JPH0648916B2 - Electric motor speed controller - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a speed control device for an electric motor, and more particularly to an electric motor suitable for a case where the magnitude of the load applied to the electric motor changes with a certain predetermined period. The present invention relates to a speed control device.

[Background of the Invention]

For example, as a method of varying the cooling or heating capacity of a room air conditioner, a method of controlling and changing the rotation speed of a compressor electric motor using an inverter has been generally used in recent years.

Therefore, the speed control range of these electric motors is about
It is about 2000 rpm to 6000 rpm.

If this speed control range is further expanded, the capacity control range of the room air conditioner will be expanded, the heating capacity will be enhanced for high speed rotation, and power saving and low noise for low speed rotation. Is obtained.

However, for low speed rotation of about 1000 rpm or less, vibration and noise increase conventionally due to the following reasons.
It was difficult to put it into practical use.

That is, a compressor used in a room air conditioner or a refrigerator generally has a structure in which it is sealed in a chamber together with a driving electric motor, and the load torque applied to the electric motor of the compressor is the same as that of a rotary compressor or a reciprocating compressor. Regardless of which one, there is a large pulsation with respect to the rotation angle, the maximum load torque reaches about three times the average load torque, and the cycle is repeated once for one rotation.

Here, FIG. 10 shows changes in the load torque T _L , the output torque T _M of the electric motor, and the rotation speed N with respect to the rotation angle of the electric motor.

In the rotation angle region of B in which the load torque T _L is larger than the output torque T _M , angular acceleration is generated by deceleration of the rotation speed N, and is represented by the product of the inertia moment J of the rotating shaft system of the electric motor. A rotational inertia torque is generated, and this and the output torque T _M are in balance with the load torque T _L.

On the other hand, in the region of A shown in the drawing, which is the rotation angle region of T _L <T _M , the rotational inertia torque is generated based on the increase in the rotation speed. That is, by generating the rotational inertia torque according to the torque difference of T _M −T _L , the electric motor on the output side,
Torque is balanced with the compressor as the load side.

In other words, in the electric compressor, rotation pulsation occurs during one rotation, which causes vibration and noise in the entire compressor chamber.

In particular, when the electric motor is driven to a low speed range, the rotational pulsation amplitude decreases as the rotational speed decreases, and the rotational pulsation frequency decreases for the same angular acceleration as at high speed. .

Then, the vibration caused by this also has a large amplitude according to the rotation pulsation, and the vibration frequency also decreases.

Therefore, conventionally, in order to expand the rotational speed range of the compressor electric motor in the low speed direction, vibration and noise are violent, and the vibration proofing and sound proofing measures become large in size, which is difficult to achieve at a practical level. It was

To solve the above problems, for example, the present inventors have
There is one related to Japanese Patent Application No. 59-123639 developed earlier,
The load torque pattern is stored in advance, and the stored torque pattern data is read for each rotation angle,
This is a torque control device developed to control the output torque.

However, in the above method, it is premised that the load torque pattern with respect to the rotation angle is known, and the known case is sufficient, but a point corresponding to an arbitrary load torque pattern, Has a point to be considered in that it is necessary to detect a reference position for the rotation angle.

[Object of the Invention]

The present invention, like the compressor, the speed of the load whose load changes in a certain fixed cycle, without detecting the reference position, the pulsation of the speed is reduced as much as possible, and it is possible to change in a wide range. It is an object of the present invention to provide a speed control device for an electric motor.

[Outline of Invention]

In order to match the speed of the load driven by the electric motor with the command speed, the voltage or current applied to the electric motor corresponds to the magnitude of the load applied to the electric motor changing during a predetermined cycle. In a speed control device of an electric motor including a device for controlling, a predetermined readable period is divided into n, and a readable / writable storage element that independently stores n pieces of data related to a voltage or a current applied to the electric motor is provided. The kth cycle of the predetermined cycle (k is a positive integer)
In n, the speed is detected for each of the n divided areas, and at least one data of the n pieces of data is corrected so as to equalize the speeds in the divided adjacent areas, and (k + 1) of the predetermined cycle. This is achieved by the configuration of controlling the voltage or current applied to the electric motor in the cycle, according to the data corrected in the cycle k.

Example of Invention

Each embodiment of the speed control device for an electric motor according to the present invention is
This will be described with reference to FIGS.

