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JD-BP Series Variable Frequency Drive

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 JD-BP Series High Voltage Inverter

The JD-BP series of medium voltage variable frequency drive, which is controlled by DSP, with the SVPWM and cell in series multi-level technology to guarantee the inverter to suit industrial fields. The harmonic content is much smaller than the standard of IEE519-1992. It has high power factor and good output wave quality without input filters, power factor compensation device and output filter. Motor heating caused by harmonics and Torque ripple, noise, dv/dt, and common mode voltage problems are also avoided. It fits for asynchronous and synchronous motors. 

Work Principle

Medium voltage variable frequency drive includes switch cabinet, phase-shifting transformer cabinet, power cell cabinet, control cabinet. Different industry scenes, the switch cabinet is different. Devices using high-high circuit structure, power cell in series to get the high voltage to drive the motor directly.

6kV series frequency inverter contains 5 cells each phase. 10kV series frequency inverter contains 8 cells each phase.

Medium voltage variable frequency drive of two-quadrant power cell includes rectifier diode, filter capacitor, IGBT components. The structure of power cell is H-bridge, the output is a group of SPWM wave.

Each phase has a number of power cells, using carrier phase-shifting technology, the cell’s output is added to form a multi-level voltage without the filter device, and the current harmonics are small and with little damage to cables and motors. 

When the motor is dragging, the energy flows to motor from grid through the rectifier circuit and inverter circuit, the frequency inverter works in the first and third quadrant. 

Four quadrants inverter can take energy back to power mains, the input rectifier diodes are replaced by IGBT compared with the two quadrants inverter. The power grid can provide energy to motor and receive energy generated by motor.

When motor is generating, the energy is taken back to power mains by controlling the amplitude and phase when bus voltage is larger than input voltage, at the moment inverter works in the second and fourth quadrant.

Performance and Feature

Vector control technology

Measure the AC motor stator current, divide it into excitation current and torque current according to
the magnetic field theory to achieve the purpose of controlling the AC motor torque.
The VFD using vector control technology has big start torque, fast dynamic response, high precision of speed adjustment, and can drive synchronous and asynchronous motors.

Oscillation suppression technology

When the motor is in light and no-load state, the current may fluctuate strongly, it may cause overcurrent or overvoltage then the protection is triggered. Using the current suppression algorithm, the phenomenon is avoided.

Master-slave control technology

The variable frequency drives can work in the master-slave state, they can communicate with each other by the data bus. When one works as the master, others work as the slaves, the master gives the frequency, torque data to the slaves according to their state.
The technology suits the belt conveyor and hoister.

Neutral point shift technology

When the cell is in fault, then it will be bypassed to ensure the three-source in balance within 100us using the neutral point moving technology.

Smart voltage regulation technology

The VFDs will regulate the output voltage in the setting value according to the bus voltage of the cell to reduce the effect of fluctuation of the mains.

The cell reset technology when running

When the cell is in fault, it will be bypassed when the VFD is running, no stop is needed.

No trouble power supply switching technology

variable frequency to industrial frequency: inverter adjust the output frequency to 50 Hz, then detect phase, frequency, amplitude of the industrial electricity and connect motor to industrial electricity at the right time. industrial frequency to variable frequency: inverter detect phase, frequency, amplitude of the industrial electricity, and connect motor to inverter from industrial electricity at the right time. The technology can be applied to more motor control and high-capacity motor soft start situation.