SKEDSOFT
Transfer function of an armature controlled DC motor:
The armature-controlled DC motor uses the armature current ia as the control variable. The stator field can be established by a field coil and current or a permanent magnet. When a constant field current is established in a field coil, the motor torque is
When a permanent magnet is used, we have
where Km is a function of the permeability of the magnetic material.
The armature current is related to the input voltage applied to the armature by
where Vb(s) is the back electromotive-force voltage proportional to the motor speed. Therefore, we have
where ω(S) = sθ(s) is the transform of the angular speed and the armature current is
The load torque equation, we get,
Fig: 1 Block diagram of Armature-controlled DC motor
The relations for the armature-controlled DC motor are shown schematically in Figure 1. From the block diagram and let Td(s) = 0, we can solve to obtain the transfer function as