FIG. 1 is a configuration diagram of a speed control device for an electric motor according to an embodiment of the present invention, FIG. 2 is a detailed view of a current control unit thereof, and FIG.
FIG. 4 is an operation explanatory view thereof, FIG. 4 is a detailed configuration diagram showing the speed control thereof, FIG. 5 is an operation explanatory view thereof, and FIG. 6 is a speed control of an electric motor according to another embodiment of the present invention. FIG. 7 is a detailed configuration diagram showing speed control in the device, FIG. 7 is an operation explanatory diagram thereof, and FIG. 8 is a detailed configuration diagram showing speed control in a speed control device for an electric motor according to still another embodiment of the present invention. FIG. 9 is an explanatory diagram of the operation.

Therefore, each of the embodiments relates to an embodiment applied to a brushless DC electric motor related to a compressor electric motor as an electric motor.

That is, FIG. 1 shows the overall configuration of the speed control device for the brushless DC motor.

The illustrated DC voltage _Ed is obtained from the rectifier circuit 2 and the smoothing capacitor 3 from the illustrated AC power supply 1, and is supplied to the inverter 4.

This inverter 4 is a 120 ° conduction type inverter composed of transistors TR _{1 to} TR ₆ and free wheeling diodes D _{1 to} D _6, and its AC output voltage is DC voltage E.
_It is assumed that the conduction period (electrical angle 120 °) of the positive potential side transistors TR _{1 to} TR ₃ of _d is controlled by pulse width modulation and the chipper operation.

Moreover, in which low resistance _{R 1} is connected between the common anode terminal of the common emitter terminal of the transistor _TR 4 to Tr ₆ and the reflux diode _D 4 to D _6.

5 is a compressor section, which is related to a brushless DC motor
It is composed of a synchronous motor 5-1 having a pole permanent magnet as a field, and a compressor 5-2 which is a load body thereof.

Winding current flowing through the armature winding of the synchronous motor 5-1, wherein the well flow to a low resistance R _1, the voltage drop of the low-resistance R _1, in which the winding current I _L can be detected.

The control circuit configured to control the speed of the synchronous motor 5-1 includes a magnetic pole position detection circuit 6 for detecting the magnetic pole position of the rotor of the microcomputer 7, the synchronous motor 5-1 and the armature winding of the synchronous motor 5-1. A current controller 8 for controlling the line current, a base driver 9 for the transistors TR _{1 to} TR ₆ ,
And the speed of the synchronous motor 5-1 to the speed command NCM shown in the figure.
It is composed of a speed command circuit 12 which transmits to the microcomputer 7 as D.

The magnetic pole position detection circuit 6 uses a filter circuit based on the armature winding terminal voltages V _{A to} V _C of the synchronous motor 5-1.
It is a circuit that forms a position detection signal 6S corresponding to the rotor position. Then, using the position detection signal 6S, the rotational speed of the synchronous motor 5-1 is calculated by the microcomputer 7 and obtained.

However, in this embodiment, in order to reduce the velocity pulsation as much as possible, one means for equalizing the velocities of the adjacent regions is to make all the velocities of the divided regions match the command velocity. It was done.

In addition, the above-mentioned microcomputer 7 includes the CPU 7-1,
It is composed of a ROM 7-2, a RAM 7-3 and the like, which are connected by an address bus, a data bus and a control bus (not shown), respectively.

The ROM 7-2 stores various processing programs necessary to drive the synchronous motor 5-1 related to the brushless DC motor, such as those related to speed calculation processing, command fetch processing, speed control processing, and the like. There is.

On the other hand, the RAM 7-3 is related to a main memory unit 7-3a for reading and writing various data necessary for executing the various processing programs, and a winding current value to be passed for each rotor position. The current pattern storage section 7-3b stores the 12 pieces of current data.

Based on the current data in the current pattern storage unit 7-3b of the microcomputer 7, the current control unit 8 follows the winding output current I according to the current output data 11 output for each rotational position.
_It controls _L. In addition, 10 is a checker signal described later.

That is, in the brushless DC motor, the winding current flowing through the armature winding corresponds to the output torque of the motor, and by controlling the winding current for each rotational position, the output torque can be controlled for each rotational position. It will be.

FIG. 2 shows the details of the current control unit 8 described above.

That is, the D / A converter 17 as the current command circuit, the amplifier 13 as the current detection circuit, the current comparator 14 that compares the current command value 11a with the current detection value V _IL , the triangular wave oscillator 15, and the transistor TR ₁ described above. To TR ₃ and a comparator 16 for generating a checker signal 10 for operating the checker.

Current pattern storage unit 7-3b of the microcomputer 7
The 8-bit current output data 11 output to the outside of the microcomputer 7 based on the current data read out one by one from the 12 current data stored in Is converted into an analog quantity by the D / A converter 17 and becomes the illustrated current command value 11a.

Then, the winding current I _L obtained as the voltage drop of the low resistance R ₁ is amplified by the amplifier 13 and becomes the illustrated current detection value V _IL , and the current comparator 14 determines the above current command value 11 a. The output 14S and the triangular wave signal 15S, which is the output of the triangular wave oscillator 15, are compared by the comparator 16, and the output is the checker signal 1
0 is formed.

Then, FIG. 3 shows the position detection signal 6S and the current command value 1
It is operation | movement explanatory drawing which shows the time relationship with 1a.

Since the synchronous motor 5-1 is a 4-pole machine, (1) in the figure
One cycle of the position detection signal 6S representing the magnetic pole position of the rotor corresponds to a mechanical angle of 180 °, and for one rotation of the rotor 360 °, the illustrated mode “1” to the mode “1”.
It is divided into 12 modes every 30 ° up to 2 ".

Each of these modes is created by the method described later and stored in the current pattern storage unit 7-3b.
Two 8-bit current data are read according to each mode. The current output data 11 output based on the read current data is converted into the current command value 11a by the D / A converter 17 as shown in (2) of FIG. It

Then, as described above, the current detection value V _IL and the current command value 11a are compared to generate the checker signal 10, and the winding current I _L is controlled to have a waveform corresponding to the current command value. .

Next, an example of a method of correcting and outputting 12 pieces of current data stored in the current pattern storage unit 7-3b will be described.
This will be described below with reference to FIGS. 4 to 5.

FIG. 4 is a detailed block diagram showing in block form the processing contents of the microcomputer 7 in this embodiment.

The inputs are the position detection signal 6S from the magnetic pole position detection circuit 6 and the speed command NCMD from the speed command circuit 12.

In the speed calculation process 18, the speed is calculated from the rotation time of the rotor for each mechanical angle of 30 ° of the position detection signal 6S.

In the command fetching process 19, the speed command NCMD is read and the internal speed command INCMD is created.

The current pattern storage unit 7-3b described above is composed of the illustrated 12 integral terms I _{1 to} I ₁₂ related to the current data.

Here, I _i = Σ (INCMD−N _i ), and N _i is the rotation speed in the mode “i”.

On the other hand, the switches SW1 and SW2 are respectively
It shows which one of the two integral terms is selected for the input side and the output side, and switches between the two switches SW1 and SW2 each time the rotor rotates by a mechanical angle of 30 °. There is.

The integral term selected by the switch SW2 is subtracted by the proportional term P shown in the figure, and the current output data 11 is output to the D / A converter 17. Where the proportional term P
Is data obtained by multiplying the speed CURN calculated by the speed calculation processing 18 by K, that is, P = K · CURN.
Is.

Next, FIG. 5 shows that the detection speed is corrected in each mode from the mode “1” to the mode “12” divided every 30 ° among 360 ° of one rotation shown in FIG. 3 above. FIG. 7 is an operation explanatory view showing an integral term (that is, current data) and current output data.

At any given time t, the rotor position is in mode "i"
When the position is reached, the speed that can be detected in this mode "i" is the rotation speed N _i-1 in the immediately preceding mode "i-1" (mode "12" when i = 1). , The detected speed N _i-1 and the internal speed command IN at that time
The integral term I _i-1 is modified from CMD according to the following equation.

I _i-1 = (INCMD-N _i-1 ) + I _i-1 (1) Here, the integral term I _i-1 on the right side is the integral term up to that point in time, and is generally for the mode “i”. Integral term I
_i is obtained as follows.

I _i = Σ (INCMD−N _i ) ... (2) On the other hand, the current output data in the mode “i” has the integral term I _i and the proportional term P already corrected in the mode “i + 1” before one rotation. = KN _i−1 , I _i
-K · N _i-1 . Here, K is a proportional term gain.

