JP2001231293A - Synchronous motor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a synchronous motor which can be started by a simple control without using sensors for detecting the position of a rotor. SOLUTION: At least for a specified period of time from the start-up, the synchronous motor is driven with current carrying phase of windings for a field system of a stator switched sequently by means of an inverter to rotate a rotor. The synchronous motor comprises the inverter 5 for converting the frequency of a commercial power supply, a control section 2 for controlling the switching of the current carrying phases by the inverter 5, and a memory 10 which stores an operation pattern for controlling the switching operation of the inverter 5 as a setting table. When the motor is started up, the control section 2 controls the operation of the inverter 5 based on the operation pattern stored in the memory 10.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a commercial power supply voltage,
The present invention relates to a synchronous motor for rotating a rotor by sequentially switching an energized phase of a field winding of a stator by an inverter that performs frequency and power conversion.

[0002]

2. Description of the Related Art In a synchronous motor such as a permanent magnet motor or a reluctance motor, it is necessary to change the power supply frequency applied to the motor in accordance with the rotation speed. If the power supply frequency is significantly different from the motor rotation speed, synchronization is lost. Step-out state and cannot start. Therefore, the synchronous motor is generally driven using an inverter composed of a semiconductor element performing a switching operation as means for changing the power supply frequency. In addition, encoders and Hall elements,
The position of the rotor of the motor is detected using a current sensor or the like, and startup and speed adjustment are performed while continuously changing the switching frequency of the inverter in accordance with the detected position. Further, a method of starting without detecting a rotational position has been proposed. For example, Japanese Patent Laying-Open No. 5-68394 discloses a method in which an arbitrary function is provided for an operating frequency and an acceleration time, and a brushless motor is started without using sensors for detecting a position of a rotor.

[0003]

The above-mentioned sensors for detecting the position of the rotor are expensive, are vulnerable to shock or heat, and need to be added to the stator, so that they are required to be installed in a severe environment. It is difficult to mount the used motor in terms of reliability, and the control becomes complicated.

The present invention has been made to solve the above-described problems, and does not require sensors for detecting the position of a rotor, and can start a synchronous motor by simple control. It is an object to provide a synchronous motor.

[0005]

SUMMARY OF THE INVENTION A synchronous motor according to the present invention includes an inverter for converting the frequency and voltage of a commercial power supply. The rotor is rotated by sequentially switching the current-carrying phases (inverter drive), and after a lapse of a predetermined time, the rotor is rotated by supplying power directly from a commercial power supply without passing through an inverter (commercially available). It is a synchronous motor driven by a power supply (direct drive of a power supply), and includes storage means for storing an operation pattern for the inverter at a predetermined time from the start of the motor as a table.

[0006] In the above table, as an operation pattern,
The switching frequency of the current-carrying phase may include information on the increase in the frequency, the time during which the operation is maintained at the frequency, and the duty ratio when the switching element of the inverter is PWM-controlled.

[0007] In the table, an operation pattern may be set for each predetermined frequency range.

In the above table, the operation pattern may be set according to the load torque of the motor.

[0009] In the above operation pattern, the frequency is increased stepwise at a fractional frequency of the commercial frequency while referring to the phase of the commercial power supply, and the voltage is increased stepwise accordingly. An operation pattern in which the inverter is controlled so as to temporarily lower the voltage later may be used. The table may include information on a predetermined time from when the frequency is switched to when the voltage is reduced.

Further, the above-mentioned operation pattern is based on the assumption that, when switching from the inverter drive to the direct drive of the commercial power supply, the drive is switched to the direct drive of the commercial power supply via the inverter drive of the commercial frequency with reference to the phase of the commercial power supply. An operation pattern in which the switching frequency of the energized phase is continuously increased to an adjacent frequency that does not match the commercial frequency at an arbitrary phase without referring to the phase of the commercial power supply. Is also good.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The details of an embodiment of a synchronous motor according to the present invention will be described below with reference to the accompanying drawings.

