T-armature motor

The name comes from the resulting geometry of the metal, ferromagnetic body onto which the winding is applied. Due to this design, the T-armature motor has various disadvantages compared to a coreless motor. Because the T-armature motor can be manufactured relatively inexpensively, it is the most commonly used type in toy drives and other mass-produced micromotors.

The main technical disadvantages of a T-armature motor are:

• The achievable dynamics are limited due to the mass of the rotor and, thus, its inertia.
• Consequently, the T-shaped salient poles have magnetic preferred positions into which the rotor would "engage" if no further measures were taken. Even small cogging torques result in rough running of the rotor. One speaks of torque ripple here.
• Because the metal winding support turns in the magnetic field of the stator, electric voltages are induced in it that cause currents. These self-contained charge displacements, which are therefore known as eddy currents, produce current heat losses and heat the winding support. The energy that is converted to heat is thereby lost for torque formation. Winding supports are therefore produced from individual plates – the electrical conductivity is reduced in this way and the eddy currents limited in the axial direction.

In spite of the disadvantages, the T-armature motor is used increasingly in the industrial sector. Through modern materials, further developments and optimization, it has been possible to minimize many of the disadvantages. It is used above all with multi-pole motors and as direct drive, e.g., as brushless flat DC-motor with external rotor technology.

In applications in which the disadvantages of the T-armature motor are undesired, the bell-type armature motor is an option.