Proposing the New Layered-Shield Structure for Shaft Voltage Reduction in IPMSM

As the era of electrification advances, the demand for increased power density and high efficiency in electric motors, such as those in electric vehicles (EVs) and e-mobility, has been rising. This has led to an increase in the application of higher dc voltages and the use of high-performance switching devices. In particular, with the design of high-performance interior permanent magnet synchronous motors (IPMSMs), which are widely used as traction motors in many vehicles, there is a growing need to address motor faults. IPMSMs are driven by PWM inverters for traction motors, and during this process, a common-mode voltage (CMV) occurs, where the sum of the three-phase voltages of the winding does not become zero. This CMV component causes circulating currents through the parasitic capacitances within the motor from the windings, generating current paths. As a result, voltage is induced on the motor shaft, which applies voltage to the bearings, leading to bearing damage. Such bearing faults can cause mechanical and electrical defects in the motor and even lead to vehicle breakdowns. Therefore, since bearing faults can threaten the driver’s life, this article proposes a new shield structure designed to reduce shaft voltage and prevent bearing faults.