Abstract
This article describes a novel line-start type self-excited wound-field synchronous motor with three-phase concentrated winding stator. The unique feature of this proposed motor is that it accelerates by obtaining the starting torque from the slip frequency at the time of starting, and at the time of synchronous pull-in, it is driven synchronously with utilizing the second order space harmonic as the field magnetization power. This driving principle was verified by performing a load test using the prototype with two types of load, fan load and eddy current brake load. Consequently, the synchronization based on the proposed drive principle could be demonstrated on the actual machine, and the line-start characteristics of the proposed motor have been clarified.
Highlights
CONVENTIONALLY an induction motor (IM) capable of self-starting by directly connecting a commercial AC power supply has been widely used as a general-purpose industrial motor having a fan or a pump as a load due to a demand for cost reduction of its system
Efficiency can be improved by using a permanent magnet synchronous motor (PMSM) that does not require an excitation current, but an inverter is indispensable because a PMSM cannot in principle start by itself
For a general-purpose industrial motor that starts directly, the motor is accelerated by obtaining the starting torque from the slip frequency immediately after the line start, and is brushless to the rotor winding utilizing the second order space harmonic as the field energy source during synchronization
Summary
CONVENTIONALLY an induction motor (IM) capable of self-starting by directly connecting a commercial AC power supply has been widely used as a general-purpose industrial motor having a fan or a pump as a load due to a demand for cost reduction of its system. Efficiency can be improved by using a permanent magnet synchronous motor (PMSM) that does not require an excitation current, but an inverter is indispensable because a PMSM cannot in principle start by itself It has not been widely used in industrial applications from the viewpoint of system cost. An axialgap structure or dual stator structure has been studied for the purpose of improving the torque density of the PS-PMSM [9][11] This type of motor has high output and high efficiency at the time of synchronization. In addition to the need for an excitation current to obtain a field flux as in the case of the IM, it is difficult to reduce the armature copper loss due to the distributed winding stator structure.
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