JP2014231823A - Pump device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a pump device capable of smoothly starting a freely rotating motor without deceleration, and preventing application of an induced voltage of the motor to an inverter.SOLUTION: A pump device includes a pump P, a motor M connected to the pump P, an inverter 10 driving the motor M, a motor state detecting portion 50 detecting a rotating speed of the freely rotating motor M from an induced voltage generated on the motor M, a pump control portion 60 creating a speed command value of the motor M to minimize the difference between a discharge pressure of the pump P and a prescribed target pressure, and an inverter control portion 16 calculating a voltage command value necessary for the motor M to rotate under the speed command value. The pump control portion 60 uses the rotating speed of the motor M detected by the motor state detecting portion 50 as an initial value of the speed command value.

Description

  The present invention relates to a pump device for transferring a liquid.

  Permanent magnet synchronous motors are widely used as motors for driving pumps because they are highly efficient and maintenance-free. In a water supply apparatus that supplies water to a building, a motor is controlled by a pump control unit via an inverter so that a discharge pressure of the pump is maintained at a predetermined target pressure. More specifically, the pump control unit calculates a speed command value for minimizing the difference between the current discharge pressure and the target pressure, and sends this to the inverter control unit. The inverter control unit calculates a voltage command value necessary for the motor to rotate at the speed command value, and transmits the voltage command value to the inverter. Further, the inverter applies a voltage corresponding to the voltage command value to the motor, thereby rotating the motor so that the discharge pressure of the pump is maintained at a predetermined target pressure.

When starting the motor, 0 [min ⁻¹ or Hz or ω] is normally input to the inverter control unit as the initial value of the speed command value. The motor gradually increases from the stopped state as the speed command value increases. However, the situation of starting the motor includes not only the case of starting the motor in a stopped state but also the case of starting the motor that is freely rotated by inertia or external energy. For example, even when no electric power is supplied to the motor, the impeller may rotate the motor as a water wheel by the liquid flowing in the pump. Free rotation of the motor also occurs immediately after a momentary power failure. That is, when a momentary power failure occurs while the motor is being driven by the inverter, the motor continues to rotate for a while due to inertia even if no power is supplied to the motor.

  When the speed command value 0 is input to the inverter control unit while the motor is freely rotating, the motor is once decelerated and then accelerated toward the target pressure. Furthermore, when the output voltage of the inverter is lower than the induced voltage of the motor, the induced voltage of the motor is applied to the inverter, and in the worst case, the capacitor built in the inverter may be destroyed.

International Publication WO2012 / 133878 JP 2004-159500 A JP 2005-137106 A JP 2011-019348 A

  The present invention has been made in order to solve the above-described problems, and can smoothly start a freely rotating motor without decelerating, and the induced voltage of the motor is applied to the inverter. An object of the present invention is to provide a pump device that can be prevented.

In order to achieve the above-described object, one aspect of the present invention provides a pump, a motor connected to the pump, an inverter that drives the motor, and the motor that freely rotates from an induced voltage generated in the motor. A motor state detection unit that detects the rotation speed of the pump, a pump control unit that generates a speed command value of the motor for minimizing a difference between a discharge pressure of the pump and a predetermined target pressure, and the motor An inverter control unit that calculates a voltage command value required to rotate at a speed command value and transmits the voltage command value to the inverter, wherein the pump control unit is detected by the motor state detection unit The pump device is characterized in that the rotational speed of the motor is used as an initial value of the speed command value.
In a preferred aspect of the present invention, the motor state detection unit further detects a rotation direction of the motor that freely rotates from an induced voltage generated from the motor.

  According to the present invention, the motor is gradually accelerated from the current rotational speed of free rotation. Therefore, it is possible to prevent the motor from decelerating once and the induced voltage of the motor from being applied to the inverter.

It is a schematic diagram which shows one Embodiment of the pump apparatus of this invention. It is a figure which shows a three-phase voltage when a pump and a motor are freely rotating in the positive direction. It is a figure which shows a three-phase voltage when a pump and a motor are freely rotating in the reverse direction. It is a block diagram which shows an example of a motor state detection part. It is a figure which shows the flowchart which calculates the rotational speed (angular frequency) of the motor which is rotating freely. It is a figure which shows the phase of a pulse edge. It is a block diagram which shows the detail of the inverter shown in FIG. It is a block diagram of an inverter control part.

Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 is a schematic view showing an embodiment of the pump device of the present invention. As shown in FIG. 1, the pump device includes a pump P connected to a pipe 3 through which a liquid flows, a motor M connected to the pump P, and a variable frequency voltage applied to the motor M so that the motor M The inverter 10 to drive and the voltage measuring device 21 which measures the voltage applied to the motor M from the inverter 10 are provided. The inverter 10 is connected to an AC power source 1 such as a commercial power source. The pump P includes an impeller (not shown), and the liquid in the pipe 3 is transferred in the direction indicated by the arrow by the impeller rotated by the motor M.

  The pump device further includes an inverter control unit 16 that controls the inverter 10, a pump control unit 60 that transmits a speed command value of the motor M to the inverter control unit 16, and a pressure sensor (pressure) that measures the discharge pressure of the pump P Measuring instrument) 4. The pressure sensor 4 is attached to the pipe 3. The pressure sensor 4 is connected to the pump control unit 60, and the discharge pressure measurement value is sent to the pump control unit 60.

  The pump control unit 60 calculates a difference between the measured value of the discharge pressure and a preset target pressure, and calculates a speed command value of the motor M for minimizing this difference. The inverter control unit 16 receives the speed command value from the pump control unit 60, and generates a voltage command value necessary for the motor M to rotate at this speed command value. The inverter 10 receives this voltage command value, generates a voltage indicated by this voltage command value, and applies it to the motor M. In this way, the motor M rotates the pump P to achieve the target pressure.

  When the liquid flows in the pipe 3 while the motor M is stopped, the pump P is rotated by the flow of the liquid, and the motor M connected to the pump P is also rotated. Further, if a momentary power failure occurs while the motor M is being driven by the inverter 10, even if no power is supplied to the motor M, the rotor of the motor M continues to rotate for a while due to inertia. In this specification, the state in which the motor M is rotated by external kinetic energy or inertia without being supplied with electric power is referred to as “free rotation”.

  The freely rotating motor M generates an induced voltage. The induced voltage generated in the motor M is measured by the voltage measuring device 21. The pump device further includes a motor state detection unit 50 that determines the rotation speed and rotation direction of the motor M from the induced voltage of the motor M. This motor state detection unit 50 detects the rotational speed of the motor M that is freely rotating from the three-phase voltage induced in the motor M, that is, the phase change of the U-phase voltage, the V-phase voltage, and the W-phase voltage. Further, the rotational direction of the motor M is detected from the phase order of the U-phase voltage, the V-phase voltage, and the W-phase voltage.

  FIG. 2 is a diagram showing a three-phase voltage when the pump P and the motor M are freely rotating in the forward direction, and FIG. 3 is a three-phase voltage when the pump P and the motor M are freely rotating in the opposite direction. FIG. As shown in FIG. 2, when the pump P rotates in the positive direction, the U-phase voltage, the V-phase voltage, and the W-phase voltage are generated with a phase difference of 120 degrees in this order. When the pump P rotates in the reverse direction due to the reverse flow of the liquid, as shown in FIG. 3, the U-phase voltage, the W-phase voltage, and the V-phase voltage are generated in this order with a phase difference of 120 degrees. Thus, the phase order of the induced voltage of the motor M differs depending on the rotation direction of the pump P, that is, the rotation direction of the motor M. The motor state detection unit 50 determines the rotation direction of the motor M from the phase sequence of the induced voltage of the motor M.

FIG. 4 is a block diagram illustrating an example of the motor state detection unit 50. Motor state detecting section 50, a first voltage comparator 51A for generating a first pulse signal P _UV according to the difference between the V-phase voltage and the U-phase voltage, according to the difference between the W-phase voltage and the V-phase voltage A second voltage comparator 51B that generates a second pulse signal P _VW , a first pulse edge detector 52A that detects a pulse edge of the first pulse signal P _UV , and a second pulse signal P _VW The rotation speed and direction of rotation of the motor M from the second pulse edge detection unit 52B for detecting the pulse edge, the time change and the order of the pulse edge of the first pulse signal P _{UV and} the pulse edge of the second pulse signal P _VW And a state determining unit 55 for determining

The first voltage comparator 51A compares the U-phase voltage and the V-phase voltage to generate a pulse signal _PUV as shown in FIGS. Specifically, a high-level signal is generated when the V-phase voltage is higher than the U-phase voltage, and a low-level signal is generated when the V-phase voltage is lower than the U-phase voltage. Similarly, the second voltage comparator 51B compares the V-phase voltage and the W-phase voltage to generate the pulse signal _PVW . That is, a high-level signal is generated when the W-phase voltage is higher than the V-phase voltage, and a low-level signal is generated when the W-phase voltage is lower than the V-phase voltage.

