Electrical generator or motor structure – Dynamoelectric – Rotary
Reexamination Certificate
1998-09-16
2002-08-27
Arbes, Carl J. (Department: 3729)
Electrical generator or motor structure
Dynamoelectric
Rotary
C310S216055, C310S254100, C310S261100
Reexamination Certificate
active
06441528
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method of expanding types of synchronous motors to obtain synchronous motors having different specification values with respect to torque and/or inertia, and synchronous motors produced by the method.
BACKGROUND ART
As an alternating-current motor, there is known a synchronous motor comprising a rotor having permanent magnets therein and a stator having windings thereon. In setting types of synchronous motors, motor characteristics of torque and rotor inertia are determined to have different specification values in series of motors, to thereby obtain expanded types of synchronous motors.
There are defined a variety of series such as a standard series having standard specification values of torque and rotor inertia, a low-inertia series having a small rotor inertia specification value relative to the torque specification value, and a high-torque series having a large torque specification value relative to the rotor inertia specification value, and motors in each series have output torque and rotor inertia values different from one another to be approximate multiples of that of the other one.
FIGS. 4
a
and
4
b
illustrate the arrangements of conventional synchronous motors, wherein
FIG. 4
a
shows the combination of a stator and a rotor for constructing a standard-series motor having standard specification values of torque and rotor inertia, and
FIG. 4
b
shows the combination of a stator and a rotor for constructing a low-inertia series motor having a smaller rotor inertia specification value.
In
FIG. 4
a
, a standard series synchronous motor
10
is constituted by combination of a stator
11
and a rotor
12
. The stator
11
comprises a stack of steel plates with an overall height H, each steel plate having a center hole
15
for receiving the rotor
12
therein and grooves
13
for fitting windings on an inner periphery of the hole
15
. The rotor
12
has a diameter h
1
, such that it can be inserted into the hole
15
of the stator
11
, and has permanent magnets
14
arranged circumferentially.
A low-inertia series synchronous motor
20
shown in
FIG. 4
b
is constituted by combination of a stator
21
and a rotor
22
. The stator
21
comprises a stack of steel plates with the overall height H, each steel plate having a center hole
25
for receiving the rotor
22
therein and grooves
23
for fitting windings on the inner periphery of the hole
25
. The rotor
22
has a diameter h
2
such that it can be inserted into the hole
25
of the stator
21
, and has permanent magnets
24
arranged circumferentially. To reduce the rotor inertia, the diameter h
2
of the rotor
22
is smaller than the diameter h
1
of the rotor
12
for the standard series, and the stator
21
also has a smaller inner diameter corresponding to the small diameter h
2
of the rotor
22
. Generally, the permanent magnets
14
and
24
used in the rotors of the conventional synchronous motors are made of a magnetic material such as ferrite.
Thus, the conventional synchronous motor has a construction such that one stator shape is associated with one type of rotor to be inserted into the stator, and the synchronous motor characteristics and the stator shape are in one-to-one relation. Each series of synchronous motors is therefore constructed by the selective combination of one of groups of stators having an identical sectional shape but different stack lengths, with rotors associated with the selected stator group.
FIGS. 5 and 6
illustrate a conventional method for expanding types of synchronous motor, wherein
FIG. 5
shows stator groups and rotor groups in the conventional method, and
FIG. 6
shows standard-series motors and low-inertia series motors constructed by combining the stator groups and the rotor groups.
In
FIG. 5
, the stator groups and the rotor groups are shown on the left-hand and right-hand sides of the figure, respectively. The stator groups consist of a large-diameter stator group including stators SA, SB, SC and SD having a large-diameter hole for receiving a rotor therein, and a small-diameter stator group including stators Sa, Sb and Sc having a small-diameter hole for receiving a rotor therein. For the rotor groups, two different outer diameters, that is, large and small outer diameters, are set in accordance with to the rotor inertia, and thus the rotor groups consist of a large-diameter rotor group including rotors RA, RB, RC and RD having large diameters, and a small-diameter rotor group including rotors Ra, Rb and Rc having small diameters. The stators and the rotors have their diameters and lengths set in accordance with characteristics of synchronous motors to be obtained.
The heights of the stators SA-SD and the rotors RA-RD are set to be multiples of L, i.e., L,
2
L,
4
L,
8
L, . . . and the heights of the stators Sa-Sc and the rotors Ra-Rc are set to be multiples of L, i.e., L,
2
L,
4
L, . . . .
To construct a plurality of series of synchronous motors using stator groups having respective identical sectional shapes and different stack lengths, stator-rotor combinations are selected from among the stator and rotor groups shown in
FIG. 5
in accordance with required synchronous motor characteristics, thereby obtaining synchronous motors of standard series and low-inertia series as shown in FIG.
6
. In
FIG. 6
, the right-hand side shows standard series motors having standard torque and rotor inertia specification values, and the left-hand side shows low-inertia series motors having relatively small rotor inertia specification values. Each series aligned in a column comprises stator-rotor combinations of which the torque values and inertia values are respectively different from one another to be multiples of a fundamental value.
For example, in a first row across the two series (the uppermost horizontal combination), a standard series motor has a rotor inertia specification value of J and a torque specification value of T. To construct a low-inertia series motor having a smaller rotor inertia specification value, a stator and a rotor both having a smaller diameter are selected and combined, whereby an expanded type of synchronous motor is obtained.
In the conventional method of expanding synchronous motor types, one stator shape is associated with one type of rotor to be inserted in the stator and the synchronous motor characteristics and the stator shape are in one-to-one relation, as stated above. Accordingly, to construct a series of synchronous motors using a group of stators having the same sectional shape but different stack lengths, as many stator types as the rotor types are required, giving rise to a problem that a large number of types of stators are needed.
The conventional method for expanding synchronous motor types also has a problem that when the stator height and the rotor length are changed in order to alter the torque specification value, the rotor inertia also changes with the change of the stator height and the rotor length.
TABLE 1
Table 1 above shows how respective torque and rotor inertia specification values are achieved by the standard series motors and the low-inertia series motors according to the conventional synchronous motor type expansion method. For example, a motor with the torque specification value T and the rotor inertia specification value J can be realized by a standard series type A, and a motor with the torque specification value T and the rotor inertia specification value J/
2
can be realized by a low-inertia series type a. In Table 1, symbols A to C and a to c affixed to the end of the respective series names denote motor types of which the stator-rotor combinations are shown in FIG.
6
.
Referring to Table 1, in the case where the torque specification value of the standard series type A is required to be changed to
2
T, such requirement can be satisfied by the standard series type B in the conventional synchronous motor type expansion method, as indicated by the broken-line arrow. However, in this case, not only the torque but the rotor inertia increases doubly,
Okamoto Takashi
Uchida Hiroyuki
Yamamoto Tomonaga
Arbes Carl J.
Fanuc Ltd.
Staas & Halsey , LLP
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