The printed circuit board (PCB) motor consists of a rotor in the form a disc which is made up of non-magnetic and non-conducting material. Hence, the printed circuit board motor is also called as disc armature motor. The basic construction of a printed circuit board motor is shown in the figure.
The whole armature winding of the motor and the commutator are printed in copper on both sides of the rotor disc. The brushes are placed around the inner periphery of the rotor disc.
The disc armature of the motor is placed between two sets of permanent magnet poles which are mounted on ferromagnetic end plates. This entire configuration of the motor provides axial magnetic flux through the armature. The currents flowing radially through the rotor disc interacts with the axial flux to produce the torque that rotates the rotor.
The advantages of a printed circuit board motor are given as follows −
The printed circuit board motor can provide quick acceleration and retardation. Since it has a very low inertia and hence, its torque to inertia ratio is very high.
Since the rotor of the printed circuit board motor is made up of non-magnetic material, there is no cogging torque.
A printed circuit board motor has a high overload current capacity.
Since there is no iron in the rotor of the printed circuit board motor, the inductance of the armature is low.
The time constant of the armature is very small due to the low armature inductance of the printed circuit board motor.
In PCB motors, the armature current builds up very quickly and the full-load torque is developed almost instantly.
The lower inductance of the armature of the printed circuit board motor reduces the sparking and significantly increases the brush life.
The armature reaction and the flux distortion are negligible in a printed circuit board motor even at a high overload current. Hence, the speed-torque characteristics of a PCB motor is linear.
There are a large number of armature conductors, hence, the torque of a printed circuit board motor is smooth down to near-zero speed.
The characteristics and the high torque to inertia ratio of the printed circuit board motors make them suitable for the control applications. The PCB motors have a wide range of applications, some of them are given as follows −
PCB motors are used in high-speed tape readers
PCB motors are used in X-Y recorders
PCB motors are used in point to point tool positioners
PCB motors are used in robotics and other servo drives.
PCB motor with an in-built optical position encoder is used in place of the stepper motor.
The PCB motors are also suitable for some heavy-duty drives like lawn-mowers, heavy driven vehicles, etc.