Patent Publication Number: US-6700347-B1

Title: Speed varying device

Description:
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&gt;f 2  and further td 1 &gt;td 2  in order to keep a gradient of deceleration constant, so that it becomes Sad 11 &gt;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, and the axis of ordinate is a speed and fmax is the maximum frequency and fmin is the frequency at the time of low speed. Also, h 2 , h 3 , h 4  and h 5  are command positions of a deceleration stop command for making a stop in stop positions of the second floor, third floor, fourth floor and fifth floor at the time of rise. In an operation pattern at the time of fall, a direction differs but it becomes the similar movement, so that only the operation pattern at the time of rise was shown in the drawing. 
     In the elevator, generally, it is constructed so that sensors are mounted in an elevation passage of the elevator and a pass of a cage is detected to output a deceleration stop command. Deceleration stop command input positions (h 2 , h 3 , h 4  and h 5  in the drawing) which become points in time of this deceleration stop command are determined by a system of the elevator and for example, in the case of moving from the first floor to the third floor through fifth floor, the deceleration stop command is inputted during operation (h 3 , h 4 , h 5 ) at the maximum frequency fmax, but in the case of moving from the first floor to the second floor, the deceleration stop command is inputted during acceleration (h 2 ) (movement from the second floor to the third floor, movement from the third floor to the fourth floor and movement from the fourth floor to the fifth floor are also similar). 
     As described above, in the elevator, in order to make a stop in a stop position of each floor with accuracy, a moving distance at the time of deceleration from the deceleration start to the deceleration completion needs to be kept constant regardless of an operating frequency at a point in time of a deceleration stop command input, but when the conventional variable speed apparatus for decelerating by the deceleration time td 2  calculated by multiplying the reference deceleration time td 1  by a ratio between the operating frequency at the time of the deceleration stop command input and the adjustable speed reference frequency fstd is used in the case that the operating frequency at the time of the deceleration stop command input is different from the adjustable speed reference frequency fstd, there was a problem that the moving distance at the time of deceleration changes depending on the operating frequency at the point in time of the deceleration stop command input. 
     Also, in order to make a stop in a constant position regardless of an operating speed at a point in time when the deceleration stop command is inputted, by lengthening time for performing constant speed operation at the frequency fmin at the time of low speed or lengthening deceleration time more than the deceleration time td 2  calculated by multiplying the reference deceleration time td 1  by a ratio between the operating frequency at the time of the deceleration stop command input and the adjustable speed reference frequency fstd, the moving distance at the time of deceleration can be adjusted, but in this case, there was a problem that operating time at low speed becomes long. 
     Also, even when the S-shaped curve adjustable speed pattern for smoothing a change in speed at the time of start and stop is adopted, in the case that the deceleration stop command is inputted during acceleration, there was a problem that switching from linear acceleration to S-shaped curve deceleration is performed and a shock becomes large. 
     This invention is implemented to solve the problems described above, and a first object is to obtain a control method at the time of deceleration stop of a variable speed apparatus capable of making a stop in a constant position even when a deceleration stop command is inputted during acceleration. 
     Also, a second object is to obtain a control method at the time of deceleration stop of a variable speed apparatus capable of smoothly performing switching of speed change to deceleration when a deceleration stop command is inputted during acceleration. 
     DISCLOSURE OF THE INVENTION 
