JP2001140766A - Driving device of pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driving device of pump capable of stably restarting a motor-again even if a bimetal type circuit breaker operates. SOLUTION: In this driving device of a pump equipped with a converter part 1 to convert AC to DC by connecting it to a commercial AC power source, an inverter part 2 to supply AC power to a motor 6 by inversely converting power to the AC power having an optional frequency and voltage from the power converted to DC, and a control part 4 to supply a control signal to the inverter part and to control operation of a pump connected to the motor, the output power to the motor is limited and the signal is outputted outside, when the current supplied to the motor 6 is smaller than a designated value.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a pump drive device capable of arbitrarily changing the operation speed of a pump by supplying AC power of an arbitrary frequency and voltage from a commercial AC power supply to a pump motor, and in particular, to controlling the drive device. The present invention relates to a mechanism for monitoring a load current to a motor of a section.

[0002]

2. Description of the Related Art FIG. 1 shows an example of a circuit configuration of a pump driving device that performs variable speed operation of a pump by supplying AC power of an arbitrary frequency and voltage from a commercial AC power supply to a pump motor. The diode module 1 is, for example, a commercial three-phase 2
It is a converter section for converting 00V AC power into DC power, and is a circuit in which a diode element is connected to a bridge circuit to perform full-wave rectification on a commercial AC power supply. The output side of the diode module 1 is connected to the smoothing capacitor 3, and smoothes the AC voltage that has been full-wave rectified by the diode module 1 into a DC voltage. The output side of the smoothing capacitor 3 is connected to the power module 2, and this power module 2 constitutes an inverter unit that reversely converts DC power into AC power of an arbitrary frequency and voltage.

In the power module 2, a power switching element such as a power transistor, a power MOS, or an IGBT is connected to, for example, a 6-arm bridge circuit, and the power switching element is switched by pulse width modulation (PWM) control or the like. Then, DC power is inversely converted into AC power of an arbitrary frequency and voltage. The output of the power module 2 is supplied to a pump motor 6 to drive the pump at a variable speed. The control circuit 4 is configured by a microcomputer or the like, and generates a pulse width modulation signal for the power module 2 to generate an AC output of an arbitrary frequency and voltage. Then, this signal is supplied by the drive circuit 5 to the gate and the like of the power switching element of the power module 2, and the switching is performed.

A sensor 7 for detecting a current is connected to an output circuit from the power module 2 to the pump motor 6, and an output of the sensor 7 is transmitted to a control circuit 4 via an arithmetic unit 3. When the detected current is an abnormal current exceeding the rated load current, the control unit 4 determines that the current is an overcurrent state and stops outputting the pulse width modulation signal. As a result, the supply of the output voltage from the power module 2 to the motor 7 is stopped, and the so-called overcurrent interrupter is tripped. The inrush current prevention circuit 8 is a circuit for preventing the inrush current from flowing through the capacitor when the power is turned on, and is a combination of a low resistance and a time switch for bypassing the low resistance.

[0005]

Incidentally, the pump motor 6 may have a built-in protection device which is a bimetal type current interrupting device 9 called an auto cut in the motor depending on the kind of the pump. As shown in FIG. 2, the bimetal-type current interrupting device is a safety device that, when the temperature rises, the metal piece 9a of the bimetal warps and opens the circuit contact. In such a case, if the temperature of the motor rises for some reason, the contact of the bimetal type current interrupter opens and interrupts the load current to the motor. As a result, the motor stops. Then, when the temperature inside the motor decreases after the motor stops, the bimetallic contact closes and automatically returns, and the motor resumes operation.

However, the current interruption operation by the bimetallic current interruption device and the resumption of the current application by the automatic return are performed inside the pump motor 6, and are independent of the operation of the drive device. Therefore, even if the bimetal-type current interrupter 9 is opened, the control circuit 4 keeps the power module 2
Output of the pulse width modulation signal is continued. For this reason,
When the bimetal-type current interrupter 9 automatically returns, an inrush current flows to the stopped motor, so that the overcurrent protection function of the control circuit 4 operates to stop the output of the power module 2. is there. That is, even if the bimetal type current interrupter operates, the supply of the voltage from the power module 2 to the motor side is still output, so that when the stopped motor is restarted, the motor restarts due to the rush current. Can not be done.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a pump driving device capable of restarting the operation of a motor stably even when a bimetallic current interrupter operates.