As described above, 360 ° of one rotation is divided into 12 rotation positions of 30 °, and the integral term as the current data is independently readable and writable in the RAM area corresponding to the divided positions. , And the integral term at each rotational position is
As a result of creating from the difference between the speed at the rotational position and the command speed, one rotation 360 formed by 12 integral terms
The pattern of ° is similar to the pulsation pattern of compressive load.

Then, in the mode "i" corresponding to an arbitrary position, the processing of the microcomputer 7 is performed as described above.
The speed is calculated and the integral term is corrected in the mode "i-1" corresponding to the immediately preceding rotational position. Further, the current output data shows the integral term I _i and the integral term already corrected nearly one revolution before and its corresponding value. It is created and output from the proportional term P obtained from the speed calculated at the time point.

As described above, each of the twelve integral terms is corrected every one rotation, and the corrected integral term is corrected after one rotation.
Reflect on current output data. From this point, the response of the integral term is slow with respect to a sudden load.

On the other hand, in the above embodiment, the speed in the previous mode detected in a certain mode is reflected as a proportional term in the current output data, and the response of the above integral term is thereby obtained. Is compensated for, and as a result, the response of the current output data is made faster.

Next, another embodiment will be described with reference to FIGS. 6 to 7 as a method of creating current data stored in the current pattern storage unit. In the figure, the same reference numerals as those in FIGS. 4 and 5 are the same parts, 7-A is a microcomputer, 7-3b-
1 is a current pattern storage unit.

That is, the point different from the embodiment shown in FIGS. 4 and 5 is that the rotation speed in two modes with respect to one rotation of 12 modes, that is, in the period of a mechanical angle of 60 °. The point is that the current data is corrected based on the speed.

Therefore, FIG. 6 is a detailed block diagram showing the contents processed by the microcomputer 7-A in a block diagram similar to FIG.

That is, the difference between the internal speed command INCMD obtained from the command acquisition process 19 and the speed CURN calculated by the speed calculation process 18 at every mechanical angle of 30 ° results in the two current data. In addition to correcting the integral term, one integral term is reflected in the current output data.

Similar to FIG. 5, FIG. 7 shows the measurement period of the target speed to be detected, the content of the detected speed, the integral term as the current data to be corrected, and the current output in each of the 12 modes for one rotation. It is operation | movement explanatory drawing which showed the data.

The speed that can be detected in a given mode "i" is the same as the mode "i-1" and "i-2" (when i = 1, the modes "11" and "12", and i = 2). Is the speed N _(i-2)-(i-1) in modes "12" and "1".), And the detected speed N _(i-2)-(i-1) at that time The two integral terms are corrected according to the following equation from the internal speed command INCMD in.

I _i-2 = (INCMD-N _(i-2)-(i-1) ) + I _i-2 (3) I _i-1 = (INCMD-N _(i-2)-(i-1) ) + I _i-1 (4) Here, the integral terms I _i-2 and I _{i-1 on the} right side in the above equations
Is the mode "i" up to that point, as in equation (1) above.
-2 "and the mode" i-1 "are integral terms.

On the other hand, the current output data 11 in the mode “i” is already in the mode i + 1 ”and the mode“ i + ”up to that point.
2 ″ corrected by the integral term I _i and proportional term P = K · N
The difference between _(i-2)-(i-1) is I _i -K · N _(i-2)-(i-1) .

As described above, in the second embodiment shown in FIGS. 6 to 7,
The time of every 30 ° of the position detection signal 6S used for speed detection depends on the accuracy of the components that form the magnetic pole position detection circuit 6, and if the speed is not reflected correctly only every 30 °, then every 60 °. The speed detection is performed with high accuracy based on the time of, and the two integration terms are corrected to reduce the influence of the component accuracy on the current output data.

Therefore, in order to obtain the same effect as the above in the present embodiment, one integral term may be corrected and two integral terms may be reflected in the current output data.

That is, in the mode "i", the integral term to be corrected is
Only I _i-2 is selected, and _two integral terms, I _i and I _i-1 , which are reflected in the current output data are selected, and the current output data is set to (I _i
Even if + I _i-1 ) -K · N _(i-2)-(i-1) , the same effect can be obtained.

Furthermore, as a method of correcting and outputting the current data stored in the current pattern storage unit, another embodiment, that is, the third embodiment, will be described with reference to FIGS.
It will be described with reference to the drawings.

