Main faults and solutions of VFD (Variable-frequency Drive)

1 Introduction

In recent years, with the development of power electronics technology, power semiconductor devices and frequency conversion control theory, VFD (Variable-frequency Drive) as an intelligent control power supply has been widely used in various industries. In the early 1990s, mainly imported brands such as Fuji , Mitsubishi, Siemens, ABB, etc. In the mid-1990s, Chinese-made VFDs (Variable-frequency Drives) gradually appeared on the market, mainly general-purpose VFDs (Variable-frequency Drives). At present, China's domestic VFD (Variable-frequency Drive) technology has gradually matured, and China's domestic VFD (Variable-frequency Drive) market share has gradually increased. As one of China's domestic VFD (Variable-frequency Drive) professional manufacturers, Chengdu Sunwoele Co. .,ltd., after just a few years of development, Sunwoele VFD (Variable-frequency Drive) is increasingly accepted by customers due to its superior performance. The VFD (Variable-frequency Drive) currently produced by Sunwoele mainly includes general-purpose HSF600/HFV series, Sunwoele pump1/Sunwoele pump2 series for fans and pumps, Sunwoele-zhusu/Sunwoele-zhusuzy series for injection molding machines and high-performance single-phase VFD (Variable-frequency Drive) Sunwoele1 series, other types of dedicated VFD (Variable-frequency Drive), and higher-performance vector VFD (Variable-frequency Drive) will also be introduced to the market one after another. This article mainly describes the common faults and treatment methods of Sunwoele VFD (Variable-frequency Drive) universal type in application, for the reference of users. the

2 General-purpose VFD (Variable-frequency Drive) main circuit

At present, China's domestic VFD (Variable-frequency Drive) is mainly low-voltage general-purpose VFD (Variable-frequency Drive). The VFD (Variable-frequency Drive) structure is divided into AC-AC VFD (Variable-frequency Drive) and AC-DC-AC VFD (Variable-frequency Drive), and the main voltage source type VFD (Variable-frequency Drive) is divided from the frequency conversion property Compared with the current source VFD (Variable-frequency Drive), the VFD (Variable-frequency Drive) currently produced in China is mainly based on the voltage source AC-DC-AC VFD (Variable-frequency Drive).

Its main circuit is mainly composed of rectifier circuit, filter circuit, inverter circuit and braking unit, among which IGBT (insulated gate bipolar transistor) constitutes the main hardware of VFD (Variable-frequency Drive), and the circuit functions of each part are briefly described as follows:

1 rectifier circuit

The three-phase bridge full-wave rectification circuit composed of VD1~VD6 rectifies the three-phase alternating current into direct current.

2 filter circuit

The DC voltage output by the rectifier circuit is a pulsating DC voltage, so the filter circuit is required to filter out the voltage ripple, and it also plays an energy storage role in the rectifier circuit and inverter circuit.

3 inverter circuit

The inverter circuit composed of switching tubes V1~V6 inverts the DC voltage into three-phase frequency and voltage-adjustable AC power to drive the three-phase motor, which is the key link for VFD (Variable-frequency Drive) to realize frequency conversion.

4 current limiting circuit

It is composed of a current limiting resistor R and a switch K. Since the terminal voltage of the filter capacitor is zero at the moment of power-on, the charging current of the capacitor at the moment of power-on is relatively large. Excessive current may damage the rectifier circuit. To protect the rectifier circuit in the VFD (Variable-frequency Drive ) The current-limiting resistor is connected in series to the DC circuit at the moment of power-on, and the resistor is short-circuited through the switch K after the capacitor is charged for a certain period of time.

5 braking circuit

It is composed of braking resistor RB and switch tube VB. Its main function is to consume the energy fed back by the motor and avoid damage to the VFD (Variable-frequency Drive) due to excessive pumping voltage.

Sunwoele’s general-purpose HSF600/HFV series VFD (Variable-frequency Drive) depends on the power level. The IGBTs used mainly include OPEC, Mitsubishi, Toshiba and other brands. The VFD (Variable-frequency Drive) power is below 18.5kW. The main circuit of the model is mainly composed of a seven-unit module integrating rectification, inverter, brake circuit and temperature detection. The model of 22kW and above is composed of a rectifier module and a three-way two-unit inverter module.

3Sunwoele VFD (Variable-frequency Drive) common faults and solutions

With the continuous promotion of the application, the Sunwoele brand is becoming more and more popular among users. In order to let users know more about Sunwoele VFD (Variable-frequency Drive) and make it easier for users to use, here are the faults that often occur in the use of SunwoeleVFD (Variable-frequency Drive) And the processing methods are as follows:

(1) Fault P.OFF

The Sunwoele VFD (Variable-frequency Drive) power-on display P.OFF will display 0 after a delay of 1~2s, indicating that the VFD (Variable-frequency Drive) is in the standby state. In the application, if the VFD (Variable-frequency Drive) keeps displaying P.OFF without jumping to 0 after power-on, the main reasons are that the input voltage is too low, the input power supply is out of phase, and the VFD (Variable-frequency Drive) voltage detection circuit is faulty. , When processing, first measure the three-phase input voltage of the power supply. The normal voltage of the R, S, and T terminals is three-phase 380V. If the input voltage is lower than 320V or the input power supply is out of phase, the external power supply failure should be ruled out. If the input power is normal, it can be judged that the VFD (Variable-frequency Drive) internal voltage detection circuit or phase loss protection is faulty. For Sunwoele HSF600/HFV series 90kW and above models VFD (Variable-frequency Drive), the main cause of the fault is internal phase loss The detection circuit is abnormal. The phase loss detection circuit is composed of two single-phase 380V/18.5V transformers and a rectifier circuit. Most of the faults are caused by detection of transformer faults. During processing, it is possible to measure whether the output voltage of the transformer is normal.

(2) Fault ER08

The ER08 fault code of the Sunwoele VFD (Variable-frequency Drive) indicates that the VFD (Variable-frequency Drive) is in an undervoltage fault state. The main reasons are that the input power is too low or lack of phase, the internal voltage detection circuit of VFD (Variable-frequency Drive) is abnormal, and the main circuit of VFD (Variable-frequency Drive) is abnormal. The general VFD (Variable-frequency Drive) voltage input range is 320V~460V. In practical applications, when the VFD (Variable-frequency Drive) is running at full load, under-voltage protection may occur when the input voltage is lower than 340V. At this time, the power grid should be increased The input voltage or VFD (Variable-frequency Drive) should be used with derating; if the input voltage is normal and the VFD (Variable-frequency Drive) has an ER08 fault during operation, it can be judged as an internal fault of the VFD (Variable-frequency Drive), as shown in Figure 1 Indicates that the KS contactor in the main circuit may be tripped, so that the current-limiting resistor is connected in series to the main circuit when the VFD (Variable-frequency Drive) is running. At this time, if the VFD (Variable-frequency Drive) is running with load, ER08 fault will occur At this time, it can be ruled out whether the contactor is damaged or the contactor control circuit is abnormal; if the main circuit of the VFD (Variable-frequency Drive) is normal, the cause of the ER08 alarm is mostly the fault of the voltage detection circuit. Generally, the VFD (Variable-frequency Drive) The voltage detection circuit is a group of outputs of the switching power supply, which is sent to the CPU processor after sampling and comparison circuits. When the set value is exceeded, the CPU outputs a fault blocking signal according to the comparison signal, blocks the IGBT, and displays the fault code at the same time.

(3) Fault ER02/ER05