As can be seen from FIGS. 2 and 3, the pulse signal P _UV rising edge E1 and the falling edge E2 is manifested in that the voltage of the U-phase voltage and the V-phase crossing, a rising edge of the pulse signal P _VW E3 The falling edge E4 appears at the point where the V-phase voltage and the W-phase voltage intersect.

The pulse signal P _UV and the pulse signal P _VW generated by the voltage comparators 51A and 51B are sent to the first pulse edge detector 52A and the second pulse edge detector 52B, respectively. First pulse edge detection unit 52A, each time detects the pulse signal P _UV rising edge E1 and the falling edge E2, these rising edges E1 and falling edge E2 is detected, the state determines the pulse edge detection signal Send to part 55. Similarly, the second pulse edge detector 52B detects the rising edge E3 and the falling edge E4 of the pulse signal _PVW , and each time the rising edge E3 and the falling edge E4 are detected, the pulse edge detection signal Is sent to the state determination unit 55. Hereinafter, the rising edge and falling edge of the pulse signal P _UV and the pulse signal P _VW are collectively referred to as a pulse edge. 2 and 3, it can be seen that four pulse edges E1, E2, E3, and E4 appear within one cycle of the induced voltage of the motor M. FIG.

From FIG. 2, it can be seen that when the motor M rotates in the positive direction, four pulse edges E3, E2, E4, and E1 appear in this order within one cycle of the induced voltage of the motor M. In contrast, when the motor M rotates in the reverse direction, it can be seen from FIG. 3 that four pulse edges E1, E4, E2, and E3 appear in this order within one cycle of the induced voltage of the motor M. . Therefore, the state determination unit 55 can determine the rotation direction of the motor M from the order in which the pulse edges of the pulse signals P _UV and P _VW appear. That is, when the pulse edges E3, E2, E4, and E1 appear in this order, the state determination unit 55 outputs a rotation direction signal indicating that the motor M is rotating in the positive direction, and the pulse edges E1, E4 , E2, and E3 appear in this order, a rotation direction signal indicating that the motor M is rotating in the reverse direction is output. The rotation direction signal is sent to the pump control unit 60.

  As described above, the state determination unit 55 determines the rotation direction of the motor M from the order of the pulse edges. Further, upon receiving the pulse edge detection signal from the first pulse edge detection unit 52A or the second pulse edge detection unit 52B, the state determination unit 55 specifies the phase of the motor M and the angle as described below. Start calculating the frequency (ie, the scalar quantity of the rotational speed).

FIG. 5 is a diagram showing a flowchart for calculating the rotational speed (angular frequency) of the motor M that is freely rotating. When receiving the pulse edge detection signal, the state determination unit 55 acquires the current time t _n . Next, the state determination unit 55 identifies the phase (angle) theta _n of the detected pulse edge, and sends the phase theta _n of the motor M at time t _n to the inverter control unit 16. The phase θ _n is set in advance for each pulse edge that appears within one cycle of the induced voltage. That is, as shown in FIG. 6, the phase of the pulse edge E1 is 5 / 6π, the phase of the pulse edge E2 is −1 / 6π, the phase of the pulse edge E3 is −1 / 2π, and the phase of the pulse edge E4 is 1 / 2π. Is set to

このようにして、モータ状態検出部５０は、自由回転しているモータＭの位相θ_ｎ、回転速度ω_ｎ、および回転方向を決定する。したがって、モータ状態検出部５０は、自由回転するモータＭの誘導電圧からモータＭの速度を検出する速度検出部として機能する。このようにして検出されたモータＭの回転速度および回転方向はポンプ制御部６０に送られ、モータＭの位相はインバータ制御部１６に送られる。 As shown in FIG. 5, the state determination unit 55 detects the current phase θ _n after detecting the current phase θ _n , the phase θ _n−1 when the previous pulse edge was detected, and the previous pulse edge. From the elapsed time Δt (= t _n −t _n−1 ) until the rotation, the rotational speed ω _n of the freely rotating motor M is determined as follows.

In this way, the motor state detection unit 50 determines the phase θ _n , the rotation speed ω _n , and the rotation direction of the freely rotating motor M. Therefore, the motor state detection unit 50 functions as a speed detection unit that detects the speed of the motor M from the induced voltage of the freely rotating motor M. The rotation speed and direction of the motor M detected in this way are sent to the pump control unit 60, and the phase of the motor M is sent to the inverter control unit 16.

  The pump control unit 60 compares the measured value of the discharge pressure sent from the pressure sensor 4 with a predetermined target pressure stored in the pump control unit 60, and compares the measured value of the discharge pressure with the target pressure. A speed command value for minimizing the difference is calculated, and the speed command value is transmitted to the inverter control unit 16. When starting the motor M, the rotational speed detected by the motor state detection unit 50 is used as an initial value of the speed command value. This initial value varies depending on the state of the motor M when the motor M is started. That is, the initial value is 0 when the motor M is stopped, and the initial value is a value other than 0 when the motor M is freely rotating.

  Thus, by using the rotation speed detected by the motor state detection unit 50 as the initial value of the speed command value, the pump control unit 60 can determine the optimum speed command based on the rotation speed of the freely rotating motor M. The value can be determined. Therefore, the motor M can smoothly increase the speed from the current rotational speed that is freely rotating.

  If the motor M is rotating in the reverse direction when the motor M is started, the motor M is started in the reverse rotation, and then the motor M is gradually accelerated in the forward direction. This is because when a rotating magnetic field that rotates in the forward direction is generated in the reversely rotating motor M, a reverse-phase voltage is applied to the motor M, and the motor M steps out and an overcurrent flows through the inverter 10. It is because it may end up. In the present embodiment, as described above, since the rotation direction of the freely rotating motor M is detected, an overcurrent to the inverter 10 when the motor M is rotating in the reverse direction can be prevented. Furthermore, it is possible to use any type of motor, a motor having a clockwise direction as a positive direction and a motor having a counterclockwise direction as a positive direction.

  FIG. 7 is a block diagram showing details of the inverter 10 shown in FIG. As shown in FIG. 7, the inverter 10 includes a converter circuit 11, an inverter circuit 12, and a gate drive circuit 13. The converter circuit 11 has a rectifier circuit, and is configured to convert three-phase AC power supplied from the AC power source 1 into DC power. The inverter circuit 12 includes a switching element such as an IGBT (insulated gate bipolar transistor), and generates three-phase AC power from the DC power converted by the converter circuit 11. The gate drive circuit 13 generates a gate drive signal for opening and closing each switching element of the inverter circuit 12. The switching element of the inverter circuit 12 is driven in accordance with a gate drive signal from the gate drive circuit 13, and the inverter circuit 12 thereby outputs AC power having a variable frequency.

  The current measuring device 20 measures the three-phase current output from the inverter circuit 12 and sends a measured value (output current signal) of the three-phase current to the inverter control unit 16. The inverter control unit 16 controls the rotational speed of the motor M based on the measurement value sent from the current measuring device 20 and the speed command value sent from the pump control unit 60. That is, the inverter control unit 16 receives the speed command value from the pump control unit 60 and generates a PWM signal based on the measurement signal from the current measuring device 20. This PWM signal is sent to the gate drive circuit 13. The gate drive circuit 13 generates a gate drive signal for driving the switching element of the inverter circuit 12 based on the PWM signal. The switching element of the inverter circuit 12 is driven in accordance with a gate drive signal from the gate drive circuit 13, and the inverter circuit 12 thereby outputs AC power having a variable frequency.

  FIG. 8 is a block diagram of the inverter control unit 16. The inverter control unit 16 is a vector control unit that decomposes the current supplied to the motor M into a torque current component and a magnetizing current component and independently controls them.

  The three-phase output current of the inverter 10 is measured by the current measuring device 20. The measured three-phase currents Iu, Iv, and Iw are converted into two-phase currents Id and Iq on the rotating coordinate system by the 3 / 2-phase converting unit 32 and the stationary / rotating coordinate converting unit 33, and then the magnetization voltage control is performed. Is input to the unit 34 and the torque voltage control unit 35. The magnetization voltage control unit 34 obtains a magnetization voltage command value Vd * that minimizes the deviation between the magnetization current Id and the magnetization current command value Id * by PI calculation. The magnetizing current command value Id * is an ideal magnetizing current calculated using the motor M model. The torque voltage control unit 35 obtains a torque voltage command value Vq * that minimizes the deviation between the torque current Iq and the torque current command value Iq * by PI calculation.

  The target torque current determination unit 37 determines a torque current command value Iq * for minimizing a deviation between the speed command value ω * input from the pump control unit 60 and the current speed ω. The current rotational speed ω is obtained by an axis error estimator (PLL) 38 based on the voltage command values Vd * and Vq *. Furthermore, the phase θ is obtained from the rotational speed ω by the integrator 39. The obtained phase θ is sent to the stationary / rotational coordinate converter 33 and the rotational / static coordinate converter 40. The voltage command values Vd * and Vq * are converted into three-phase voltage command values Vu *, Vv * and Vw * on the fixed coordinate system via the rotation / stationary coordinate conversion unit 40 and the 2/3 phase conversion unit 41.

  The inverter control unit 16 generates a PWM signal corresponding to these three-phase voltage command values Vu *, Vv *, and Vw *, and sends this PWM signal to the gate drive circuit 13. The gate drive circuit 13 generates a gate drive circuit PWM signal based on the PWM signal corresponding to the three-phase voltage command values Vu *, Vv *, Vw *, and the switching element operates based on the gate drive circuit PWM signal ( On, off). Thus, the inverter 10 generates a voltage based on the three-phase voltage command value from the inverter control unit 16 and applies it to the motor M.

When the motor M is started in a state where the motor M is freely rotating, the phase θ _{n of the} motor M is input from the motor state detection unit 50 to the integrator 39. As described above, the phase of the pulse edge E1 is set to 5 / 6π, the phase of the pulse edge E2 is set to −1 / 6π, the phase of the pulse edge E3 is set to −1 / 2π, and the phase of the pulse edge E4 is set to 1 / 2π. Yes. Therefore, if the pulse edge detected by the state determination unit 55 is the pulse edge E1, the state determination unit 55 sends 5 / 6π to the integrator 39 as the phase θ _n of the motor M. Similarly, if the detected pulse edge at the pulse edge E2, the state determination unit 55 sends a -1 / 6? As the phase theta _n of the motor M to the integrator 39. If the detected pulse edge is a pulse edge E3, the state determination unit 55 sends a -1 / 2 [pi to the integrator 39 as the phase theta _n of the motor M. If the detected pulse edge is a pulse edge E4, the state determination unit 55 sends the 1/2 [pi to the integrator 39 as the phase theta _n of the motor M.

When the phase theta _n is input, the integrator 39 resets the phase theta phase theta _n (replacing the phase theta phase theta _n), the phase theta _n stationary / rotating coordinate conversion section 33 and a rotating / stationary coordinate converter Send to part 40. As described above, since the vector control is started based on the phase θ _n of the freely rotating motor M, the inverter control unit 16 can start the motor M while preventing the motor M from stepping out.

  The inverter control unit 16 in the present embodiment is configured to control the inverter by a vector control method, but the present invention is not limited to this example, and the inverter control unit 16 controls the inverter by a V / f control method. It may be configured to.

  The embodiment described above is described for the purpose of enabling the person having ordinary knowledge in the technical field to which the present invention belongs to implement the present invention. Various modifications of the above embodiment can be naturally 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 the widest scope according to the technical idea defined by the claims.

DESCRIPTION OF SYMBOLS 1 AC power supply 3 Piping 4 Pressure sensor 10 Inverter 11 Converter circuit 12 Inverter circuit 13 Gate drive part 16 Inverter control part 20 Current measurement part 21 Voltage measurement part 50 Motor state detection part 51A, 51B Voltage comparator 52A, 52B Pulse edge detection part 55 State determination unit 60 Pump control unit P Pump M Motor

Claims (2)

A pump,
A motor coupled to the pump;
An inverter for driving the motor;
A motor state detector that detects the rotational speed of the motor that freely rotates from the induced voltage generated in the motor;
A pump controller for generating a speed command value of the motor for minimizing a difference between a discharge pressure of the pump and a predetermined target pressure;
An inverter control unit that calculates a voltage command value necessary for the motor to rotate at the speed command value, and transmits the voltage command value to the inverter;
The pump device, wherein the pump control unit uses the rotation speed of the motor detected by the motor state detection unit as an initial value of the speed command value.   The pump device according to claim 1, wherein the motor state detection unit further detects a rotation direction of the motor that freely rotates from an induced voltage generated from the motor.

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