Electricity: motive power systems – Induction motor systems – Braking
Reexamination Certificate
2002-08-12
2004-03-02
Masih, Karen (Department: 2837)
Electricity: motive power systems
Induction motor systems
Braking
C318S727000, C318S807000, C318S801000
Reexamination Certificate
active
06700347
ABSTRACT:
TECHNICAL FIELD
This invention relates to a variable speed apparatus for performing variable speed control of an induction motor.
BACKGROUND ART
FIG. 7
is a diagram showing a configuration of a conventional variable speed apparatus. In the drawing, numeral
20
is a variable speed apparatus, and numeral
21
is a converter part for converting AC electric power R, S, T from a three-phase AC power source into DC electric power, and numeral
22
is a smoothing capacitor for smoothing a DC voltage converted by the converter part
21
, and numeral
23
is an inverter part for converting the DC electric power into AC electric power U, V, W of a variable frequency, a variable voltage. Also, numeral
24
is a storage part for storing data such as adjustable speed patterns of linear adjustable speed or S-shaped curve adjustable speed, etc. set by parameters, an adjustable speed reference frequency fstd, a frequency fmin at the time of low speed, reference acceleration time ta
1
for accelerating from 0 Hz to the adjustable speed reference frequency fstd, reference deceleration time td
1
for decelerating from the adjustable speed reference frequency fstd to the frequency fmin at the time of low speed, and numeral
25
is a control part for controlling the inverter part
23
based on various data set in the storage part
24
by a start command, a deceleration stop command, etc. and numeral
26
is a motor. Here, the adjustable speed reference frequency fstd is a frequency based in order to calculate a gradient of adjustable speed, and the maximum value of an operating frequency is normally set.
In the conventional variable speed apparatus
20
, the adjustable speed patterns, the reference acceleration time ta
1
, the adjustable speed reference frequency fstd, the reference deceleration time td
1
, the frequency fmin at the time of low speed, etc. are preset by parameters, and when a start command is inputted, acceleration is performed by the reference acceleration time ta
1
to an operating frequency (=adjustable speed reference frequency fstd) commanded by the adjustable speed patterns set, and constant speed operation is performed at the operating frequency (=adjustable speed reference frequency fstd). During the constant speed operation, when a deceleration stop command is inputted, there is performed variable speed control in which deceleration is performed by the reference deceleration time td
1
to the frequency fmin at the time of low speed by the adjustable speed patterns set and constant speed operation is performed at the frequency fmin at the time of low speed and then a deceleration stop is made by an input of a stop command. Among these, the reference acceleration time ta
1
is set as reference acceleration time for accelerating from 0 Hz to the adjustable speed reference frequency fstd and also, the reference deceleration time td
1
is set as reference deceleration time for decelerating from the adjustable speed reference frequency fstd to the frequency fmin at the time of low speed. When an operating frequency targeted at the time of acceleration is different from the adjustable speed reference frequency fstd, acceleration time ta
2
is calculated by multiplying the reference acceleration time ta
1
by a ratio between the operating frequency targeted at the time of acceleration and the adjustable speed reference frequency fstd, and also when an operating frequency at the time of input of a deceleration stop command is different from the adjustable speed reference frequency fstd, deceleration time td
2
is calculated by multiplying the reference deceleration time td
1
by a ratio between the operating frequency at the time of input of a deceleration stop command and the adjustable speed reference frequency fstd.
FIG. 8
is a diagram showing a control method of the conventional variable speed apparatus, and FIG.
8
(
a
) shows an operation pattern, and FIG.
8
(
b
) shows a state of a deceleration stop command/stop command. In the drawing, fstd is an adjustable speed reference frequency, and fmin is a frequency at the time of low speed, and td
1
is reference deceleration time for decelerating from the adjustable speed reference frequency fstd to the frequency fmin at the time of low speed, and B is an operation pattern of the case that a deceleration stop command is inputted during operation at the adjustable speed reference frequency fstd, and C is an operation pattern of the case that a deceleration stop command is inputted during acceleration. Also, f
2
is a frequency at a point in time when a deceleration stop command is inputted in the operation pattern C, and td
2
is deceleration time calculated by expression (1).
td
2
=(f
2
/fstd)×td
1
expression (1)
The deceleration time td
2
is calculated by expression (1) and in the case of linear deceleration, a gradient of deceleration becomes constant and in the case of S-shaped curve deceleration, the gradient of deceleration does not necessarily become constant since a deceleration pattern is again recalculated on the basis of the deceleration time td
2
calculated by expression (1) and the operating frequency f
2
at the time of deceleration.
Also, in the drawing, an example of an S-shaped curve adjustable speed pattern for smoothing a change in speed at the time of start and stop was shown. a
11
and a
12
are points in time when a deceleration stop command is inputted, and b
11
, c
11
and d
11
are way points of S-shaped curve deceleration in the operation pattern B, and b
12
, c
12
and d
12
are way points of S-shaped curve deceleration in the operation pattern C. A range between a
11
and b
11
, a range between c
11
and d
11
, and a range between a
12
and b
12
, a range between c
12
and d
12
are curve deceleration intervals in the S-shaped curve adjustable speed patterns. Also, d
11
and d
12
are points in time of completion of the S-shaped curve deceleration, and e
11
and e
12
are points in time when a stop command is inputted after constant speed operation at the frequency fmin at the time of low speed.
Next, deceleration operation patterns of the conventional variable speed apparatus will be described.
In the case of the operation pattern B, when an area between a
11
and b
11
is set to Sab
11
and an area between b
11
and c
11
is set to Sbc
11
and an area between c
11
and d
11
is set to Scd
11
and a moving distance at the time of deceleration from a point a
11
in time of deceleration start to a point d
11
in time of deceleration completion is set to Sad
11
, the moving distance Sad
11
at the time of deceleration in the case of the operation pattern B becomes expression (2).
Sad
11
=Sab
11
+Sbc
11
+Scd
11
expression (2)
Also, in the case of the operation pattern C, when an area between a
12
and b
12
is set to Sab
12
and an area between b
12
and c
12
is set to Sbc
12
and an area between c
12
and d
12
is set to Scd
12
and a moving distance at the time of deceleration from a point a
12
in time of start to a point d
12
in time of deceleration completion is set to Sad
12
, the moving distance Sad
12
at the time of deceleration in the case of the operation pattern C becomes expression (3).
Sad
12
=Sab
12
+Sbc
12
+Scd
12
expression (3)
Here, when the moving distance Sad
11
at the time of deceleration in the case of the operation pattern B in which the deceleration stop command is inputted during operation at the adjustable speed reference frequency fstd is compared with the moving distance Sad
12
at the time of deceleration in the case of the operation pattern C in which the deceleration stop command is inputted during acceleration, it becomes fstd>f
2
and further td
1
>td
2
in order to keep a gradient of deceleration constant, so that it becomes Sad
11
>Sad
12
.
FIG. 9
is a diagram showing an operation pattern of an elevator. In the drawing, the axis of abscissa is a position and shows stop positions of the first floor, second floor, third floor, fourth floor and fifth floor, an
Sakurai Hisao
Shiraishi Yasuhiro
LandOfFree
Speed varying device does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Speed varying device, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Speed varying device will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3273166