A bell-type armature motor is a highly dynamic DC-motor whose rotor is designed without an iron-based armature core. This construction was developed to overcome the typical technical disadvantages of a T-armature motor, such as increased inertia and cogging torque.
In a bell-type armature motor, the winding is self-supporting—meaning it is not wound on a carrier. The lack of mechanical stabilization by the carrier is compensated for by connecting the individual windings with a synthetic resin material. The self-supporting winding design is also known as an air-gap winding, bell armature winding, or coreless design.
The name bell-type armature motor is derived from the rotor’s appearance: the entire rotor—consisting of winding, commutator plate and commutator—resembles the shape of a bell.
In a bell-type armature motor, torque is transmitted from the winding to the shaft via the disc-shaped commutator plate, which is fastened to one side of the winding. The cylindrical commutator is mounted on the commutator plate. Because the rotor of a bell armature motor contains no iron core, no magnetic hysteresis losses occur during operation.
Since this rotor design does not use iron plates, the rotor inertia is very low compared to conventional DC motors. This enables high motor dynamics. At the same time, the coreless construction ensures cogging-free and exceptionally smooth running characteristics. As there are no magnetic hysteresis losses, a bell-type armature motor achieves very high levels of efficiency.
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