Motor Selection

General Motor Principles Motors convert electrical energy into mechanical energy using electromagnetic principles. 

The energy conversion method is fundamentally the same in all electric motors. 

• Magnetic Force:

 Magnetic poles generate invisible lines of magnetic force flowing from the North Pole to the South Pole as shown in This Figure . When magnetic poles of opposite polarity face each other, they generate an attractive force, while like poles generate a repulsive force.

• Left-Hand Rule:

Current in a conductor generates a magnetic field. Placing a conductor in the vicinity of a separate magnetic can generate a force that reaches its apex when the conductor is at 90° to the external field. The left-hand rule can help the user determine the direction of the force, as shown in this Figure

• Right-Hand Rule:

The movement of the conductor in the magnetic field induces an electromotive force known as the BEMF. The right-hand rule can determine the direction of the force as shown in this Figure. The Right-Hand Rule: Stretch out the right hand with the four fingers and the thumb on the same plane, the palm facing the north pole of the external magnetic field, and the thumb pointing in the direction of the velocity of v. The four fingers point in the direction of the induced electromotive force. The magnitude of the induced electromotive force can be calculated as: E BLv sin = θ

Where: E is the induced electromagnetic force (V). v is the velocity of the conductor (m/s). θ is the angular difference between B and L (rad).

When the motor rotates at an angular velocity of ω (rad/s) and there are N coil turns, the total electromotive force is: E 2BLvN 2BL rN K = = ω=ω Where: ω is the angular velocity (rad/s). r is the internal radius of the motor (m). KE=2rBLN is the electromotive force constant (V·s/rad).
Based on the parameters from This Figure: