JP7160662B2 - motor assembly - Google Patents

Description

The present invention relates to an electric motor assembly in which an inverter and an electric motor are integrated.

A motor assembly in which an inverter and a motor are integrated is used as a drive source for rotating machines such as pumps. In a mechanical system incorporating an electric motor assembly, resonance occurs when the rotational speed matches the natural frequency of the mechanical system, generating large vibrations and noise. Therefore, the inverter is provided with a frequency jump function to avoid resonance.

A frequency jump is a function of avoiding a frequency jump band in which resonance can occur to drive a motor. Setting of the frequency jump band is performed as follows. A vibration sensor is installed in the electric motor assembly, and the natural frequency is determined based on the vibration peak (maximum value) while gradually changing the rotation speed of the motor (that is, the output frequency of the inverter). input to the inverter. The inverter sets a frequency jump band centered on the input natural frequency and stores it in the storage device.

5 and 6 are graphs illustrating frequency jumps. The vertical axis represents the output frequency of the inverter, and the horizontal axis represents the command frequency input to the inverter. As shown in FIG. 5, when the command frequency rises and reaches the frequency jump band, the output frequency of the inverter is fixed at the lower limit value L of the frequency jump band. While the rising command frequency is within the frequency jump band, the output frequency of the inverter is maintained at the lower limit L of the frequency jump band. When the command frequency exceeds the frequency jump band, the output frequency of the inverter returns to the same frequency as the command frequency.

As shown in FIG. 6, when the command frequency decreases and reaches the frequency jump band, the output frequency of the inverter is fixed at the upper limit value H of the frequency jump band. While the decreasing command frequency is within the frequency jump band, the output frequency of the inverter is maintained at the upper limit value H of the frequency jump band. When the command frequency falls below the frequency jump band, the inverter output frequency returns to the same frequency as the command frequency.

Such a frequency jump function allows the inverter to rotate the motor while avoiding frequency bands in which resonance may occur. Therefore, it is possible to prevent resonance of the mechanical system in which the inverter and the electric motor are incorporated.

JP-A-10-336946 Japanese Patent Publication No. 2008-536467 JP 2016-111793 A

The natural frequency of a mechanical system incorporating an inverter and an electric motor can vary depending not only on the mechanical system itself but also on attachments such as piping fixed to the mechanical system. For this reason, the setting of the frequency jump band described above is manually performed by the user after installation of the mechanical system and construction work around it are completed. However, setting the frequency jump band is labor intensive and may pose a danger to the user depending on the type of mechanical system and the installation location.

Accordingly, the present invention provides a motor assembly that can automatically set a frequency jump band.

In one aspect, the electric motor assembly comprises an electric motor, an inverter supplying AC power to the electric motor, a vibration sensor fixed to the inverter, and determining a frequency jump band based on an output value of the vibration sensor. A frequency jump control unit is provided, and the inverter is fixed to the electric motor, and the electric motor includes a drive shaft, a rotor fixed to the drive shaft, and a stator arranged around the rotor. , a motor casing that accommodates the rotor and the stator, and the inverter includes an inverter substrate having an electric circuit, switching elements, and an inverter casing that accommodates the inverter substrate and the switching elements. , the vibration sensor is fixed to the inverter board, the inverter board is perpendicular to the drive shaft, the drive shaft extends through the inverter board, the motor casing and The inverter casings are arranged in series along the drive shaft, and the frequency jump control unit controls the lower limit value of the frequency jump band or A motor assembly is provided configured to cause the inverter to output AC power having a frequency corresponding to the upper limit.

In one aspect, the frequency jump band is a range of command frequencies to the inverter corresponding to output values of the vibration sensor greater than a threshold value.
In one aspect, the frequency jump control unit acquires the output value of the vibration sensor while changing the rotation speed of the electric motor, compares the output value of the vibration sensor with a threshold value, and is configured to determine a command frequency range corresponding to the output value of the vibration sensor having a larger value, and set the determined range as the frequency jump band .
In one aspect, at least part of the internal space of the inverter casing is filled with resin, and the inverter board and the vibration sensor are embedded in the resin .

According to the invention, the inverter is fixed to the electric motor and the vibration sensor is fixed to the inverter. Therefore, the vibration sensor can accurately detect the magnitude of vibration caused by the rotation of the electric motor. Further, according to the present invention, after a mechanical system incorporating a motor assembly (for example, a pump device such as a water supply device) is installed, the frequency jump band is automatically adjusted by combining the vibration sensor and the frequency jump control section. can be set.

1 is a cross-sectional view showing one embodiment of a motor assembly; FIG. FIG. 5 is a cross-sectional view showing another embodiment of the electric motor assembly; FIG. 4 is a graph illustrating one embodiment of a method for determining and setting frequency jump bands; FIG. FIG. 4 is a graph illustrating one embodiment of a method for determining and setting frequency jump bands; FIG. 7 is a graph illustrating frequency jumps when the command frequency is rising; 7 is a graph explaining frequency jumps when the command frequency is decreasing;

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a cross-sectional view showing one embodiment of an electric motor assembly. As shown in FIG. 1 , the motor assembly 1 includes a motor 2 and an inverter 3 that supplies AC power to the motor 2 . The inverter 3 is fixed to the electric motor 2, and the electric motor 2 and the inverter 3 form an integrated structure. A drive shaft 5 of the electric motor 2 extends through the inverter 3 .

The electric motor 2 includes a drive shaft 5 , a rotor 6 fixed to the drive shaft 5 , a stator 7 arranged around the rotor 6 , and a motor casing 10 housing the rotor 6 and the stator 7 . ing. The drive shaft 5 is rotatably supported by two bearings 27 , 28 fixed to the motor casing 10 . The inverter 3 is connected to the stator 7 by power lines (not shown). When the inverter 3 supplies AC power to the stator 7 , the stator 7 forms a rotating magnetic field around the rotor 6 . The rotor 6 is rotated by the rotating magnetic field, and the drive shaft 5 rotates together with the rotor 6 .

The inverter 3 includes an inverter board 42 having an electric circuit 41 , a capacitor 43 , switching elements 44 , and an inverter casing 21 housing the inverter board 42 and the switching elements 44 . Inverter casing 21 is fixed to motor casing 10 .

Drive shaft 5 extends through motor casing 10 and inverter casing 21 . Motor casing 10 and inverter casing 21 are arranged concentrically with drive shaft 5 . In this embodiment, since the motor casing 10 and the inverter casing 21 are arranged in series along the drive shaft 5, the electric motor assembly 1 can be made compact.

One end of the drive shaft 5 is connected to a rotating machine (for example, a pump) (not shown). A cooling fan 25 is fixed to the other end of the drive shaft 5 . The cooling fan 25 is arranged outside the inverter 3 and is adjacent to the end surface of the inverter 3 . When electric motor 2 rotates, cooling fan 25 rotates to form airflow on the outer surfaces of inverter casing 21 and motor casing 10 . The electric motor assembly 1 has a fan cover 51 that covers the cooling fan 25 . Fan cover 51 is fixed to inverter casing 21 .

In FIG. 1, the electric motor 2 is depicted schematically. The electric motor 2 is, for example, a permanent magnet type motor using a permanent magnet for the rotor 6 . However, the electric motor 2 is not limited to a permanent magnet type motor, and may be various types of motors such as an induction motor and an SR motor.

The inverter casing 21 has cooling fins 56 on its outer peripheral surface. The cooling fins 56 extend in the longitudinal direction of the drive shaft 5 . The inverter casing 21 further has cooling fins 36 on its end face. The cooling fins 36 are adjacent to the cooling fan 25 and radially extend from the drive shaft 5 . The motor casing 10 has cooling fins 57 on its outer peripheral surface. The cooling fins 57 extend in the longitudinal direction of the drive shaft 5 .

The air flow formed by cooling fan 25 flows over the outer surfaces of inverter 3 and electric motor 2 while contacting cooling fins 36 , 56 and 57 . Inverter 3 and electric motor 2 are cooled by this air flow. The switching element 44 is in contact with the inner surface of the inverter casing 21 and located behind the cooling fins 36 . With such an arrangement, the switching element 44 is efficiently cooled by the airflow created by the cooling fan 25 .

The inverter board 42 is fixed to the inner surface of the inverter casing 21 behind the cooling fins 36 . A drive shaft 5 of the electric motor 2 extends through the inverter board 42 . The inverter board 42 is perpendicular to the drive shaft 5 . The electric motor assembly 1 further includes a tubular wall 50 that covers the outer peripheral surface of the drive shaft 5 . This cylindrical wall 50 is arranged inside the inverter 3 . The inverter board 42 has an annular shape through which the drive shaft 5 and the tubular wall 50 penetrate, and is arranged concentrically with the drive shaft 5 . The cylindrical wall 50 can prevent the power line (not shown) connecting the inverter 3 and the stator 7 from contacting the drive shaft 5 .

The electric motor assembly 1 further includes a vibration sensor 60 fixed to the inverter 3 and a frequency jump control section 63 that determines the frequency jump band based on the output value of the vibration sensor 60 . In this embodiment, the vibration sensor 60 is fixed to the inverter board 42 . In one embodiment, vibration sensor 60 may be fixed to inverter casing 21 . This vibration sensor 60 is a vibration detector for measuring the magnitude of vibration generated due to rotation of the electric motor 2 . Since inverter 3 is fixed to electric motor 2 and vibration sensor 60 is fixed to inverter 3, vibration sensor 60 can accurately detect the magnitude of vibration.

In this embodiment, the vibration sensor 60 particularly detects resonance when the rotation speed of the electric motor 2 matches the natural frequency of a mechanical system (for example, a pump device such as a water supply device) in which the electric motor assembly 1 is incorporated. used to The direction of vibration when resonance occurs is perpendicular to the drive shaft 5 . Since the inverter board 42 is perpendicular to the drive shaft 5, the inverter board 42 is less likely to bend (or deform) when resonance occurs. Therefore, the vibration sensor 60 fixed to the inverter board 42 can accurately detect resonance.

As shown in FIG. 2, in order to prevent bending of the inverter board 42 and to efficiently transmit vibrations to the vibration sensor 60, at least a part of the internal space of the inverter casing 21 is filled with a resin 68, 42 and vibration sensor 60 may be embedded in resin 68 .

Returning to FIG. 1 , the frequency jump control section 63 is fixed to the inverter 3 . In this embodiment, the frequency jump controller 63 is arranged inside the inverter 3 . More specifically, the frequency jump controller 63 is mounted on the inverter board 42 . In one embodiment, frequency jump controller 63 may be separate from inverter board 42 . Furthermore, in one embodiment, the frequency jump controller 63 may be located outside the inverter 3 .

The frequency jump control unit 63 has a storage device 63a for storing programs and an arithmetic device 63b for executing calculations according to the programs. In this embodiment, the arithmetic device 63 b is provided independently of the inverter 3 , but the arithmetic device of the inverter 3 may function as the arithmetic device of the frequency jump control section 63 . The vibration sensor 60 is electrically connected to the frequency jump control section 63 , and the output value of the vibration sensor 60 is sent to the frequency jump control section 63 .

Frequency jump control unit 63 compares the output value of vibration sensor 60 with a threshold value, determines the range of command frequencies to inverter 3 corresponding to output values greater than the threshold value, and determines the command frequency range. is configured to set the frequency jump band. The frequency jump controller 63 stores the determined frequency jump band in the storage device 63a.

During operation of the motor assembly 1 , the frequency jump control section 63 is connected to a control device (not shown) arranged outside the motor assembly 1 . The control device is, for example, a control device for controlling the operation of a pump connected to the electric motor assembly 1 . A command frequency is input to the frequency jump control section 63 from this control device. The command frequency is a command value for the frequency of AC power that the inverter 3 should supply to the electric motor 2 . When the command frequency to the inverter 3 is outside the frequency jump band, the frequency jump control unit 63 causes the inverter 3 to output AC power having the same frequency as the command frequency, and the command frequency to the inverter 3 is within the frequency jump band. In some cases, the inverter 3 is configured to output AC power having a frequency corresponding to the lower limit or upper limit of the frequency jump band. Such a function is called a frequency jump function. In this specification, the frequency of the AC power output from the inverter 3 is called output frequency.

The frequency jump function is the same as the operation described with reference to FIGS. 5 and 6. FIG. That is, as shown in FIG. 5, when the command frequency rises and reaches the frequency jump band, the output frequency of the inverter 3 is fixed at the lower limit value L of the frequency jump band. While the rising command frequency is within the frequency jump band, the output frequency of the inverter 3 is maintained at the lower limit value L of the frequency jump band. When the command frequency exceeds the frequency jump band, the output frequency of inverter 3 returns to the same frequency as the command frequency.

As shown in FIG. 6, when the command frequency decreases and reaches the frequency jump band, the output frequency of the inverter 3 is fixed at the upper limit value H of the frequency jump band. While the decreasing command frequency is within the frequency jump band, the output frequency of the inverter 3 is maintained at the upper limit value H of the frequency jump band. When the command frequency falls below the frequency jump band, the output frequency of inverter 3 returns to the same frequency as the command frequency.

The natural frequency of a mechanical system (for example, a pump device such as a water supply system) in which the electric motor assembly 1 is incorporated can vary depending not only on the mechanical system itself but also on attachments such as piping fixed to the mechanical system. According to this embodiment, the combination of the vibration sensor 60 and the frequency jump control section 63 can automatically determine and set the frequency jump band after the mechanical system is installed. Therefore, resonance of the mechanical system including the electric motor assembly 1 is prevented.

Determining and setting the frequency jump band is performed during a test run prior to normal operation of the motor assembly 1 . As shown in FIG. 3 , in the test run, the frequency jump control unit 63 changes the command frequency to the inverter 3 from 0 to the maximum frequency (rated frequency) Fmax, and while changing the rotation speed of the electric motor 2, the vibration sensor 60 Get the output value of . In this embodiment, the frequency jump control unit 63 is configured to linearly change the command frequency to the inverter 3 from 0 to the maximum frequency Fmax, and linearly change the rotational speed of the electric motor 2 at a constant acceleration. ing. The frequency jump control unit 63 compares the acquired output value of the vibration sensor 60 with a threshold value, and determines ranges R1 and R2 of command frequencies corresponding to output values of the vibration sensor 60 larger than the threshold value. The ranges R1 and R2 thus obtained are set as the frequency jump band. The frequency jump controller 63 stores the frequency jump bands R1 and R2 in the storage device 63a. In the example shown in FIG. 3, two frequency jump bands R1 and R2 are set. The number of frequency jump bands that can be set in frequency jump control section 63 is predetermined.

During operation of the electric motor 2, if the command frequency input from the external control device to the frequency jump control section 63 is in one of the plurality of frequency jump bands R1 and R2, the frequency jump control section 63 , causes the inverter 3 to output AC power having a frequency corresponding to the lower limit or upper limit of the frequency jump band.

The natural frequency of the mechanical system in which the motor assembly 1 is installed may change due to changes in the state of the mechanical system. Therefore, the frequency jump control unit 63 is configured to record the output value of the vibration sensor 60 in the storage device 63a during normal operation, and set a new frequency jump band after normal operation. More specifically, the frequency jump control unit 63 reads the output value of the vibration sensor 60 from the storage device 63a, determines the command frequency range corresponding to the output value of the vibration sensor 60 larger than the threshold value, and determines set the specified range to the new frequency jump band. The frequency jump controller 63 stores the newly set frequency jump band in the storage device 63a.

As shown in FIG. 4, depending on the environment in which a rotating machine such as a pump is installed, the command frequency input from the external control device to the frequency jump control unit 63 during normal operation of the motor assembly 1 may be the maximum frequency. (Rated frequency) Fmax may not be reached. For example, the operating frequency of a pump coupled to the motor assembly 1 may be lower than the maximum frequency Fmax. In such a case, although the output value of the vibration sensor 60 exceeds the threshold value, the peak (maximum value) is not reached, so the frequency jump control section 63 may not be able to detect the vibration peak. Therefore, in such a case, the frequency jump control unit 63 determines the lower limit frequency F1, which is the command frequency when the output value of the vibration sensor 60 exceeds the threshold value, and the maximum frequency F2 during operation, A difference between the maximum frequency F2 and the lower limit frequency F1 is calculated, and a jump width twice the difference is determined, and a new frequency jump band R3 centered on the maximum frequency F2 is determined. The frequency jump control unit 63 stores the newly set frequency jump band R3 in the storage device 63a.

In one embodiment, frequency jump controller 63 may set a new frequency jump band during normal operation. More specifically, the frequency jump control unit 63 acquires the output value of the vibration sensor 60 during normal operation, compares the output value of the vibration sensor 60 with a threshold value, and determines that the vibration sensor 60 output value is greater than the threshold value. is determined, and the determined range is set as a new frequency jump band. The frequency jump controller 63 stores the newly set frequency jump band in the storage device 63a.

Furthermore, in one embodiment, as described with reference to FIG. 4, the frequency jump control unit 63 acquires the output value of the vibration sensor 60 during normal operation, and uses the output value of the vibration sensor 60 as the threshold value. A lower limit frequency F1 and a maximum frequency F2, which are command frequencies when the output value of the vibration sensor 60 exceeds the threshold value, are compared, and the difference between the maximum frequency F2 and the lower limit frequency F1 is calculated. A new frequency jump band R3 may be determined that is twice as wide as , and centered at the maximum frequency F2. The frequency jump control unit 63 stores the newly set frequency jump band R3 in the storage device 63a.

As a result of any change in the natural frequency of the mechanical system, resonance may occur during normal operation of the motor assembly 1, even though the frequency jump is functioning normally. Therefore, in order to ensure safe operation of the mechanical system, the frequency jump control unit 63 adds or subtracts a preset jump width to or from the current command frequency when the output value of the vibration sensor 60 exceeds the threshold value. , and the output frequency of the inverter 3 is changed instantaneously. More specifically, when the output value of the vibration sensor 60 exceeds the threshold while the command frequency is increasing, the frequency jump control section 63 adds the jump width to the current command frequency. When the output value of the vibration sensor 60 exceeds the threshold while the command frequency is decreasing, the frequency jump control section 63 subtracts the jump width from the current command frequency. Such an operation allows the output frequency of the inverter 3 to instantaneously jump over the natural frequency (resonant frequency) of the mechanical system. As a result, resonance can be prevented.

As described above, the frequency jump function can ensure safe operation of mechanical systems by avoiding frequency bands where resonance is expected. However, if resonance occurs even though the frequency jump band described above has already been set, it is presumed that some problem has occurred in the mechanical system.

Therefore, in the present embodiment, the frequency jump control unit 63 operates when the command frequency is within the frequency jump band and the inverter 3 outputs AC power having a frequency corresponding to the lower limit or upper limit of the frequency jump band. Alternatively, when the command frequency is outside the frequency jump band and the inverter 3 is outputting AC power with the command frequency, if the output value of the vibration sensor 60 exceeds the above threshold value, the operation of the electric motor 2 is stopped. configured to stop. Such an operation can avoid damage to the mechanical system in which the electric motor assembly 1 is incorporated.

The number of frequency jump bands depends on the number of natural frequencies of the mechanical system including the motor assembly 1 . Therefore, if too many frequency jump bands are set, it is presumed that some trouble has occurred in the mechanical system.

Therefore, in this embodiment, the frequency jump control unit 63 is configured to stop the operation of the electric motor 2 when the number of set frequency jump bands is larger than a predetermined number. Such action can avoid damage to the mechanical system.

Since the number of frequency jump bands depends on the number of natural frequencies of the mechanical system including the electric motor assembly 1, the ratio of all the frequency jump bands to the entire operating frequency range of the electric motor 2 is equal to or less than a predetermined ratio. become. Therefore, in one embodiment, when the ratio of the sum of all frequency jump bands to the operating frequency range of the electric motor 2 exceeds a predetermined ratio, the frequency jump control unit 63 stops the operation of the electric motor 2. It is configured. The operating frequency range of the electric motor 2 is from 0 to the maximum frequency (rated frequency) Fmax of the electric motor 2 . Such an operation can avoid damage to the mechanical system in which the electric motor assembly 1 is incorporated.

The above-described embodiments are described for the purpose of enabling a person having ordinary knowledge in the technical field to which the present invention belongs to implement the present invention. Various modifications of the above embodiments can be made by those skilled in the art, and the technical idea of the present invention can be applied to other embodiments. Accordingly, the present invention is not limited to the described embodiments, but is to be construed in its broadest scope in accordance with the technical spirit defined by the claims.

1 Electric Motor Assembly 2 Electric Motor 3 Inverter 5 Drive Shaft 6 Rotor 7 Stator 10 Motor Casing 21 Inverter Casing 25 Cooling Fans 27, 28 Bearing 36 Cooling Fin 41 Electric Circuit 42 Inverter Board 43 Capacitor 44 Switching Element 50 Cylindrical Wall 51 Fan Cover 56 Cooling fin 57 Cooling fin 60 Vibration sensor 63 Frequency jump controller 63a Storage device 63b Arithmetic device 68 Resin

Claims (7)

A motor assembly,
an electric motor;
an inverter that supplies AC power to the electric motor;
a vibration sensor fixed to the inverter;
a frequency jump control unit that determines a frequency jump band based on the output value of the vibration sensor;
The inverter is fixed to the electric motor,
The electric motor includes a drive shaft, a rotor fixed to the drive shaft, a stator arranged around the rotor, and a motor casing housing the rotor and the stator,
The inverter includes an inverter board having an electric circuit, switching elements, and an inverter casing housing the inverter board and the switching elements,
The vibration sensor is fixed to the inverter board,
the inverter board is perpendicular to the drive axis;
The drive shaft extends through the inverter board,
The motor casing and the inverter casing are arranged in series along the drive shaft,
The frequency jump control unit is configured to cause the inverter to output AC power having a frequency corresponding to a lower limit value or an upper limit value of the frequency jump band when the command frequency to the inverter is within the frequency jump band. motor assembly. 2. The motor assembly according to claim 1, wherein said frequency jump band is a range of command frequencies to said inverter corresponding to output values of said vibration sensor greater than a threshold value. The frequency jump control unit obtains an output value of the vibration sensor while changing the rotation speed of the electric motor, compares the output value of the vibration sensor with a threshold value, and detects vibrations larger than the threshold value. 3. The electric motor assembly according to claim 1 or 2, configured to determine a range of command frequencies corresponding to the sensor output value and set the determined range to the frequency jump band. At least part of the internal space of the inverter casing is filled with resin,
2. The electric motor assembly according to claim 1 , wherein said inverter board and said vibration sensor are embedded in said resin. The frequency jump control unit obtains an output value of the vibration sensor during normal operation of the electric motor assembly, and is a lower limit frequency that is a command frequency when the output value of the vibration sensor exceeds a threshold value; A maximum frequency during operation of the motor assembly is determined, a difference between the maximum frequency and the lower limit frequency is calculated, and a new jump width having a width twice the difference as a jump width and centering on the maximum frequency is determined. 5. A motor assembly as claimed in any one of the preceding claims, arranged to determine a frequency jump band. The frequency jump control unit obtains an output value of the vibration sensor during normal operation of the electric motor assembly, determines a command frequency range corresponding to the output value of the vibration sensor greater than a threshold value, and determines 5. A motor assembly as claimed in any one of claims 1 to 4, configured to set the selected range to a new frequency jump band. The frequency jump control unit adds a preset jump width to the current command frequency when the output value of the vibration sensor exceeds a threshold value while the command frequency is increasing, and the vibration is detected while the command frequency is decreasing. 7. A motor assembly as claimed in any one of the preceding claims, arranged to subtract the jump width from the current commanded frequency when the sensor output value exceeds a threshold value.

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