Medium voltage variable frequency drive
● Power Generation: Induced draft fan, forced draft fan, condensate pump, feed pump, primary air fan, secondary air fan, booster fan, circulating pump, mill fan, slurry pump etc.
● Cement: draft fan, high-temperature fan, air blower, dust collection fan, grinding machine etc.
● Metallurgy: blast furnace blower, slurry pump, feed water pump, dust fan, compressor etc.
● Petroleum Chemical: Water injection pump, crude oil pump, Compressor, fan, circulation pump, etc.
● Urban water supply: Water delivery pump, water intake pump, water supply pump, sewage treatment industry, self-fractionating pump etc.
● Minerals & Mining: Mud pump, ventilation fan, belt conveyor, slurry pump etc.
● others: Loads such as fan, pump and compressor in pharmaceutical, paper making and wind tunnel test.
WLD-HVF series medium voltage inverter adopts Power Units in series and overlapping technology to obtain MV directly by means of overlap wave. Low voltage power unit is an actually improved motor variable frequency inverter, which takes full advantage of mature technology. WLD-HVF belongs to High-high voltage source inverter, the customer can connect high voltage (3/6/10KV) directly to WLD-HVF, then WLD-HVF output high voltage (3/6/10KV) correspondingly. WLD-HVF consists of phase-shifting transformer, power unit cabinet and controller, for example:
6KV Series: Consisting of 15 AC power units with 690V. Every 5 power units are connected in series to form one phase (phase voltage 3450V), 3-phase Y-type connection, so the Line voltage can reach to 6KV.
Voltage Overlap Diagram
From the above, different voltage output, the quantity of power units is different, but the working theory is exactly identical. All power units receive the indicator from same central process controller. There is a phase difference in secondary windings of transformer which provide energy for power unit, in this way, most of the harmonics current caused by independent power unit will be eliminated, so the primary winding current is approximately sine wave, the harmonics current flowing into power grid are so few, even under the rated load, the harmonics contents is lower of 3%.
The power unit is AC-DC-AC structure, equivalent to a low-voltage power source inverter of 3-phase input single-phase output. The rectifier side is diode three-phase full bridge circuit and the IGBT inverter bridge can be controlled through sine PWM mode to output single-phase AC. All power units are fully identical in structure and electrical performance, very easy for maintenance and replacement.
Structural Diagram of Power Unit
● Voltage source High-high frequency inverter, it can realize No-step speed regulation, which makes the typical motors into intelligent motors.
● Low harmonics input and high power factor, the typical value for power factor is 0.95 through whole speed regulation, even higher, no need for power factor compensation.
● WLD-HVF output few harmonics; the motor does not generate extra heat and noise.
● Modularized design of power units, interchangeable and easy to produce and repair, the equipment can find any fault exactly based on advanced diagnostic procedures in MPU.
● The inverter still can operate even the faults for part of power units exists, if there are faults happen for inverter, the system can switch to power frequency through bypass function.
● Applicable to all kinds of power grid at home and abroad and suitable for typical high voltage motor.
● Colorful touch screen, easy to operate and maintenance.
● Able to realize remote control, DCS operation and communications with Host, and support all kinds of communications interfaces such as CAN, Profibus, Modbus, RS232, RS485 etc.
● Applied latest components, master control chip adopted TI’s DSP F28335 and ALTERA’s FPGA of EP3C to realize powerful processing capacity; Sampling adopted AD’s AD7606 with 16 bit to ensure control accuracy of the system.
● the switchgear can satisfy safety requirements, and the pressure-relief channel of high voltage switch can ensure safe use of operators.