Q4Electrical Machines and Drives
Question
2 marks
Q.4. How does higher permeability of magnetic material of a D.C. machine affect its performance? [2]
Answer
Higher permeability magnetic material reduces the reluctance of the machine's magnetic circuit, meaning a given field MMF (ampere-turns) produces a larger air-gap flux, so the machine can develop its rated EMF and torque with a lower field current, reducing field copper loss. It also reduces the magnetizing current component drawn and improves the machine's efficiency and power factor (in AC machines), while also reducing the degree of magnetic saturation for a given operating flux density, keeping the machine's characteristics closer to linear over its working range.