Siemens MM4 series VFD (Variable-frequency Drive) maintenance example

0 Preface

The AC speed control system composed of VFD (Variable-frequency Drive) and AC motor has excellent speed control performance, but as its application range continues to expand, it will also cause failures due to various reasons during work. The MM4 series general-purpose VFD (Variable-frequency Drive) is affected by various factors when running on site, so the causes of failure vary widely. The same failure phenomenon may be caused by different reasons, and the same failure cause may also cause different Fault phenomena, some fault causes are obvious, while some fault causes are very hidden. Therefore, on-site experience is valuable. You can rely on the complete protection functions of VFD (Variable-frequency Drive) and accumulate on-site experience to improve VFD (Variable-frequency Drive) fault handling capabilities to shorten VFD (Variable-frequency Drive) fault shutdowns. time.

1 Characteristics of Siemens MM4 series general-purpose VFD (Variable-frequency Drive)

MM4 series general-purpose VFD (Variable-frequency Drive) includes: MM410 compact general-purpose VFD (Variable-frequency Drive), MM420 basic general-purpose VFD (Variable-frequency Drive), MM430 energy-saving general-purpose VFD (Variable-frequency Drive) and MM440 vector Type general VFD (Variable-frequency Drive) and other 4 series. MM440 vector general-purpose VFD (Variable-frequency Drive) is a widely used multi-functional standard VFD (Variable-frequency Drive) without speed sensor flux current vector control method. It has low-speed and high-torque output, good dynamic characteristics and Features include strong overload capability. MM430 energy-saving general-purpose VFD (Variable-frequency Drive) is a dedicated VFD (Variable-frequency Drive) for fans and pumps. MM420 basic universal VFD (Variable-frequency Drive) is a modular standard VFD (Variable-frequency Drive), which is suitable for most general-purpose motor frequency conversion speed control applications. It has complete control functions. MM410 compact universal VFD (Variable-frequency Drive) has the characteristics of low power, compact structure, small size, flexible and convenient use, and simple installation.

2 Examples of common fault repairs

1) Fault phenomenon: There is an MM410 VFD (Variable-frequency Drive), and the panel displays the fault code [F231] or [F002] after powering on.

Cause analysis: There are generally two possible causes of this failure. The common cause is a problem with the power drive board, and a small number of it is caused by the main control board.

Solution: You can try changing a main control board first, otherwise the problem must be in the power driver board.

2) Fault phenomenon: There is an MM410 VFD (Variable-frequency Drive). After powering on, there is no display on the panel. The indicator light under the panel indicates that the green light is off and the yellow light is flashing quickly.

Cause analysis: This phenomenon shows that the circuits of the rectifier and switching power supply are working basically normally. The problem lies in a certain circuit of the switching power supply that is abnormal, such as breakdown or open circuit of the rectifier diode. You can use a multimeter to measure several rectifier diodes of the switching power supply. Easy to spot problems. This problem is generally caused by the low withstand voltage of the diode and the impact of power supply pulsation.

Solution: The problem is solved by replacing the corresponding rectifier diode.

3) Fault phenomenon: There is an MM420-3kW VFD (Variable-frequency Drive). The fault code [F0022, F0001, A0501] is displayed indefinitely. When the case is knocked or the panel and mainboard are moved, the display is normal.

Cause analysis: Generally, it is a connector problem. Checking the connectors in various parts can solve the problem. It was also found that some machines were caused by quality problems or poor welding of the RC components on the circuit board.

4) Fault phenomenon: There is a MM430-55kW VFD (Variable-frequency Drive), and [-----] is displayed after powering on.

Cause analysis: This failure is caused by a problem with the main control board. The user did not strictly follow EMC regulations during the installation process and did not route strong and weak currents separately. Due to strong current interference in the peripheral control circuits, some components of the main control board (such as chip capacitors, resistors, etc.) were damaged and the grounding was poor; Or the shielded wire is not used, causing the I/O port of the main control board to be burned. But sometimes it has something to do with the poor heat dissipation of the main control board, and there are also some problems that occur on the power board.

Solution: In most cases, the problem can be solved by replacing the main control board.

5) Fault phenomenon: An MM440-200kW VFD (Variable-frequency Drive) has a large load inertia and a large starting torque. When the equipment is started, the frequency can only rise to about 5 Hz and then cannot go up again, and an alarm is issued. The fault code [F0001] is displayed, indicating VFD (Variable-frequency Drive) overcurrent.

Reason analysis: As a VFD (Variable-frequency Drive) itself, there is no problem. The problem is that the customer parameters are set improperly and the control method is adopted.