Inverter parameters
Setting the parameters of a frequency converter is crucial during commissioning. Many first-time users of frequency converters are often overwhelmed by the sheer number and complexity of these parameters, which they may not fully understand. To address this, it's essential to grasp the fundamentals of frequency converter parameter setting: which parameters need to be set before trial operation; which parameters need adjustment during operation and their appropriate ranges; and how to prevent damage to the frequency converter due to improper parameter settings during commissioning.
Classification of frequency converter parameters
1. No need to adjust parameters; factory settings can be retained.
2. Parameters that need to be preset before trial operation
3. Parameters that need to be adjusted during trial operation
Commonly used inverter parameters include
1. Control method:
2. Minimum operating frequency:
3. Maximum operating frequency:
4. Carrier frequency:
5. Motor parameters:
6. Frequency hopping:
7. Acceleration and deceleration time
8. Torque Boost
9. Electronic thermal overload protection
10. Frequency Limitation
11. Bias Frequency
12. Frequency setting signal gain
13. Torque Limiting
How to set parameters for a frequency converter_Steps for setting parameters for a frequency converter
Inverter parameter settings (Part 1)
Inverters have many setting parameters, each with a certain selection range. During use, it is common to encounter situations where the inverter cannot work properly due to improper setting of individual parameters. Therefore, it is essential to set the relevant parameters correctly.
1. Control method: i.e., speed control, torque control, PID control, or other methods. After adopting a control method, static or dynamic identification is generally required based on the control accuracy.
2. Minimum operating frequency: This refers to the minimum speed at which the motor can operate. When a motor runs at low speeds, its heat dissipation performance is very poor. Prolonged operation at low speeds can lead to motor burnout. Furthermore, at low speeds, the current in the cables also increases, causing the cables to overheat.
3. Maximum operating frequency: The maximum frequency of a typical frequency converter is 60Hz, and some even reach 400Hz. High frequency will cause the motor to run at high speed. For ordinary motors, the bearings cannot run at speeds exceeding the rated speed for a long time. Can the motor rotor withstand such centrifugal force?
4. Carrier frequency: The higher the carrier frequency is set, the greater the higher harmonic components will be. This is closely related to factors such as cable length, motor heating, cable heating, and inverter heating.
5. Motor parameters: The inverter sets the motor's power, current, voltage, speed, and maximum frequency in its parameters. These parameters can be obtained directly from the motor nameplate.
6. Frequency hopping: Resonance may occur at a certain frequency point, especially when the entire device is relatively high; when controlling the compressor, the compressor surge point should be avoided.
Inverter parameter settings (Part 2)
Inverters have many function parameters, typically dozens or even hundreds, for users to select. In practical applications, it is unnecessary to set and adjust every single parameter; most of the time, the factory default values are sufficient.
I. Acceleration and deceleration time
Acceleration time is the time required for the output frequency to rise from 0 to the maximum frequency, while deceleration time is the time required for the frequency to drop from the maximum frequency to 0. Acceleration and deceleration times are typically determined by the rise and fall of the frequency setting signal. When the motor accelerates, the rise rate of the frequency setting must be limited to prevent overcurrent, and when decelerating, the fall rate must be limited to prevent overvoltage.
Acceleration time setting requirements: The acceleration current should be limited below the inverter's overcurrent capacity to prevent overcurrent stall and inverter tripping. The key point for deceleration time setting is to prevent excessive voltage in the smoothing circuit to avoid regenerative overvoltage stall and inverter tripping. Acceleration and deceleration times can be calculated based on the load, but during commissioning, it is common practice to initially set a longer acceleration/deceleration time based on the load and experience, observing for overcurrent and overvoltage alarms by starting and stopping the motor. Then, the acceleration/deceleration time is gradually shortened, ensuring no alarms occur during operation. Repeating this process several times will determine the optimal acceleration/deceleration time.
II. Torque Boost
Also known as torque compensation, it's a method to increase the f/V ratio in the low-frequency range to compensate for the torque reduction at low speeds caused by the resistance of the motor stator windings. When set to automatic, it automatically increases the voltage during acceleration to compensate for the starting torque, allowing the motor to accelerate smoothly. When using manual compensation, the optimal curve can be selected through testing based on the load characteristics, especially the starting characteristics. For variable torque loads, improper selection can lead to excessively high output voltage at low speeds, wasting electrical energy, and may even result in high starting current and insufficient speed during motor start-up under load.
