Parallel magnetic fields feature uniform field lines that maintain constant spacing and direction throughout the field region.
Radial Magnetic Fields
In contrast, radial magnetic fields produce non-uniform fields where the magnetic field lines spread outward from the center, similar to spokes on a wheel.
Impact on Motor Torque
The torque (τ) produced in a DC motor is governed by the equation:
τ=nIAB⊥sinθ
Where:
n = number of turns in the coil
I = current through the coil
A = area of the coil
B⊥ = perpendicular component of magnetic field
θ = angle between area vector and magnetic field
Performance Comparison
Parallel Field Configuration
Torque varies significantly during rotation
Creates a rectified sinusoidal torque pattern
Maximum torque occurs only at specific angles
Torque reduces to zero at certain positions
Radial Field Configuration
Maintains more consistent torque throughout rotation
Field lines remain more perpendicular to coil area
Produces higher average torque
Results in smoother motor operation
Advantages of Radial Configuration
Radial magnetic fields are preferred in DC motors because they: