The inverter circuit of dc brushless motor (DCBLM) needs feedback diodes to protect the switching element from counterelectromotive force.
In this paper, we describe the computational method of magnetic field analysis of DCBLM with feedback diodes. The electric circuit equations were formulated based on the theoretical formula of the PN-junction diode. And, solving these equations with the magnetic circuit equation by using the FEM, the electrical characteristic and the magnetic property of DCBLM were calculated. By replacing the switching elements with variable resistor, and transforming electric circuit by using Ho•Thevenin's theorem, the route of current is not necessary to change according to the state of feedback diode and switching elements.
This method for feedback diodes is confirmed by the analysis of the permanent magnet DCBLM.