FIG. 1 shows a synchronous motor according to an embodiment of the present invention. As the motor 7, a salient pole type permanent magnet embedded motor is used. FIG. 2 is a sectional view of a rotor of the motor,
The rotor has a permanent magnet 8 and an iron core (core) 9. The specifications of the motor are as follows: Capacity: 0.4 kW Number of phases: 3 Number of poles: 4 Number of slots: 6 Rotor diameter: 40 mmφ Core width: 50 mm Moment of inertia: 0.000012 kg · m 2.

Returning to FIG. 1, the synchronous motor comprises a motor 7 and a drive unit for driving the motor 7. The driving unit is
A control unit 2 having a DSP (digital signal processor), a rectifier circuit 4 of a three-phase bridge for rectifying an alternating current from the commercial power supply 1 to obtain a direct current, and controlling the rectified direct current by the control unit 2 It comprises a voltage type inverter 5 composed of an IGBT switch for obtaining an AC of an arbitrary frequency, and a drive power supply switching unit 6 for switching either the commercial power supply 1 or the inverter 5 to connect to the motor 7.

Rectifier circuit 4, inverter 5 and control unit 2
Is modularized. The drive power switching unit 6 is a magnet switch for switching the drive power to the motor 7, and switches the drive power to the motor 7 to the inverter 5.
Or, switch to the commercial power supply 1. The control unit 2 has a memory 10 for storing control parameters for the inverter 5. A commercial three-phase 200 V of 60 Hz is used for the commercial power supply 1, and power is supplied through a control module.

In the synchronous motor configured as described above, at an initial stage at the time of starting, the motor 7 is connected to the inverter 5 by the driving power supply switching unit 6, and the motor 7 is started using the inverter 5 as the driving power. When the motor 7 reaches the synchronous rotation, the driving power source is switched from the inverter 5 to the commercial power source 1 by the driving power source switching unit 6, and the motor 7 is driven using the commercial power source 1 directly as a power source. As described above, after reaching the synchronous operation after the start, the inverter is directly driven by the commercial power supply 1 and the use of the inverter 5 is stopped, so that the consumption of the inverter 5 can be reduced. It becomes possible. Hereinafter, the operation of the synchronous motor will be described in detail.

The DSP of the control unit 2 downloads a control program created in C language in advance, and sends a switching command for the IGBT to the inverter 5 by control based on this program. Thereby, the energized phases (U-phase, V-phase) of the three-phase winding of the stator of the motor 7 are
, W phase) is sequentially switched, the magnetic field on the stator side is rotated, and the rotor is rotated using the reluctance torque and the magnetic torque between the salient polarity on the rotor side of the motor 7 and the magnet.

In starting the motor 7, even if the energized phase is suddenly switched at the commercial power supply frequency of 60 Hz, the rotor does not rotate and the start fails. Therefore, in the present synchronous motor, at the time of startup, the motor 7 is driven while increasing the frequency stepwise from a low frequency by the inverter 5, and after reaching a stable rotation at 60 Hz, is switched to the direct drive by the commercial power supply. To

Specifically, first, the motor 7 and the inverter 5 are connected by the drive power supply switching unit 6, and the motor 5 is started by the inverter 5 at the switching frequency of the energized phase of 10 Hz. After reaching the time for stable rotation (time previously determined experimentally),
Switch frequency to 20 Hz. Then, similarly, 30,
The frequency is gradually increased to 40 and 50 Hz. By performing such control, a synchronous rotation of 60 Hz can be reached without any problem. After the synchronous rotation of 60 Hz is reached, the drive power source of the motor 7 is switched from the inverter 5 to the commercial power source 1 by the drive power source switching unit 6, and thereafter,
The motor 7 is supplied with electric power directly from the commercial power supply 1 and is driven at 60 Hz.

The switching frequencies of the energized phases are 10, 20, 3
When switching to each frequency of 0, 40, 50, and 60 Hz, the frequency is switched by sequentially switching the frequency where the voltage phase of the commercial power supply 1 and the zero-cross point coincide with each other as shown in FIG. It is possible to prevent loss of synchronism at the time, and to make the phase when the frequency finally reaches 60 Hz (synchronous rotation) coincide with the phase of the voltage of the commercial power supply 1.

The switching of the current-carrying phase at the time of startup is controlled by the control unit 2. The control unit 2 reads information necessary for control from the memory 10 and controls the inverter 5 to switch the switching frequency of the energized phase. Therefore,
Information (operation patterns) for setting control parameters for the switching elements of the inverter 5 at the time of startup is stored in the memory 10 as a table.

FIG. 4 shows an example of a control parameter setting table stored in the memory 10. The table is associated with information on the switching frequency, the increase in the frequency at the time of switching, the carrier frequency when performing PWM control of the inverter switching element, the duty ratio, and the time (holding time) during which operation is maintained at one frequency. ing. The table shown in FIG. 4 is set for each estimated torque, that is, an operation pattern that is sequentially switched for each estimated torque is set. Here, the estimated torque indicates a value obtained by estimating the load torque of the motor from the magnitude of the motor drive current. The motor drive current is a sensor (not shown) for overcurrent detection generally provided for overcurrent protection.
It can be easily estimated using. As the data set in the setting table, values obtained in advance by experiments or the like are used.

The control unit 2 performs control, for example, as follows with reference to such a table. If the estimated torque estimated from the motor drive current is 20% or less of the rating,
Starting with the operation pattern a-1, if the rotation of the rotor succeeds, the operation pattern is sequentially switched to a-2, a-3,. Finally, the frequency 60 is obtained according to the operation pattern a-6.
After operating at 80 Hz for 80 milliseconds, the driving power source is switched from the inverter 5 to the commercial power source 1 by the driving power source switching unit 6, and thereafter, the motor 7 is driven by the commercial power source 1. The start time from the start of the motor until the drive power supply is switched to the commercial power supply 1 is the total holding time, and in this case is about 1.2 seconds.

If the start fails in the operation pattern a-1, the engine is started in the operation pattern b-1 for the next largest load torque. If the start fails even in this operation pattern b-1, c-1 which is an operation pattern for a larger load torque is used. Thereafter, when failures continue, the operation pattern is switched to c-1, d-1, and e-1. In this way, by creating a table of the optimal operating conditions for each load torque value and automatically changing the operating pattern when starting is difficult, even if the load at the time of starting changes, the position can be changed. It is possible to start in an open loop without using a method of feeding back position information using a sensor, and it is possible to start reliably.

When the estimated torque estimated from the motor drive current is 20% to 40% of the rated value, the operation pattern b
−1, and if the activation is successful, b-2 to b
The operation pattern is switched to -12.

As described above, the operation is started by switching the operation pattern according to the estimated torque estimated from the motor drive current.

When the motor start-up is performed by referring to the voltage phase of the commercial power supply 1 to raise the switching frequency of the energized phase in a predetermined step-like manner and finally to 60 Hz, the rated voltage (200 V) from the start-up 100 for
% At the time of starting at a low frequency, instead of outputting a voltage of%, the switching operation of the IGBT is PWM-controlled to provide an off-time during the energization pattern to adjust the average voltage value of the inverter output. It is preferable to gradually increase the values from the values, and these control conditions are also included in the operation pattern. In this way, by increasing the average voltage in a stepwise manner as the frequency is switched,
It is possible to prevent an overcurrent that occurs instantaneously at the time of switching.

Further, the value of the table is set so that the increasing range of the frequency is increased in the low frequency region, the holding time is lengthened, and the increasing range is gradually reduced and the holding time is shortened in the high frequency region. You may. As a result, a smooth start can be obtained only by adjusting the average voltage on the low frequency side. In this case, the inverter output voltage and frequency are set as shown in FIG. The setting table at this time is the operation patterns a-1 to a-6. in this way,
In the control of the inverter 5, the control content can be easily changed only by changing the setting of the table. Further, FIG.
As shown in the figure, the output voltage (average voltage) of the inverter 5 increased with the switching of the frequency of the energized phase is changed for a predetermined time (t2, t4, t6, t6) from the time of switching the frequency of the energized phase.
8) The operation pattern may be set so as to drop once after the lapse. By controlling the output voltage of the inverter 5 in this manner, a sufficiently large difference between the output voltages of the inverter before and after the frequency switching can be ensured, and more stable operation can be performed at the time of frequency switching. At this time, the setting table further includes information on predetermined times (t2, t4,...) From the time of switching the frequency of the energized phase to the time of voltage drop.

