What Is a Unipolar Motor?

A unipolar motor armature is a type of DC motor with a metal disc (viewed as a combination of radial conductors) or a cylinder (viewed as an axial conductor combination). Viewed from one end of the armature, the magnetism is extremely unipolar, hence the name. When the magnetic induction wire and the armature of the armature conductor rotate, a radial or axial electromotive force with a constant direction is induced in the armature conductor. Suitable for low voltage, high current power supply equipment. In terms of reducing contact voltage drop and brush friction loss, liquid metal current collectors can be used. Superconducting unipolar motors have been developed.

Unipolar motor is passed

The earliest DC unipolar motor was . Barlou (. Barlou) in 1824 and M. M. Faraday was made in 1831. It is the simplest motor and generator.

These two types of motors are summarized in the following figures. In the 1980s of the last century, A. Forbest (A. Forbest) has studied the double-disc single-pole motor with electric excitation. Subsequently, A. A. Yale also proposed a hollow rotor unipolar generator.

Due to the wide application of different types of unipolar motors and the increasing number of new types, it is necessary to classify this type of motor in general. The classification based on the basic characteristics is shown in the figure below.

The basic structure of a superconducting unipolar motor is shown in the figure to the right. The magnetic field winding is a static DC superconducting magnet. The armature is a normal conductor. It is a rotating disk. The axis of the shaft and the magnetic field winding coincide.

Superconducting unipolar motor

When the disc rotates, it cuts the magnetic lines of force, generating a current and a potential drop in the radial direction. The current is drawn through a set of brushes. The unipolar motor is characterized by low voltage (only tens of volts) and high current (up to hundreds of thousands of amperes). . Conventional brushes cannot withstand such high currents and require special current-collecting materials.

The effect of the armature current on the magnetic field winding is simpler than that of a synchronous motor. When the load is stabilized, the magnetic field at each point of the armature current acting on the magnetic field winding does not change with time, so there is no adverse effect on the magnetic field winding, which needs to be considered. Only transient processes.

In order to ensure that the motor can still work normally during the transient process, the magnetic field winding should be wound with a braided wire or cable made of NbTi-Cu-CuNi composite wire (the diameter of the NbTi wire is 5 m). Experiments have shown that the rate of change of the transient magnetic field that such a wound magnetic field winding can withstand is very high.

Like synchronous motors, the economic cost of large superconducting unipolar motors is lower than conventional unipolar motors. The larger the capacity, the greater the savings. ^[3]