     A variable speed apparatus of this invention is constructed so that in a variable speed apparatus having a converter part for converting AC electric power into DC electric power, a smoothing capacitor for smoothing a DC voltage converted by this converter part, an inverter part for converting the DC electric power into AC electric power of a variable frequency, a variable voltage, and a control part for controlling the inverter part so as to make a deceleration stop after decelerating to a frequency at the time of low speed by deceleration time calculated by multiplying preset reference deceleration time by a ratio between an operating frequency at the time of deceleration stop command input and an adjustable speed reference frequency when a deceleration stop command is inputted, the control part comprises constant speed operating frequency calculation means for calculating a first constant speed operating frequency for performing constant speed operation when the deceleration stop command is inputted during acceleration, and constant speed operating time calculation means for calculating first constant speed operating time by the first constant speed operating frequency in order to equalize a moving distance at the time of deceleration from deceleration start to deceleration completion in the case that the deceleration stop command is inputted during acceleration to a moving distance at the time of deceleration from deceleration start to deceleration completion in the case that the deceleration stop command is inputted during operation at the adjustable speed reference frequency, and when the deceleration stop command is inputted during acceleration, operation is performed at the first constant speed operating frequency by the first constant speed operating time and then deceleration is performed to the frequency at the time of low speed by deceleration time calculated by multiplying the reference deceleration time by a ratio between the first constant speed operating frequency and the adjustable speed reference frequency. 
     Also, the control part comprises constant speed operating frequency correction means for calculating a second constant speed operating frequency for operating by constant speed operating holding time when the first constant speed operating time is longer than the constant speed operating holding time preset, and it is constructed so that when the deceleration stop command is inputted during acceleration and the first constant speed operating time calculated by the constant speed operating time calculation means is longer than the constant speed operating holding time preset, acceleration is further continued to the second constant speed operating frequency and operation is performed at the second constant speed operating frequency by the constant speed operating holding time and then deceleration is performed to the frequency at the time of low speed by deceleration time calculated by multiplying the reference deceleration time by a ratio between the second constant speed operating frequency and the adjustable speed reference frequency. 
     Also, the control part comprises deceleration time shortening means for determining the first constant speed operating time calculated by the constant speed operating time calculation means and shortening deceleration time calculated by multiplying the reference deceleration time by a ratio between the first constant speed operating frequency and the adjustable speed reference frequency in order to equalize a moving distance at the time of deceleration from deceleration start to deceleration completion in the case that the deceleration stop command is inputted during acceleration to a moving distance at the time of deceleration from deceleration start to deceleration completion in the case that the deceleration stop command is inputted during operation at the adjustable speed reference frequency when the first constant speed operating time becomes minus. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 is a diagram showing a configuration of a variable speed apparatus according to a first embodiment of this invention. 
     FIG. 2 is a diagram showing a control method of the variable speed apparatus according to the first embodiment of this invention. 
     FIG. 3 is a diagram showing a configuration of a variable speed apparatus according to a second embodiment of this invention. 
     FIG. 4 is a diagram showing a control method of the variable speed apparatus according to the second embodiment of this invention. 
     FIG. 5 is a diagram showing a configuration of a variable speed apparatus according to a third embodiment of this invention. 
     FIG. 6 is a diagram showing a control method of the variable speed apparatus according to the third embodiment of this invention. 
     FIG. 7 is a diagram showing a configuration of a conventional variable speed apparatus. 
     FIG. 8 is a diagram showing a control method of the conventional variable speed apparatus. 
     FIG. 9 is a diagram showing an operation pattern of an elevator. 
    