In the figure, the same symbols as those in FIGS. 4 and 5 above are the same parts,
7-B is a microcomputer, and 7-3b-2 is a current pattern storage unit.

That is, the difference from each of the embodiments shown above is that, in addition to the integral term, 12 proportional terms are prepared as the current data, and the integral term and the proportional term are paired corresponding to each of the 12 modes. This is the point that the number of current data is 12.

Thus, FIG. 8 is a detailed block diagram showing the contents processed by the speed control microcomputer 7-B, as in FIG.

That is, 12 integral terms I _{1 to} I ₁₂ and 12 proportional terms P _{1 to} P ₁₂ are respectively paired to form a current pattern storage unit 7-3b-2 with 12 current data. Is.

Then, the pair of the proportional term and the integral term is corrected by the switch SW1 for each rotation position of 30 °, and the pair of proportional term and integral term is selectively changed by the switch SW2 as the current output data 11 to the microcomputer 7-B. Is output more.

Similar to FIG. 5, FIG. 9 shows the detected speed, the integral term of the proportional term as the current data to be corrected in each of the modes “1” to “12” with respect to the rotational position at every 30 °, and , Is an operation explanatory view showing current output data.

The speed that can be detected in the mode "i" is N _i-1 (i =
When it is 1, N ₁₂ ), and the proportional term P _i-1 is created from the detected speed N ₁₂ and the internal speed command INCMD at that time according to the following equation.

P _i-1 = K (INCMD-N _i-1 ) where K is the gain of the proportional term.

On the other hand, the integral term I _i-1 is corrected in the same manner as the equation (1) in the embodiment shown above.

The current output data output in the mode “i” is I _i + P _i as the sum of the integral terms I _i and P _i that have been corrected in the mode “i + 1” before one rotation.

In the present embodiment described above, the proportional term is created based on the speed in the same mode as the integral term. Therefore, the current output data 11, in other words, the current command value which is the analog amount thereof, that is, the motor output torque is obtained. The accuracy of approximation of the pattern per one rotation and the pulsating pattern of the compressor load is improved, and the speed pulsation reducing effect is high.

According to each of the embodiments described above, the brushless DC motor is used as the compressor motor, and the speed control of this motor is performed. Therefore, the following effects can be summarized in summary. is there.

(1) With one rotation as a cycle, the rotation position is set to 1 every 30 ° with respect to the pulsating load pattern that is almost determined by the rotation position.
It is divided into two, and the speed is detected for each divided rotational position.
From the difference with the command speed, the current data related to the current is stored in a readable / writable RAM while being corrected, and the current of the brushless DC motor is controlled according to the stored current data, that is, because the output torque is controlled, The output torque pattern with one rotation cycle is the pulsating load pattern
The pattern is similar to 12 divisions.

As a result, the difference torque between the load torque of the compressor and the output torque of the electric motor is reduced, and the speed pulsation generated by the difference torque is reduced.

As a result, even if the compressor motor is expanded to a low speed motion range of 1,000 rpm or less, an electric compressor with less vibration can be obtained.

(2) Further, as described above, the output torque pattern of the motor is generated by the configuration that only uses the rotor magnetic pole position detection signal obtained from the armature winding terminal voltage to create the output torque pattern of the motor. In order to match the load torque pattern to the rotation angle, it is not necessary to provide a sensor for detecting the rotation reference position or a tachogenerator or encoder for detecting the speed and a sensor on the electric motor side. The reliability is improved without increasing the number of points.

Thus, although the above-mentioned embodiments relate to the brushless current electric motor related to the electric motor for the compressor as the electric motor, the present invention is not limited to this, for example, a certain predetermined value. During the cycle, the load of the load driven by the electric motor changes, and moreover, the change in speed during the predetermined cycle can be detected, and the speed can be controlled by controlling the current or voltage applied to the electric motor. It is a general-purpose device that can be used as a speed control device for an electric motor equipped with the device.

In addition, in each of the above-mentioned embodiments, the current applied to the electric motor is controlled, but this is the control of the number of revolutions, and the voltage control is performed as a configuration for controlling the voltage applied to the electric motor. Can be related to.

Furthermore, in the above-mentioned embodiment, the inverter device is used as the current control device, but this can be used as the tipper device in the DC power supply, and the same applies when both are used as the voltage control device. .

〔The invention's effect〕

As described above, according to the present invention, in response to the magnitude of the load applied to the electric motor changing in a predetermined cycle, the speed of the load body driven by the electric motor is added to the electric motor to match the commanded speed. A speed control device for an electric motor including a device for controlling a voltage or a current, which is a readable / writable memory that divides the predetermined cycle into n and independently stores n pieces of data related to the voltage or the current applied to the electric motor. At least one of the n pieces of data is provided so as to detect a velocity for each of the n divided regions in the k-th period of the predetermined period and equalize the velocity in the divided adjacent regions. To correct the voltage or current applied to the electric motor in the (k + 1) th cycle of the predetermined cycle according to the data corrected in the kth cycle. Since it has been made, it is possible to obtain a speed control device of the electric motor, which is suitable for changing the speed of the electric motor to a wide range according to the command speed, and particularly to minimize the speed pulsation in the low speed region, and also to implement the present invention. In this case, it is possible to realize it only by detecting the speed without detecting the reference position where the load body moves, and by knowing the change amount of the load that changes during a predetermined period in advance by creating an estimated load torque pattern. It is possible to provide a speed control device for an electric motor that is not necessary.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a speed control device for an electric motor according to an embodiment of the present invention, FIG. 2 is a detailed view of a current control unit thereof, and FIG.
FIG. 4 is an operation explanatory diagram thereof, FIG. 4 is a detailed configuration diagram showing the speed control thereof, FIG. 5 is an operation explanatory diagram thereof, and FIG. 6 is a speed control of an electric motor according to another embodiment of the present invention. FIG. 7 is a detailed configuration diagram showing speed control in the device, FIG. 7 is an operation explanatory diagram thereof, and FIG. 8 is a detailed configuration diagram showing speed control in a speed control device for an electric motor according to still another embodiment of the present invention. FIG. 9 is an explanatory diagram of the operation, and FIG. 10 is an explanatory diagram showing changes in the load torque, the output torque of the electric motor, and the rotational speed with respect to the electric motor and the rotation angle. 1 ... AC power supply, 2 ... Rectifier circuit, 3 ... Smoothing capacitor, 4 ... Inverter, 5 ... Compressor section, 5-1 ... Synchronous motor, 5-2 ... Compressor, 6 ... Magnetic pole Position detection circuit, 7, 7-A, 7-B ... Microcomputer, 7
-1 CPU, 7-2 ROM, 7-3 RA
M, 7-3a ... Main storage unit, 7-3b, 7-3b-1,
7-3b-2 ... current pattern storage section, 8 ... current control section, 9 ... base driver, 12 ... speed command circuit, 1
3 ... Amplifier, 14 ... Current comparator, 15 ... Triangular wave oscillator, 16 ... Comparator, 17 ... D / A converter,
18 ... Speed calculation processing, 19 ... Command acquisition processing, NCM
D: Speed command.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kenichi Iizuka, No. 800 Tomita, Ohira-cho, Shimotsuga-gun, Tochigi Prefecture Inside the Tochigi Plant, Hitachi, Ltd. (56) Reference JP-A-55-34836 (JP, A) -15494 (JP, U)

Claims (3)

[Claims] 1. A voltage applied to the electric motor to match the speed of a load driven by the electric motor with a command speed in response to the magnitude of the load applied to the electric motor changing during a predetermined period, or In a speed control device for an electric motor, which comprises a device for controlling a current, a voltage applied to the electric motor by dividing the predetermined cycle into n
Alternatively, it is provided with a readable / writable storage element for independently storing n pieces of data relating to the current, and k of the predetermined cycle.
At the cycle (k is a positive integer), the speed is detected for each of the n divided areas, and at least one of the n pieces of data is corrected so that the speed is equal in the divided adjacent areas. In the (k + 1) th cycle of the predetermined cycle, the speed control device for the electric motor is configured to control the voltage or the current applied to the electric motor according to the data corrected in the kth cycle. . 2. A speed control device for an electric motor according to claim 1, wherein the electric motor is an AC electric motor, and a device for controlling a voltage or a current applied to the electric motor is an inverter device. 3. The number of phases of the synchronous motor according to claim 1, wherein the electric motor is an alternating current motor, and the alternating current motor is a synchronous motor having a permanent magnet as a field. A motor speed control device in which the number represented by the product of the number of poles and the number of poles is the number of divisions.