Cold water machine the compressor for constant torque load, the compressor refrigeration capacity and its speed is proportional to the consumed power, from the perspective of cycle analysis.
By using the method of changing speed adjust energy has good part load operation efficiency, compressor drive machine is an induction motor, induction motor to change speed although there are many kinds of methods, but used to drag the compressor, from the speed of the motor torque characteristics, appropriate method is to use frequency control of motor speed.
the refrigeration unit with variable frequency energy is, speed adjustment is cold, and the advantages of high precision temperature control and easy to realize automatic control, the frequency control of motor speed as a kind of effective energy saving control means, in many general machinery products, including refrigeration compressor, the transfiguration of widely used in the control.
compression with frequency converter to change the cold water machine the frequency of the motor power supply.
The power of the motor voltage with flat rate is proportional to the change.
So it is also called variable voltage variable frequency VVF, frequency converter is the pain of power semiconductor device faulting the power frequency power conversion to another frequency power control device, now use the frequency converter mainly adopts has been in a way, the power frequency ac power first through the rectifier converts dc power supply, and then to convert the dc power supply frequency.
Voltage can be controlled ac power supply motor.
Frequency conversion circuit generally by the rectification of the intermediate links, inverter and control of four parts, the rectifier part is divided into three bridge uncontrolled rectifier and inverter part for IGBT three-phase bridge type inverter, and the output of PWM waveform.
Intermediate dc link for filtering.
Dc energy storage and buffer reactive power.