When an induction motor is driven by an inverter, it injects common mode voltage into the motor. This voltage causes a common mode current to flow through the motor, inverter, and a system ground. The current may cause conducted EMI test failure of the drive. In an inverter driven motor controller, the sources of the common mode noise are AC/DC converter and DC/AC inverter. It is required to suppress both of them by common mode filters. These filters require energy storing elements such as inductors and capacitors.
USPTO Backgrounds
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