Practical application of slotless armature winding

In the development of large steam turbine generators, especially the emergence of superconducting machines, and in DC motors and control motors, slotless motors have emerged.


Turbine generator with air gap winding

As the capacity of the power system increases, the growth of the transmission line, and the increase of the single unit capacity of the generator, in order to improve the stability of the system, the turbine generator is required to have a large air gap to satisfy the short circuit ratio. Large steam turbine generators have an air gap of more than 100 mm. Therefore, it is considered to eliminate the stator slots and place the stator windings in the air gap to form a slotless or air gap winding.


Like a slotless DC motor, the armature core is a slotless cylindrical iron yoke. The slotless winding includes a large insulating barrel near the inner surface of the yoke, which is insulated from the ground, with the windings distributed on the inside and cooled by internal cooling.


For slotted double-layer windings, each coil side must be grounded to the rated voltage of the motor, thus making the slot utilization very low, especially for large high-pressure turbine generators. The inner copper wire has the same cross section, so the groove utilization rate is only about 1/3. It can be seen that the slotless winding can reduce the volume and weight of the motor, improve the utilization factor, and save a lot of expensive

Insulation material, and can reduce the loss in the stator teeth, and the additional loss caused by the rotor surface due to the presence of teeth, the economic benefits are significant. Secondly, the transient reactance is reduced, and electromagnetic vibration and noise due to cogging harmonics can be eliminated.

For decades, this type of air gap winding has not been used in conventional turbo generators because attention has been focused on developing the internal cooling technology of the winding to increase the ultimate capacity of the turbo generator. However, the use of slotless windings in superconducting turbine generators shows a clear trend.

Armature winding in superconducting steam turbine generator

For the "semi-" superconducting turbo generators in which the armature windings are still made of normal temperature copper and the rotor excitation windings are superconducting materials, the size of the air gap is no longer limited by the excitation power. Therefore, the air gap windings are completely available.


At present, the superconducting machine has two basic types of armature (air gap) windings, namely a spiral winding and a spiral flat winding, which are developed on the basis of the aforementioned slotted and slotless armature windings.

In addition to the characteristics of the conventional turbo generator air gap winding, since the superconducting field winding can establish a strong magnetomotive force, a strong air gap magnetic field is established at the coreless air gap armature winding, in the armature winding The medium can sense a very high electromotive force, and the conductor of the winding can be composed of a cable wrapped with transformer oil impregnated paper. Therefore, the superconducting machine becomes an ultra-high pressure turbo generator, which provides a promising prospect for power supply to the grid without using a step-up transformer.

Hollow winding of servo motor

As an actuator in a servo system, it is required to have a fast response speed, and a linear relationship between response and excitation is desired to simplify the control system. For this reason, the servo motor is required to have a small electromagnetic inertia and a mechanical inertia. Currently, the most common and effective method is to use an iron coreless armature winding, often called a hollow winding.

Reprinted from the network