Closed loop control is a basic concept of cybernetics. It refers to a kind of control relationship in which the controlled output returns to the control input in a certain way and exerts control influence on the input. In cybernetics, closed-loop control usually refers to the feedback of output end to input through "side chain", so-called closed-loop control. The output feedback to the input and participate in the output re control, which is the purpose of closed-loop control, this purpose is achieved through feedback.

Braking resistor is a carrier used to consume regenerative energy of motor in the form of heat energy. It includes two important parameters: resistance value and power capacity. Generally, corrugated resistance and aluminum alloy resistance are widely used in engineering.

The frequency converter is widely used in petroleum, chemical industry, light industry, papermaking, rubber, electric power, metallurgy and many other industries. The speed regulation and energy saving of frequency converter improves the technological level and energy-saving resources for enterprise production.

With vector control inverter, the general meaning of motor control is: imitating the speed regulation characteristics of DC motor, the speed of three-phase asynchronous AC motor is adjusted by controlling its two vertical DC magnetic fields.

The daily maintenance and maintenance of frequency converter is the guarantee of safe work of frequency converter. If the daily maintenance and maintenance work is done well, the problems can be found and handled in time, which can make the inverter work in the best state for a long time, reduce the occurrence of shutdown faults and improve the efficiency of frequency converter.

The special feature of the converter of tower crane is that it is used to lift the potential energy load, with large impact and inertia. The starting torque and safety requirements of the converter are very high.

The influence of external fault on input side, such as bus voltage drop caused by external power grid fault, on the operation of high voltage inverter. A power plant unit in Guangdong Province once had such an accident: due to the transient fault of the external power grid

AC variable frequency speed regulation is a new technology developed in recent decades. It is recognized as one of the most promising speed regulation methods for its excellent speed regulation performance, remarkable power saving effect and wide applicability in various fields of national economy. AC variable frequency speed regulation technology is a comprehensive application of microcomputer technology

In the impact load such as electric welding machine, electric arc furnace, rolling mill and other occasions, the voltage often flickers; in a workshop, there are several frequency converters and other capacitive rectifier loads working, the harmonic generated by them has a very serious pollution to the quality of the power grid, also has a considerable damage to the equipment itself

When the frequency conversion / fan is used, the energy saving effect is the most obvious when the water pump is used in the industry. The energy-saving principle of other industries is roughly the same, which is achieved by lowering the motor speed when full speed operation is not required.

Frequency converter is a kind of power control equipment which uses frequency conversion technology and microelectronics technology to control AC motor by changing the frequency mode of motor power supply. Its use not only enables the motor to achieve more efficient operation, but also ensures the controllability of motor working conditions, which is very important in modern industry

3% impedance line reactor shall be used to reduce the power line transient voltage caused by capacitor switch, line notch, DC bus overvoltage trip and inverter over-current and overvoltage conditions. Line reactors improve the true input power factor and reduce crosstalk between drivers. The input line reactor provides some protection for the driver under short circuit conditions.

The theoretical life of this kind of electrolytic capacitor is more than 10 years. Many Japanese inverter can be used continuously for 10 years without any problem.

Capacitance in the circuit is generally represented by "C" plus a number (for example, C25 represents the capacitance numbered 25).

The rotation speed of induction AC motor (hereafter referred to as motor) is approximately determined by the number of poles and frequency of the motor. The number of poles of the motor is fixed according to the working principle of the motor. Since the pole value is not a continuous value (a multiple of 2, for example, the number of poles is 2, 4, 6), it is generally uncomfortable and the motor speed is adjusted by changing the value.

Induction motor, also known as "asynchronous motor", is a device that puts the rotor in the rotating magnetic field, under the action of the rotating magnetic field, obtains a rotational torque, so that the rotor rotates. The rotor is a rotatable conductor, usually in the form of a squirrel cage. It was invented by electrical engineer Nicholas Tesla in 1887. The article introduces the concept, inventor, working principle, basic structure, working mode, braking mode, asynchronous characteristics, specifications and fault inspection of induction motor.

When the induction motor is in the stop state, from the electromagnetic point of view, just like a transformer, the stator winding connected to the power supply is equivalent to the primary coil of the transformer, and the closed-circuit rotor winding is equivalent to the short-circuit secondary coil of the transformer; there is no electrical connection between the stator winding and the rotor winding

Frequency converter has been on the market for nearly 20 years in China. Because of its excellent performance and considerable power saving effect, it is widely used in all walks of life, and the utilization rate has reached about 30%. Especially in the past decade, it has developed rapidly, with an annual increase rate of more than 20%. Compared with other frequency converters

Due to the difference in performance and function between frequency converter and servo, their applications are not the same, so they are not allowed

Before the introduction of frequency converters, the bridge crane operator controlled the crane using contactor based controls. For low load cycle cranes, the system is equipped with single or double speed motors. For cranes with higher load cycles, they use so-called wound rotor motors.