I. Basic knowledge of frequency converter

 Frequency converter is a power control device, which can control the speed of the motor by changing the frequency of the power supply.Frequency converter is composed of rectifier, filter, inverter and other parts, which can realize the soft start, energy saving control, accurate speed regulation and so on.

 II. Basic connection and installation of frequency converter

 1. Power access: the power input terminal of the frequency converter should be connected to the three-phase four-wire power supply, and ensure that the voltage and frequency of the power supply are in accordance with the rated value of the frequency converter.

 2. Motor access: the cable of the motor should be connected to the output terminal of the frequency converter, and pay attention to the cable of the motor should meet the rated current and voltage requirements of the frequency converter.

 3. Grounding: the frequency converter should be connected to a reliable ground wire to ensure electrical safety.

 III. Main function code of frequency converter

 The main function code of the frequency converter is used to set and adjust the parameters of the frequency converter.The function code of each frequency converter may be different, and it needs to be set according to the specific manual of the frequency converter.Some common function codes include: frequency setting, operation mode selection, start and stop parameters, PID control parameters, etc.

 IV. Operation mode selection of frequency converter

 The operation mode of the frequency converter determines the operation mode and characteristics of the motor.Common operation modes are: 1. Linear mode: the motor accelerates or decelerates in a linear way, which is suitable for most applications.

 2. Parabolic mode: the motor accelerates or decelerates in a parabolic way, which is suitable for the case where the set speed needs to be reached quickly.

 3. Extended mode: the complex acceleration and deceleration curve is realized by setting multiple running segments, which is suitable for the occasion where the motor speed needs to be accurately controlled.

 V. Setting of frequency parameters of frequency converter

 Frequency parameters are key parameters for controlling the speed of the motor.They need to be set according to the actual demand:

 1. Basic frequency: the basic speed of the motor, which can be set according to the actual demand.

 2. Maximum frequency: the maximum speed allowed by the motor, which should not exceed the rated speed of the motor.

 3. Minimum frequency: the minimum speed allowed by the motor, which should not be lower than the rated speed of the motor.

 VI. Start and stop parameters of frequency converter

 Start and stop parameters of frequency converter are used to control the start and stop process of the motor:

 1. Start frequency: when the motor starts, the frequency output by the frequency converter rises from 0 to the set value.

 2. Stop frequency: when the motor stops, the frequency output by the frequency converter drops from the current value to 0.

 3. Acceleration and deceleration time: the time required by the motor from the start frequency to the maximum frequency and from the maximum frequency to the stop frequency. These parameters need to be reasonably set according to the actual application to ensure the smooth start and stop of the motor.

VII. PID control parameters of  the  frequency converter

 PID control is a commonly used control algorithm for the closed-loop control of the system.PID controller calculates the proportion, integral and differential errors by comparing the error between the set value and the actual value, and outputs control signals to reduce the error.In the inverter, PID controller is used to adjust the speed of the motor and the pressure of the system and other parameters.The following are general suggestions for setting PID control parameters:

1. P (proportional coefficient): used to adjust the response speed and deviation size of the system.It can be adjusted according to the response speed and deviation size of the system, and the value range is usually 0.1-1.0.

 2. I (integral coefficient): used to eliminate the steady-state error of the system.It should be adjusted according to the steady-state error size of the system, and the value range is usually 0.01-0.1.If the integral coefficient is set too large, it will lead to oscillation or overshoot of the system;if the integral coefficient is set too small, the steady-state error of the system is difficult to eliminate.

 3. D (differential coefficient): used to improve the dynamic performance of the system.It should be adjusted according to the dynamic performance of the system, and the value range is usually 0.001-0.01.If the differential coefficient is set too large, it will lead to increased sensitivity of the system to noise; If the differential coefficient is set too small, the dynamic performance of the system is not obviously improved. Sampling time: used to determine the sampling interval of the PID controller.

The sampling time should be adjusted according to the response speed and stability requirements of the system, and the value range is usually 0.1-1.0 seconds.Sampling time is too long will lead to slow response of the system;sampling time is too short may lead to instability of the system.When adjusting the PID parameters, the other two coefficients can be fixed first, and only one of them can be adjusted to observe the response and steady-state error changes of the system, and gradually adjust until satisfactory performance indicators are achieved.At the same time, the performance changes of the system under different working conditions should be paid attention to, and the PID parameters should be adjusted in time to meet the actual needs.