    
     BEST MODE FOR CARRYING OUT THE INVENTION 
     First Embodiment 
     FIG. 1 is a diagram showing a configuration of a variable speed apparatus according to a first embodiment of this invention. In the drawing, numerals  21  to  23 ,  26  are similar to those of FIG. 7 shown as a conventional example and the description is omitted. Numeral  1   a  is a variable speed apparatus, and numeral  2   a  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  3   a  is a control part for controlling an inverter part  23  based on various data set in the storage part  2   a  by a start command, a deceleration stop command and so on. 
     The control part  3   a  comprises constant speed operating frequency calculation means  11  for calculating a first constant speed operating frequency fout 1  obtained by S-shaped curve acceleration from a point in time when a deceleration stop command is inputted in the case that the deceleration stop command is inputted during acceleration, and constant speed operating time calculation means  12  for calculating first constant speed operating time tr 1  acting as time for performing constant speed operation at the first constant speed operating frequency fout 1  in order to equalize a moving distance at the time of deceleration in the case that the deceleration stop command is inputted during acceleration to a moving distance at the time of deceleration in the case that the deceleration stop command is inputted during operation at the adjustable speed reference frequency fstd. 
     FIG. 2 is a diagram showing a control method of the variable speed apparatus according to the first embodiment of this invention, and FIG.  2 ( a ) shows an operation pattern, and FIG.  2 ( 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 fout 1  is a first constant speed operating frequency calculated by the constant speed operating frequency calculation means  11  in the case that a deceleration stop command is inputted during acceleration. Also, 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 td 3  is deceleration time calculated by multiplying the reference deceleration time td 1  by a ratio between the first constant speed operating frequency fout 1  and the adjustable speed reference frequency fstd, and tr 1  is first constant speed operating time for performing constant speed operation at the first constant speed operating frequency fout 1  calculated by the constant speed operating time calculation means  12 . Also, A 1  is an operation pattern of the case that that a deceleration stop command is inputted during acceleration, and B is an operation pattern (similar to the operation pattern B of FIG. 6 of the conventional example) of the case that a deceleration stop command is inputted during operation at the adjustable speed reference frequency fstd, and also adjustable speed showed an example of S-shaped curve adjustable speed. 
     Also, a 1  and a 11  are points in time when a deceleration stop command is inputted, and g 1  is a point in time of S-shaped curve acceleration completion (a point in time of operation start at the first constant speed operating frequency fout 1 ), and h 1  is a point in time when deceleration is started after the first constant speed operating time tr 1  of constant speed operation at the first constant speed operating frequency fout 1 . Also, b 1 , c 1  and d 1  are way points of S-shaped curve deceleration in the operation pattern A 1 , and b 11 , c 11  and d 11  are way points of S-shaped curve deceleration in the operation pattern B. A range between a 1  and g 1  is a curve acceleration interval in an S-shaped curve adjustable speed pattern, and a range between h 1  and b 1 , a range between c 1  and d 1 , and a range between a 11  and b 11 , a range between c 11  and d 11  are curve deceleration intervals in the S-shaped curve adjustable speed pattern. Also, d 1  and d 11  are points in time of S-shaped curve deceleration completion, and e 1  and e 11  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, an action of the variable speed apparatus according to the first embodiment will be described by FIGS. 1 and 2. 
     An action of normal operation of performing variable speed control of accelerating to the adjustable speed reference frequency fstd by a start command and decelerating to the frequency fmin at the time of low speed by a deceleration stop command and making a deceleration stop by a stop command is similar to that of the conventional apparatus. 
     A moving distance Sad 11  at the time of deceleration from deceleration start to deceleration completion in the case of the operation pattern B in which a deceleration stop command is inputted during operation at the adjustable speed reference frequency fstd becomes expression (2) as shown in the conventional example described above. 
     
