Fault Diagnosis Of Brushless DC Motor Drives

Motor, as the mechanical and electrical energy conversion device, its application has been in almost every field of national economy and people’s daily life. Brushless DC motors which use full-control power switch parts controller is replacing the old type dc motor. But because of its vulnerability and the intricacy of control, the driving machine is the most fragile part in the whole system, especially the inverter for all PWM control. So the key for safety and stable operation of brushless dc motor is avoiding the inverter faults effectively.Using the current signal to diagnose inverter faults information is apt to be affected by the load, noise and other factors, and easily appears incorrectly diagnosed with light-load or no-load. Focused on this issue, the logical analysis method on leg neutral-point voltage and pulse signal is purposed to realize the diagnosis of the open circuit faults of inverter switches, and the logical expressions of fault output signals under condition of inverter power tube open-circuit faults and interrelated hardware circuit design is also elaborated. This is by transformed the collected voltage signal into logic electric level and calculated by NAND of the logic gate to diagnose the specific switch fault. Delaying the rising edge of inverter power tube’s pulse signal can effectively avoid the error diagnosis caused by the power tube’s switching on/off. Simulation analysis and experiment results show that this method can effectively overcome the influence of the noise, and it is independent of the load. The hardware circuit with low cost is very suitable for both open loop and closed loop system. Beside, the diagnosis time can be limited within one cycle.