The table values may be created for all the frequencies used. For example, the operation patterns c-1 to c-8, d-1 to d-8, and e-1 to e-8 shown in FIG.
As shown in FIG. 8, a frequency region may be determined, and each condition may be set within the frequency region. In this case, the size of the table can be reduced and the required memory size can be reduced as compared with the case where the value of the table is set for each frequency.

In general, a synchronous motor is provided with an overcurrent detection sensor for protecting a switch when an unsteady operation occurs. Therefore, a loop for turning off the IGBT switch by current feedback is provided. Is also good. Basically, it starts with the current set by the optimized table.

Further, as shown in FIG. 7, the synchronous motor may include a reference signal input section 3 for detecting the phase and frequency of the voltage of the commercial power supply 1 and taking it in as a reference signal. As a result, the control unit 2 can detect the phase and frequency of the voltage of the commercial power supply 1 and take it in as a reference signal.
When performing the control as shown in (1), while referring to the phase of the commercial power supply 1 based on the input signal from the reference signal input unit 3,
The frequency can be increased stepwise at the fractional frequency of the commercial power supply.

In the synchronous motor having the structure shown in FIG. 7, the start-up control may be performed as follows. That is, the synchronous motor is started based on an operation pattern in which the frequency is gradually increased at an arbitrary phase without referring to the voltage phase of the commercial power supply 1 for a predetermined time from the start. After the switching frequency reaches a nearby frequency (for example, 60 ± 1 Hz) that does not match the frequency of the commercial power supply (60 Hz), once the phase of the inverter output at that frequency matches the phase of the commercial power supply 1 Switching to inverter driving at 60 Hz, which is the commercial frequency with reference to the phase of the commercial power supply 1 (that is, inverter driving at the commercial frequency in phase with the commercial power supply), and then switching to direct driving with the commercial power supply 1. As described above, by switching from the inverter drive to the direct drive of the commercial power supply via the inverter drive of the commercial frequency with reference to the phase of the commercial power supply 1, a smooth start-up with reduced vibration can be realized.

In applications where torque fluctuations after starting are large, it is possible to provide a position sensor or the like and additionally use a function capable of following the fluctuations.

As described above, in this synchronous motor, since the motor 7 is started based on the control information stored in the memory 10 as a table, it is necessary to obtain the rotor position information of the motor 7 for determining the switching pattern. And the need for an angular position detection sensor or the like for detecting the position of the rotor of the motor 7 is eliminated, so that it is possible to improve the reliability and realize a synchronous motor that can be started by simple control. Further, the contents of the control can be easily changed only by changing the setting of the table.

[0034]

According to the synchronous motor of the present invention, since the inverter is controlled based on the operation pattern stored in the memory, a sensor or the like for detecting the position is not required, and the synchronous motor which can be started by simple control is provided. Can be provided. In addition, in the synchronous motor driven by the commercial power supply, the energized phase of the inverter is switched by sequentially switching the energized phase of the field winding of the stator by the inverter for a predetermined time from the start, and driving the rotor. Since a reference signal for performing control is not required, a means for generating such a reference signal is not required, and a synchronous motor can be realized with a simple configuration. Further, the control content can be easily changed only by changing the setting of the table.

The table has the following operating patterns:
For the switching frequency of the energized phase, the information may include information on the increase in the frequency, the time during which the operation is maintained at that frequency, and the duty ratio when the switching element of the inverter is subjected to PWM control. With this information, the inverter can be controlled freely.

