Content Overview
The frequency converter is an electrical device. For safe operation, ensure that the frequency converter is powered off, and wait for more than 5 minutes after disconnection. Additionally, the input power lines R, S, T and output lines U, V, W must be removed before proceeding!
▲ Frequency Converter Main Circuit Diagram
Module Testing
First, disconnect the input lines R, S, T and output lines U, V, W of the frequency converter, then check whether the rectifier module and inverter module are functioning normally.
▲ Power Wiring Schematic
First, set the multimeter to the “diode” mode, then use the following steps to test:
Rectifier Module TestingConnect the black probe to the positive terminal P(+), and the red probe to R, S, T in sequence, recording the values displayed on the multimeter; then connect the red probe to N(-), and the black probe to R, S, T in sequence, recording the multimeter’s display values. If the six display values are roughly balanced, it indicates that the diode rectifier or soft start resistor is functioning correctly; otherwise, the corresponding rectifier module or soft start resistor is damaged.Failure Phenomenon: No Display.Inverter Module Testing
Connect the red probe to the negative terminal P(+), and the black probe to U, V, W in sequence, recording the values displayed on the multimeter; then connect the black probe to N(-) and the red probe to U, V, W in sequence, recording the multimeter’s display values. If the six display values are roughly balanced, it indicates that the IGBT inverter module is functioning correctly; otherwise, the corresponding IGBT inverter module is damaged.Failure Phenomenon: No Output or Fault Reported..
▲ Power Connection and Control Interface
Dynamic Testing
1. Preparation for Power-On TestingOnly after the static test results are normal can dynamic testing be performed, i.e., powering on the machine. Before and after powering on, the following points must be noted: Before powering on, confirm that the input voltage is correct; connecting a 380V power supply to a frequency converter designed for 220V will cause damage (to capacitors, varistors, modules, etc.).Check whether the terminals of the frequency converter are correctly connected and secure; loose or abnormal connections can sometimes cause faults, and in serious cases, may lead to equipment damage.2. Power-On InspectionAfter powering on, check the fault display content and initially determine the fault and its cause. If no faults are displayed, first check for abnormal parameters and reset them before starting the frequency converter under no load (without connecting a motor) and testing the U, V, W three-phase output voltage. If there are issues like phase loss or three-phase imbalance, then the module or driver board may be faulty. 3. Load Testing
Conduct load testing when the output voltage is normal (no phase loss, three-phase balanced). It is best to perform full load testing.
1) Use the frequency converter to drive a matched asynchronous motor under no load, adjusting the frequency f from 50Hz down to the lowest frequency;
2) During this process, use an ammeter to check the no-load current of the motor. If the no-load current remains stable and relatively unchanged during the frequency decrease, then it indicates a good frequency converter;
3) The lowest frequency can be calculated as follows: (synchronous speed – rated speed) × pole pairs p ÷ 60. For example, for a 4-pole motor with a rated speed of 1470 RPM, the lowest frequency = (1500 – 1470) × 2 ÷ 60 = 1Hz;
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