When the frequency converter drives the three phase asynchronous electric motor, parameter setting is the core link to ensure the efficient and stable operation of the system. Reasonable parameter setting should be based on the motor characteristics, load type and control requirements. The following is a classification and analysis of the key points of parameter setting:
I. Basic Parameters of the Motor (Core Foundation
The frequency converter must accurately identify the parameters on the motor nameplate; otherwise, it may lead to overcurrent, overload or control failure.
• Rated power (Pn) : Consistent with the motor nameplate, it affects the capacity selection of the frequency converter and the overload protection threshold.
• Rated voltage (Un) : It is usually the line voltage (such as 380V). Some frequency converters support phase voltage setting, which needs to match the motor input requirements.
• Rated current (In) : Key protection parameter! The overcurrent protection (OC) of the frequency converter is based on this (generally set at 1.5 times In as the limit).
• Rated frequency (Fn) : Generally 50Hz (or 60Hz). If the motor is designed for a non-standard frequency (such as 100Hz), it needs to be adjusted synchronously.
• Rated speed (Nn) : It is used to calculate the slip rate. In vector control mode, this parameter is required to optimize the torque output.
• Number of poles: It assists in determining the synchronous speed of the motor (n=60f/p) and affects the low-frequency torque characteristics.
Ii. Control Mode and Given Mode (Determining the Operation Logic)
Select the control mode based on the load characteristics. Common modes are as follows:
• V/F Control (General Scenarios) :
• V/F curve: For constant torque loads (such as conveyor belts), select "Linear Curve"; For fans/pumps (variable torque), select "square curve" (to reduce low-frequency loss).
• Torque boost (low-frequency compensation) : Increase the voltage at low frequencies (such as <10Hz) to compensate for the stator resistance voltage drop and prevent locked rotor. It needs to be adjusted step by step (generally 5% to 15%). If it is too high, overcurrent is likely to occur.
• Vector Control (High-precision scenarios) :
• Control mode: Sensorless vector control (SVC) or closed-loop with encoder (VC). VC needs to set the encoder type (such as incremental/absolute value) and parameters.
• Motor self-learning: "static self-learning" (obtaining stator resistance, leakage inductance, etc.) must be carried out; High-precision scenarios require "dynamic self-learning" (simulating load operation and identifying rotor parameters).
• Given pattern:
• Panel setting (local operation), terminal setting (external potentiometer/switch), communication setting (Modbus/CAN, etc.). The function of the corresponding input terminal needs to be set (for example, AI1 is given from 0 to 10V).
Iii. Protection Parameters (Key to Safe Operation
• Overcurrent protection (OC) : Generally set at 1.5 to 2 times the rated current of the motor, with a response time (e.g., 60 seconds). It can be more sensitive under vector control.
• Overload protection (OL) : For motor overheating, the thermal capacity of the motor needs to be matched. For example: 60 seconds at 1.1 times In and 30 seconds at 1.2 times In (inverse-time characteristic).
• Overvoltage protection (OU) : DC bus voltage threshold (such as 700V, corresponding to an input voltage of 380V), which needs to be combined with deceleration time or braking resistor (a must for large inertia loads).
• Under-voltage protection (LU) : When the bus voltage is too low (such as 320V), it prevents motor loss of control due to power fluctuations.
• Phase loss protection: Detects input/output phase loss to prevent the motor from overheating due to asymmetric operation.
Iv. Acceleration/Deceleration and Start-Stop Parameters (Affecting Dynamic Performance)
• Acceleration time (t1) : The time it takes for the frequency to rise from 0 to the maximum frequency. For heavy-load starts (such as hoists), an extension (such as 30 seconds) is required to avoid overcurrent. Light load can be shortened (such as 5 seconds).
• Deceleration time (t2) : The time it takes for the frequency to drop from its maximum to 0. For large inertial loads (such as centrifuges), an extension (e.g. 40 seconds) is required, or a braking resistor/feedback unit should be configured to prevent overvoltage.
• Start frequency (f_start) : Initial start frequency (such as 0.5Hz), combined with torque boost to avoid low-frequency stalling. Some loads (such as conveyor belts) need to be set to start directly at 5Hz or above.
• Stop mode: Free stop (inertial stop) or soft stop (deceleration to 0), the latter requires setting a deceleration time.
• Point motion control: Point motion frequency (such as 5Hz), point motion acceleration time (such as 2s), used for debugging or short-distance movement.
V. Advanced Functional Parameters (Optimizing Operational Efficiency)
• PID control (closed-loop scenario) :
Set the feedback signal type (4-20mA/0-10V) and target value (such as constant voltage 5bar).
Adjust the proportional (P), integral (I), and differential (D) parameters to avoid overshoot or response lag (e.g., P=10, I=2s).
• Carrier frequency: Affects motor noise and inverter efficiency. High carriers (such as 16kHz) have low noise but generate a lot of heat from the frequency converter. Low carriers (such as 4kHz) are suitable for noise-sensitive scenarios (such as medical equipment).
• Energy-saving mode: For fan/pump loads, "Automatic Energy saving" can be enabled, and the frequency converter adjusts the output voltage according to the load (reducing iron loss).
• Multi-speed control: Set the frequency of each speed segment (such as 10Hz, 30Hz, 50Hz) and the switching time, for periodic working conditions (such as assembly lines).
Vi. Precautions
• Motor and frequency converter matching: Priority should be given to using dedicated frequency conversion motors (F-class insulation, low harmonic loss), while ordinary motors need to be derated (such as reducing the rated current by 10%).
• Cable length: For long cables (>50m), an output reactor should be added to suppress the insulation aging of the motor caused by harmonic reflection.
• Ambient temperature: The operating temperature range of the frequency converter is generally -10 to 40℃. In high-temperature environments, derating is required (for example, reducing the output current by 20% at 40℃).
• Grounding and shielding: Reliable grounding (grounding resistance <10Ω), separate wiring for power lines and signal lines to reduce electromagnetic interference.
Summary: Parameter Settings should revolve around "motor characteristics - load requirements - control objectives". The core lies in accurately inputting motor parameters, selecting matching control methods, and optimizing operational stability through protection and dynamic parameter optimization. During debugging, verification can be carried out step by step (such as setting basic parameters first, then adjusting acceleration and deceleration times, and finally optimizing advanced functions) to avoid the difficulty of troubleshooting caused by modifying multiple parameters at once.
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