       
         Sad 11 =Sab 11 +Sbc 11 +Scd 11   expression (2) 
       
     
     Also, in an action of the case of the operation pattern A 1  in which a deceleration stop command is inputted during acceleration, when a deceleration stop command is inputted (a 1 ), acceleration is performed to the first constant speed operating frequency fout 1  obtained by S-shaped curve acceleration (g 1 ) and after the first constant speed operating time tr 1  of constant speed operation at the first constant speed operating frequency fout 1  (h 1 ), deceleration to the frequency fmin at the time of low speed is started. After deceleration is performed to the frequency fmin at the time of low speed between h 1  and d 1  by S-shaped curve deceleration, operation is performed at the frequency fmin at the time of low speed and when a stop command is inputted (e 1 ), a deceleration stop is made. 
     Also, when an area between a 1  and g 1  is set to Sag 1  and an area between g 1  and h 1  is set to Sgh 1  and an area between h 1  and b 1  is set to Shb 1  and an area between b 1  and c 1  is set to Sbc 1  and an area between c 1  and d 1  is set to Scd 1 , a moving distance Sad 1  at the time of deceleration from deceleration start to deceleration completion in the case of the operation pattern A 1  in which a deceleration stop command is inputted during acceleration becomes expression (4). 
     
       
         Sad 1 =Sag 1 +Sgh 1 +Shb 1 +Sbc 1 +Scd 1   expression (4) 
       
     
     In the pattern B in which the deceleration stop command is inputted during operation at the adjustable speed reference frequency fstd and the pattern A 1  in which the deceleration stop command is inputted during acceleration, in order to equalize the moving distances at the time of deceleration from deceleration start to deceleration completion, it is required that Sad 1 =Sad 11 . 
     Since the area Sgh 1  (between g 1  and h 1 ) of constant speed operation at the first constant speed operating frequency fout 1  is expressed by the product of the first constant speed operating frequency fout 1  and the time tr 1 , the first constant speed operating time tr 1  for performing constant speed operation at the first constant speed operating frequency fout 1  can be obtained by expression (5) from expression (2) and expression (4). 
     
       
         tr 1 =Sgh 1 /fout 1   expression (5) 
       
     
     Here, the Sgh 1  described above can be obtained as Sgh 1 =Sad 11 −(Sag 1 +Shb 1 +Sbc 1 +Scd 1 ) from expression (2) and expression (4). 
     Incidentally, in the above, an adjustable speed method has been described as S-shaped adjustable speed, but the similar effect can be obtained even in linear adjustable speed. In the case of the linear adjustable speed, in FIG. 1, it becomes a 1 =g 1 , h 1 =b 1 , a 11 =b 11 , c 1 =d 1  and c 11 =d 11 . 
     In the first embodiment, it is constructed so that when a deceleration stop command is inputted during acceleration, the first constant speed operating frequency fout 1  is calculated from an operating frequency at a point in time when the deceleration stop command is inputted in the constant speed operating frequency calculation means  11  and further the first constant speed operating time tr 1  for performing constant speed operation at the first constant speed operating frequency fout 1  is calculated in the constant speed operating time calculation means  12  and deceleration is performed after the first constant speed operating time tr 1  of constant speed operation at the first constant speed operating frequency fout 1  without performing deceleration immediately at a point in time when the deceleration stop command is inputted, so that even when the deceleration stop command is inputted during acceleration, switching of speed change to deceleration can be performed smoothly and also, a stop can be made in a constant position without lengthening deceleration time more than the deceleration time td 2  calculated by multiplying the reference deceleration time td 1  by a ratio between the operating frequency at the time of the deceleration stop command input and the adjustable speed reference frequency fstd, or operating at low speed by the frequency fmin at the time of low speed for a long time. 
     Second Embodiment 
     FIG. 3 is a diagram showing a configuration of a variable speed apparatus according to a second embodiment of this invention. In the drawing, numerals  11 ,  12 ,  21  to  23 ,  26  are similar to those of FIG. 1, and the description is omitted. Numeral  1   b  is a variable speed apparatus, and numeral  2   b  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, constant speed operating holding time tr 0 , and numeral  3   b  is a control part for controlling an inverter part  23  based on various data set in the storage part  2   b  by a start command, a deceleration stop command and soon. Here, the constant speed operating holding time tr 0  is limit operating time which does not feel long even when constant speed operation is performed at speed lower than the adjustable speed reference frequency fstd. 
     The control part  3   b  comprises constant speed operating frequency calculation means  11 , constant speed operating time calculation means  12  and constant speed operating frequency correction means  13  for comparing first constant speed operating time tr 1  calculated by the constant speed operating time calculation means  12  with the constant speed operating holding time tr 0  and calculating a second constant speed operating frequency fout 2  capable of operating by the constant speed operating holding time tr 0  to equalize a moving distance at the time of deceleration when the first constant speed operating time tr 1  is longer than the constant speed operating holding time tr 0 , and when the first constant speed operating time tr 1  is longer than the constant speed operating holding time tr 0 , after acceleration is performed to the second constant speed operating frequency fout 2  even after a deceleration command is inputted during acceleration, constant speed operation is performed at the second constant speed operating frequency fout 2  for the constant speed operating holding time tr 0  and deceleration is performed to a frequency at the time of low speed by deceleration time td 4  calculated by multiplying the reference deceleration time td 1  by a ratio between the second constant speed operating frequency fout 2  and the adjustable speed reference frequency fstd. Here, in the constant speed operating frequency correction means  13 , when a deceleration stop command is inputted during acceleration, the first constant speed operating time tr 1  calculated by the constant speed operating time calculation means  12  is compared with the constant speed operating holding time tr 0  preset and when the first constant speed operating time tr 1  is longer than the constant speed operating holding time tr 0 , the second constant speed operating frequency fout 2  (fout 1 &lt;fout 2 ≦fstd) capable of operating by the constant speed operating holding time tr 0  to equalize the moving distance at the time of deceleration is calculated. 
     FIG. 4 is a diagram showing a control method of the variable speed apparatus according to the second embodiment of this invention, and FIG.  4 ( a ) shows an operation pattern, and FIG.  4 ( b ) shows a state of a deceleration stop command and a stop command. In the drawing, fstd, fmin, fout 1 , td 3 , tr 1 , a 1 , g 1 , h 1 , b 1 , c 1 , d 1  and e 1  are similar to those of FIG.  2  and the description is omitted. Also, fout 2  is a second constant speed operating frequency. Also, tr 2  is operating time for performing constant speed operation at the second constant speed operating frequency fout 2  and is normally set to constant speed operating holding time tr 0 . Also, td 4  is deceleration time calculated by multiplying the reference deceleration time td 1  by a ratio between the second constant speed operating frequency fout 2  and the adjustable speed reference frequency fstd. Also, A 1  is an operation pattern (similar to the operation pattern A 1  of FIG. 2) of the case that that a deceleration command is inputted during acceleration, and A 2  is an operation pattern of the case that acceleration is performed to the second constant speed operating frequency fout 2  even after a deceleration command is inputted during acceleration. 
     Also, a 1  is a point in time when a deceleration command is inputted, and a 2  is a point in time of continuous acceleration completion, and g 2  is a point in time of S-shaped curve acceleration completion (a point in time of operation start at the second constant speed operating frequency fout 2 ), and h 2  is a point in time of S-shaped curve deceleration start, and b 2 , c 2  and d 2  are way points of S-shaped curve deceleration in the operation pattern A 2 . A range between a 2  and g 2  is a curve acceleration interval in an S-shaped curve adjustable speed pattern, and a range between h 2  and b 2  and a range between c 2  and d 2  are curve deceleration intervals in the S-shaped curve adjustable speed pattern. Also, d 2  is a point in time of S-shaped curve deceleration completion, and e 2  is a point in time when a stop command is inputted after constant speed operation at the frequency fmin at the time of low speed. 
     Calculation of the first constant speed operating frequency fout 2  will be described below. 
     When an area between a 1  and a 2  is set to Saa 2  and an area between a 2  and g 2  is set to Sag 2  and an area between g 2  and h 2  is set to Sgh 2  and an area between h 2  and b 2  is set to Shb 2  and an area between b 2  and c 2  is set to Scd 2  and an area between c 2  and d 2  is set to Scd 2 , a moving distance Sad 2  at the time of deceleration from deceleration start to deceleration completion in the case of the operation pattern A 2  in which a deceleration stop command is inputted during acceleration becomes expression (6). 
     
       
         Sad 2 =Saa 2 +Sag 2 +Sgh 2 +Shb 2 +Sbc 2 +Scd 2   expression (6) 
       
     
     Since the area Sgh 2  (between g 2  and h 2 ) of constant speed operation at the second constant speed operating frequency fout 2  is expressed by the product of the second constant speed operating frequency fout 2  and the operating time tr 2 , the second constant speed operating frequency fout 2  can be obtained by expression (7) from expression (2) and expression (6). 
     
       
         fout 2 =Sgh 2 /tr 2   expression (7) 
       
     
     Here, tr 2 =tr 0  and also, the Sgh 2  can be obtained as Sgh 2 =Sad 11 −(Saa 2 +Sag 2 +Shb 2 +Sbc 2 +Scd 2 ) from expression (2) and expression (6). 
     In the above, the description has been made by an example in which the constant speed operating holding time tr 0  is preset by parameter in the variable speed apparatus, but it may be constructed so that the constant speed operating holding time can be set corresponding to operating speed. 
     The first constant speed operating frequency fout 1 , which is calculated on the basis of an operating frequency at a point in time when a deceleration stop command is inputted as shown in the first embodiment, is equal to an operating frequency at a point in time when the deceleration stop command is inputted (for linear acceleration) or is somewhat higher than the operating frequency at a point in time when the deceleration stop command is inputted (for S-shaped curve acceleration), and in the case that the operating frequency at a point in time when the deceleration stop command is inputted is low, the first constant speed operating frequency fout 1  also becomes a low value. 
     In the second embodiment, it is constructed so that length of the first constant speed operating time tr 1  for performing constant speed operation at the calculated first constant speed operating frequency fout 1  is determined and when the first constant speed operating time tr 1  is longer than the constant speed operating holding time tr 0 , acceleration is continued to the second constant speed operating frequency fout 2  even after a deceleration command is inputted (a 1 ) as shown in the operation pattern A 2  and after the time tr 2  (tr 2 ≦tr 0 ) of constant speed operation at the second constant speed operating frequency fout 2 , deceleration is performed to the frequency fmin at the time of low speed by the deceleration time td 4 . 
     In the second embodiment, it is constructed so that when a deceleration stop command is inputted during acceleration (a 1 ), the first constant speed operating frequency fout 1  and the first constant speed operating time tr 1  are calculated and then, when the first constant speed operating time tr 1  is longer than the constant speed operating holding time tr 0 , the second constant speed operating frequency fout 2  (fout 2 &gt;fout 1 ) is calculated and acceleration is continued to the second constant speed operating frequency fout 2  even after the deceleration command is inputted during acceleration (a 1 ) and after the constant speed operating holding time tr 0  of constant speed operation at the second constant speed operating frequency fout 2 , deceleration is performed, so that a stop can be made in a constant position without operating at low speed for a long time even when the deceleration stop command is inputted during acceleration in which an operating frequency is low. 
     Third Embodiment 
     FIG. 5 is a diagram showing a configuration of a variable speed apparatus according to a third embodiment of this invention. In the drawing, numerals  11 ,  12 ,  21  to  23 ,  26  are similar to those of FIG. 1, and the description is omitted. Numeral  1   c  is a variable speed apparatus, and numeral  2   c  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, constant speed operating holding time tr 0 , deceleration lower limit time tmin, and numeral  3   c  is a control part for controlling an inverter part  23  based on various data set in the storage part  2   c  by a start command, a deceleration stop command and so on. 
     The control part  3   c  comprises constant speed operating frequency calculation means  11 , constant speed operating time calculation means  12  and deceleration time shortening means  14  for determining first constant speed operating time tr 1  calculated by the constant speed operating time calculation means  12  and shortening deceleration time when the first constant speed operating time tr 1  becomes minus. 
     A moving distance Sad 1  at the time of deceleration from deceleration start to deceleration completion in the case that a deceleration stop command is inputted during acceleration can be obtained as expression (4) as shown in the first embodiment described above. 
     
       
         Sad 1 =Sag 1 +Sgh 1 +Shb 1 +Sbc 1 +Scd 1   expression (4) 
       
     
     Also, the first constant speed operating time tr 1  for performing constant speed operation at a first constant speed operating frequency fout 1  can be obtained as expression (5) as shown in the first embodiment described above. 
     
       
         tr 1 =Sgh 1 /fout 1   expression (5) 
       
     
     Here, the Sgh 1  described above can be obtained as Sgh 1 =Sad 11 −(Sag 1 +Shb 1 +Sbc 1 +Scd 1 ) from Sad 1 =Sad 11 . 
     In the case that a point in time (a 1 ) when a deceleration stop command is inputted during acceleration is close to the adjustable speed reference frequency fstd, the first constant speed operating time tr 1  obtained by the expression (5) may become minus by movement in a curve acceleration interval (a 1  to g 1 ) and a constant speed operating interval (g 1  to h 1 ). In the case that the first constant speed operating time tr 1  becomes minus, a moving distance at the time of deceleration overshoots even though the first constant speed operating time tr 1  for performing constant speed operation at the first constant speed operating frequency fout 1  is set to zero. 
     FIG. 6 is a diagram showing a control method of the variable speed apparatus according to the third embodiment of this invention, and FIG.  6 ( a ) shows an operation pattern, and FIG.  6 ( b ) shows a state of a deceleration stop command and a stop command. In the drawing, fstd, fmin, td 1 , fout 1 , tr 1  and td 3  are similar to those of FIG.  2  and the description is omitted. Also, a 3  is a point in time when a deceleration command is inputted, and g 3  is a point in time of S-shaped curve acceleration completion (a point in time of operation start at the first constant speed operating frequency fout 1 ), and h 3  is a point in time when deceleration is started after the first constant speed operating time tr 1  of constant speed operation at the first constant speed operating frequency fout 1 . Also, b 3 , c 3  and d 3  are way points of S-shaped curve deceleration in an operation pattern A 3 . A range between a 3  and g 3  is a curve acceleration interval in an S-shaped curve adjustable speed pattern, and a range between h 3  and b 3  and a range between c 3  and d 3  are curve deceleration intervals in the S-shaped curve adjustable speed pattern. Also, d 3  is a point in time of S-shaped curve deceleration completion, and e 3  is a point in time when a stop command is inputted after constant speed operation at the frequency fmin at the time of low speed. 
     Also, when an area between a 3  and g 3  is set to Sag 3  and an area between g 3  and h 3  is set to Sgh 3  and an area between h 3  and b 3  is set to Shb 3  and an area between b 3  and c 3  is set to Sbc 3  and an area between c 3  and d 3  is set to Scd 3 , a moving distance Sad 3  at the time of deceleration from deceleration start to deceleration completion in the case of the operation pattern A 3  in which a deceleration stop command is inputted during acceleration is similar to expression (4) in the operation pattern A 1  shown in the first embodiment described above and becomes expression (8). 
     
       
         Sad 3 =Sag 3 +Sgh 3 +Shb 3 +Sbc 3 +Scd 3   expression (8) 
       
     
     Also, the first constant speed operating time tr 1  for performing constant speed operation at the first constant speed operating frequency fout 1  is similar to expression (5) shown in the first embodiment described above and can be obtained by expression (9). 
     
       
         tr 1 =Sgh 3 /fout 1   expression (9) 
       
     
     Here, the Sgh 3  described above can be obtained as Sgh 3 =Sad 11 −(Sag 3 +Shb 3 +Sbc 3 +Scd 3 ) from Sad 3 =Sad 11 . 
     In the case that tr 1 =0, Sgh 3 =0 and it becomes Sad 11 =Sag 3 +Shb 3 +Sbc 3 +Scd 3 , but Sag 3 , Shb 3  and Scd 3  are S-shaped curve adjustable speed portions and Sbc 3  is reduced (time of b 3  to c 3  is shortened) and thereby, a moving distance at the time of deceleration from deceleration start to deceleration completion is kept constant. Therefore, deceleration time td 5  needs to be shortened than deceleration time td 3  calculated by multiplying the reference deceleration time td 1  by a ratio between the first constant speed operating frequency fout 1  and the adjustable speed reference frequency fstd (td 3 &gt;td 5 &gt;deceleration lower limit time tmin). Here, the deceleration lower limit time tmin is time acting as a lower limit in the case of changing the deceleration time td 3  calculated by multiplying the reference deceleration time td 1  by a ratio between the first constant speed operating frequency fout 1  and the adjustable speed reference frequency fstd. 
     In the first embodiment described above, an example constructed so that deceleration is performed to the frequency fmin at the time of low speed by the deceleration time td 3  calculated by multiplying the reference deceleration time td 1  by a ratio between the first constant speed operating frequency fout 1  and the adjustable speed reference frequency fstd has been shown, but in the third embodiment, it is constructed so that when the first constant speed operating time tr 1  becomes minus, a moving distance is adjusted by shortening the deceleration time td 5  than deceleration time td 3  calculated by multiplying the reference deceleration time td 1  by a ratio between the first constant speed operating frequency fout 1  and the adjustable speed reference frequency fstd, so that a deceleration stop can be made smoothly even in the case that a speed at a point in time when a deceleration command is inputted is close to the adjustable speed reference frequency. 
     INDUSTRIAL APPLICABILITY 
     As described above, a control method at the time of deceleration stop of a variable speed apparatus according to the present invention is suitable for use in application for making a stop in a constant position like an elevator.