Preferably, an operation pattern may be set for each predetermined frequency range in the table, so that the table size can be reduced.

Further, in the table, the operation pattern may be set in accordance with the load torque of the motor, so that even if the load torque is large, the operation pattern can be switched to the operation pattern in accordance with the load torque to further improve the operation pattern. Reliable motor starting is possible.

Further, the output voltage of the inverter which has been increased in accordance with the switching of the frequency of the energized phase may be controlled so as to temporarily decrease before the frequency of the next energized phase is switched. Can be ensured sufficiently large, and more stable operation can be performed at the time of frequency switching.

Further, when switching from the inverter drive to the direct drive of the commercial power supply, the drive may be switched to the direct drive of the commercial power supply via the inverter drive of the commercial frequency with reference to the phase of the commercial power supply. Reduced smooth startup is possible.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a synchronous motor according to the present invention.

FIG. 2 is a cross-sectional view of an example of a rotor of a synchronous motor.

FIG. 3 is a diagram for explaining a frequency switching operation at the time of startup.

FIG. 4 is a diagram illustrating a control parameter setting table for an inverter IGBT stored in a memory of a control unit;

FIG. 5: Inverter output voltage (average voltage) that changes stepwise as the switching frequency of the energized phase increases
FIG.

FIG. 6 is a diagram illustrating a state in which the inverter output voltage is stepwise increased while the output voltage is once decreased after the switching frequency of the energized phase is switched.

FIG. 7 is a diagram showing another configuration of the synchronous motor according to the present invention.

[Explanation of symbols]

1 commercial power supply, 2 control unit, 3 reference signal input unit,
4 rectifier circuit, 5 inverter, 6 drive power switching unit, 7 motor, 8 iron core, 9 magnet,
10 memory.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masaya Inoue 2-3-2 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Electric Corporation F-term (reference) 5H001 AA01 AB12 AC04 AD01 AE01 5H576 BB06 CC05 CC09 DD02 DD07 DD09 EE11 EE18 EE19 EE21 FF01 GG04 HA04 HB02 JJ03 KK06 LL22 LL38 LL39 LL53 MM09

Claims (6)

[Claims] An inverter for converting a frequency and a voltage of a commercial power supply to a predetermined value is provided, and at least for a predetermined time from start-up, the inverter sequentially switches the energizing phase of a field winding of a stator of a motor. After the lapse of the predetermined time, the synchronous motor is driven by the direct drive of the commercial power supply for rotating the rotor by supplying power directly from the commercial power supply without passing through the inverter after the predetermined time has elapsed by the inverter drive for rotating the rotor. And a storage means for storing, as a table, an operation pattern for the inverter at the predetermined time from the start of the motor as a table. 2. The table according to claim 1, wherein the operation pattern includes the following:
2. The synchronous motor according to claim 1, further comprising information on a time during which the operation is maintained at the frequency and a duty ratio when the switching element of the inverter is subjected to PWM control. 3. The synchronous motor according to claim 1, wherein the operation pattern is set for each predetermined frequency range in the table. 4. The synchronous motor according to claim 1, wherein the operation pattern is set in the table according to a load torque of the motor. 5. The operation pattern according to claim 1, wherein the frequency is increased stepwise at a fractional frequency of the commercial frequency while referring to the phase of the commercial power supply, and the voltage is increased stepwise in accordance with the frequency. 2. The synchronization pattern according to claim 1, wherein the operation pattern is for controlling the inverter to temporarily lower the voltage once, and the table includes information on a predetermined time from when the frequency is switched to when the voltage is reduced. motor. 6. The above operation pattern is based on the assumption that, when switching from inverter drive to direct drive of commercial power, the drive is switched to direct drive of commercial power via inverter drive at a commercial frequency with reference to the phase of the commercial power. The operation pattern shall be such that the switching frequency of the energized phase is continuously increased at an arbitrary phase to a frequency near the commercial frequency that does not match the commercial frequency without referring to the phase of the commercial power supply. The synchronous motor according to claim 1, wherein: