings.
Power Cell Cabinet
Controller: The voltage vector PWM control, signals measurement and controlling with complete electric isolation by the optic fiber communication between controller and power cells.
Power Cell: The modular designs, easy to production, maintenance and replacement with each other.
I/O Board: The interface of digital and analog signals, adaptable for the various applications on site.
HMI: LCD display in multiple-language, easy to operation, parameter setting, status display, fault recording, etc.
Manual / Automatic Bypass Cabinet (Optional)
To ensure the continuous production in case that the VFD is fault or stopped, the bypass cabinet allows the motor to be driven by the grid system.
It has the following advantages:
No need for the additional output filter.
Directly driving general synchronous or asynchronous motor
No de-rating operation on the motor
No dV/dt stress on the insulation of motor and cables
No torque ripple, extending service life of motors and mechanism
No cable length restriction within the acceptable voltage drop.
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