Feedback unit supplier reminds you that most ordinary frequency converters use diode rectifier bridges to convert AC power into DC, and then use IGBT inverter technology to convert DC power into AC power with adjustable voltage and frequency to control AC motors. This type of frequency converter can only operate in electric mode, so it is called a two quadrant frequency converter. Due to the use of a diode rectifier bridge in the two quadrant frequency converter, it is impossible to achieve bidirectional energy flow, so it is not possible to return the energy from the motor feedback system to the power grid. In some applications where electric motors need to feedback energy, such as elevators, hoists, centrifuge systems, and pumping units, it is only possible to add a resistance braking unit to the two quadrant frequency converter to consume the energy feedback from the electric motor. In addition, diode rectifier bridges can cause serious harmonic pollution to the power grid.
IGBT power modules can achieve bidirectional energy flow. If IGBT is used as a rectifier bridge, high-speed and high computing power DSP is used to generate SVPWM control pulses. On the one hand, it can adjust the input power factor, eliminate harmonic pollution to the power grid, and make the inverter truly a "green product". On the other hand, the energy generated by the feedback of the electric motor can be sent back to the power grid, achieving energy-saving effects.
For a motor alone, the so-called four quadrants refer to its mechanical characteristic curve that can operate in all four quadrants on the mathematical axis. The first quadrant is in a forward electric state, the second quadrant is in a feedback braking state, the third quadrant is in a reverse electric state, and the fourth quadrant is in a reverse braking state. A frequency converter that can operate the motor in four quadrants is called a four quadrant frequency converter. Simply put, a two quadrant ordinary frequency converter can only drive the motor to rotate forward or backward. Work in quadrants one and three. The kinetic energy generated when the electric motor idles can only be wasted. A four quadrant frequency converter (referring to the braking of an electric motor) can not only drive the motor in both forward and reverse directions, but also convert the kinetic energy of the motor when it idles into electrical energy and feed it back to the power grid. Make the electric motor operate in the generator state. More commonly used in situations of improvement.
The four quadrant frequency converter meets various industrial application requirements, especially suitable for high inertia potential energy loads such as lifting equipment. The equipment has a large rotational inertia GD and belongs to the repeated short-term continuous working system. The deceleration reduction from high speed to low speed is large, and the braking time is short, requiring strong braking effect or long-term heavy-duty electrical braking. In order to improve the energy-saving effect and reduce energy loss during the braking process, the deceleration energy is recovered and fed back to the power grid, achieving energy-saving and environmental protection effects.
The typical application of a four quadrant frequency converter is in situations with potential load characteristics, such as elevators, locomotive traction, oilfield kowtowing machines, centrifuges, etc. In some high-power applications, a four quadrant frequency converter is also required to reduce harmonic pollution to the power grid
The advantages of a four quadrant frequency converter
1. Compared to ordinary two quadrant frequency converters, it is more energy-efficient; The four quadrant frequency converter uses IGBT modules as rectification devices to achieve bidirectional energy flow. Without the need for any external devices, it can feed back the regenerated energy to the power grid, achieving energy-saving operation.
2. Reduce harmonic current on the grid side and achieve a power factor close to 1 at full load; Ordinary frequency converters, due to the use of diode rectification, generate a significant proportion of harmonic components, causing serious pollution to the power grid, interfering with the normal operation of other equipment, and even causing damage to other devices. The four quadrant vector frequency converter uses IGBT modules as rectification devices and generates PWM control pulses with high-speed and high computing power DSP, which can adjust the power factor and eliminate harmonic pollution to the power grid, making the frequency converter truly a "green product".