Analysis Of The Phenomenon Of Misconduction Between The Upper And Lower Transistors Of The Same Bridge Arm In A Frequency Converter

In the single phase frequency converter power conversion link, each bridge arm consists of two switching devices, upper and lower. Under ideal control logic, these two devices switch alternately to synthesize the AC output waveform. However, when the upper and lower transistors of the same bridge arm are unexpectedly on simultaneously, a low-impedance path is formed between the DC bus, causing a large current surge to impact the converter's internal structure, resulting in severe shoot-through short circuits and unpredictable electromagnetic stress.

This mis-conduction event can be caused by timing mismatches in the drive signals, drift in drive chip parameters, or delays in control computation, leading to a mismatch in the dead-time arrangement during switching. The industry often combats this by designing meticulous dead-time logic and improving drive response accuracy. For example, some drive devices have built-in delay protection logic, increasing the time interval on the same bridge arm to prevent the upper and lower switches from triggering simultaneously.

In real-world engineering environments, mis-conduction not only affects the reliability of the frequency converter 50hz to 60hz three phase itself but also poses a potential impact on the connected load. The industrial frequency converter control unit needs to monitor the status of each bridge arm, using real-time sampling to determine abnormal switching states, helping maintenance personnel diagnose and locate potential driver or power device malfunctions.