Rotor structure of line-start permanent magnet synchronous motor

Abstract

The invention provides a rotor structure of line-start permanent magnet (LSPM) synchronous motor that includes a shaft; four fan-shaped magnetic poles each having a first eccentric circular arcs of the surface of the magnetic poles which has a center O1 that is offset from the center O of the rotor with an offset length OS1 and which makes the maximum thickness of the air gap roughly two to five times as much as the minimum thickness of the air gap; four permanent magnets disposing in the inner loop of each of the fan-shaped magnetic poles□a plurality of pear-shaped conductor slots disposing in equal spaces in the outer loop of the rotor in each of the fan-shaped magnetic poles and orienting in radial direction having O1 as the center for forming a squirrel cage winding; as well as four recesses at the midpoint of the first eccentric circular arcs of the surface of the magnetic poles in each of the fan-shaped magnetic poles.

Description

FIELD OF THE INVENTION [0001] The invention relates to a rotor structure of a line-start permanent magnet synchronous motor, and more particularly, to a rotor structure of a hybrid type motor combining the merits of an induction motor and a synchronous motor, and being able to lower the cogging torque and to improve the starting characteristics of a motor. BACKGROUND OF THE INVENTION [0002] The line-start permanent magnet (LSPM) synchronous motor of the prior art is a hybrid motor with its stator structure being substantially the same as that of an AC induction motor or that of an AC synchronous motor. On the other hand, the rotor structure of this hybrid motor is a combination of the squirrel cage structure in the rotor of the AC induction motor and the permanent magnet structure in the rotor of the AC permanent magnet synchronous motor. When the stator of the LSPM synchronous motor is connected to the power source, a rotating magnetic field is generated by the stator, and an induc...

AI Technical Summary

Benefits of technology

[0016] One further objective of the invention described in the third embodiment of the invention is to provide a smooth curve of “the second eccentric circular arcs of the surface of the magnetic pole” to substitute the above-mentioned semi-circle recesses. In this way, the motor can adequately reduce the radial component distribution of the magnetic flux density of the air gap at the mid-way of the second eccentric circular arcs of the surface of the magnetic poles. Moreover, the motor can further reduce the cogging torque as well as the vibration and noise during the operation. What is more, the LSPM synchronous motor can slightly attenuate the magnetic f

Problems solved by technology

However, the cogging torque of the permanent magnet synchronous motor of the prior art becomes very large since the permanent magnet with high magnetic energy product is used.

As a result, the motor is subject to occurrence of operating vibration and noise.

Generally, the stator provides skew channels to improve the demerit, but the winding work of the stator becomes rather difficult. FIG. 1 is the U.S. Pat. No. 5,925,727, Boyd et al. of the prior art.

However, since the rotor does not have squirrel cage structure provided, the rotor cannot be line-started without utilizing some other devices.

But, as described before, since the rotor 13 is round in shape without special designed configuration, therefore, the cogging torque as well as the vibration and noise of the motor while the motor is in operation are still relatively large.

However, just how the curvature of the surface of the rotor varies is not explained anywhere in their specifications.

However, generally, among all the permanent magnets of rare earth metals having hi

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