To avoid the technical disadvantages of a T-armature motor, the bell-type armature motor was developed. Its winding is self-supporting, i.e., it is not wound on a carrier.
One therefore also speaks of a self-supporting winding, air-gap winding, bell-type armature winding or a coreless design. The lack of mechanical stabilization by the carrier is compensated for by a plastic element that connects the individual windings to one another. The transfer of torque from the winding to the shaft occurs by means of a disc – the commutator plate – which is fastened on one side in the winding. Attached to this commutator plate is the commutator, which likewise has a cylindrical shape. The entire rotor, consisting of winding, commutator plate and commutator, is reminiscent of a bell. The motor is therefore also referred to as a bell-type armature motor.
Because the otherwise typical iron plates are not present, the inertia of this type of rotor is very low in comparison to conventional rotors of DC motors. This enables high dynamics. With the coreless construction, the rotor thus also operates cogging-free and very quietly. As there are no magnetic hysteresis losses, the bell-type armature motor achieves very high levels of efficiency.
One disadvantage with this type of construction is to be taken into account, however: Without the coupling to a massive metal body, less heat can be stored in the motor. This reduces the overload capacity of bell-type armature motors and must be taken into account when selecting the optimum motor for the given application.
Recommendations
