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Skip to Main Content. A not-for-profit organization, IEEE is the world's largest technical professional organization dedicated to advancing technology for the benefit of humanity.
In general, control of speed with the alternating-current induction motor implies variable or adjustable frequency in some form, and this, in turn, involves a commutator of some type. In consequence, the problem of commutating alternating current usually goes hand in hand with that of speed control. The simplest method, according to the author, for viewing both the a-c.
In the d-c. In the same way, in the a-c. These latter may be classified as primary rotational and transformer e. One limitation in the design of a-c. However, the author contends that the commutation problem in a-c. The major part of the paper covers the consideration of the different e. In the latter part of the paper certain general conditions of commutation and brush operation are treated and some figures are given for comparison of a-c.
Article :. Date of Publication: March Need Help?
The situation was so bad that motors could not be designed ahead of the actual construction. The success or failure of a motor design is not known until it is actually built and tested. He formulated the laws of magnetic hysteresis in finding a solution. Hysteresis is a lagging behind of the magnetic field strength as compared to the magnetizing force. This produces a loss not present in DC magnetics. Low hysteresis alloys and breaking the alloy into thin insulated laminations made it possible to accurately design AC commutator motors before building.
A.C. Commutator Motors
A commutator is a rotary electrical switch in certain types of electric motors and electrical generators that periodically reverses the current direction between the rotor and the external circuit. It consists of a cylinder composed of multiple metal contact segments on the rotating armature of the machine. Two or more electrical contacts called " brushes " made of a soft conductive material like carbon press against the commutator, making sliding contact with successive segments of the commutator as it rotates. The windings coils of wire on the armature are connected to the commutator segments.
2-3-1. Structure and Characteristics of AC Commutator Motors
In Chapter 1, you have read about electromagnet-based DC motors. You have seen various connection methods there such as shunt, series, and separate field. Among these motors, what do you think will happen if AC power is applied to a series motor? Assume that when the motor is rotating in the condition shown in Fig. If the polarity of the electromagnet remains the same as shown in Fig.