[0008]

According to a first aspect of the present invention, there is provided a converter section for connecting an AC power supply to a commercial AC power supply and converting the AC power to DC power,
A pump comprising: an inverter for converting the voltage into AC power and supplying the AC power to the motor; and a control unit for supplying a control signal to the inverter and controlling operation of a pump connected to the motor. A drive device for a pump, wherein when a current supplied to the motor is smaller than a predetermined value, an output to the motor is limited and a signal is output to the outside.

According to a second aspect of the present invention, the motor is provided with a bimetal type current interrupter, and when the interrupter is opened, it is detected that the current supplied to the motor is almost zero. Thus, the output of the inverter unit is limited to a low level.

According to a third aspect of the present invention, the motor includes a bimetal type current interrupter, and when the interrupter is closed, the voltage supplied to the motor is gradually increased by soft start. It is characterized by the following.

As a result, when the current is cut off by operating the bimetal type current cutoff device, the current flowing to the motor becomes almost zero, and by detecting this, the output of the power module 2 is reduced to a low frequency / voltage. Restrict to values. Therefore, when the bimetal type current interrupter automatically returns due to a decrease in the temperature of the motor, the magnitude of the inrush current is significantly limited even when the motor is stopped. Therefore, the overcurrent protection works and the trip state is prevented. When the current falls below a predetermined value, the state is output as a signal to the outside, whereby the abnormal state can be transmitted to the outside as an alarm. Then, by starting the pump by, for example, soft start, it is possible to take measures to enable smooth restart of operation.

[0012]

Embodiments of the present invention will be described below with reference to FIGS.

The pump driving apparatus according to the embodiment of the present invention has the same hardware configuration as that shown in FIG.
That is, the three-phase commercial AC power supply is rectified and smoothed by the converter unit 1, a DC power supply is constituted by the smoothing capacitor 3, and the DC power supply 2 converts the DC power supply to an arbitrary frequency
The basic configuration of constituting a voltage AC power supply and supplying it to the pump motor 6 is the same as the apparatus shown in FIG. A control circuit 4 comprising a microcomputer or the like is provided, thereby forming a pulse width modulation signal, and by switching a power switching element of the power module 2 via a drive circuit 5, an arbitrary frequency and voltage can be controlled. The configuration for forming the AC power supply is the same as described above.

Further, a current sensor 7 is provided in the output circuit of the motor, and this output is compared with a reference value by the arithmetic unit 3, and the output is transmitted to the control circuit 4 to perform various protection operations. The same is true for Similarly, an external output terminal 10 is provided, and various alarms and the like are output to the outside of the monitoring room or the like by opening and closing various contacts. Note that the current sensor 7 may be provided in a DC power supply unit upstream of the power module 2.

If, for example, CT is used as the current sensor 7, the arithmetic unit 3 converts an AC current signal into an AC voltage signal,
Further, this signal is detected, for example, converted into a DC voltage signal, and compared with a set value. The control circuit 4 of the present invention has the following functions. That is, when the detected value is smaller than the set value, it is determined that the bimetallic current interrupter has been opened, and the control circuit 4 determines that the power module 2
Limit the signal output to That is, the AC frequency and voltage output from the power module 2 are reduced to low values. Here, the set value is set to a value lower than the current value in the no-load operation state of the pump, not detected during normal operation, and only when the current when the bimetal type current interrupter is open is almost zero. To be detected. Thereby, it is possible to prevent the low current state at the time of soft start from being erroneously determined as the state in which the bimetal type current interrupter is opened. At the same time, the signal is transmitted to the external signal output circuit 10, and the contact of the external signal output terminal is opened and closed.

In addition, in preparation for the automatic recovery of the bimetal type current interrupter 9 after that state, if there is a current equal to or higher than a predetermined level so that a low-level inrush current at that time can be detected, it is determined that automatic recovery is performed. Then, the output frequency and voltage of the power module 2 are returned to the steady state. In this manner, during steady operation, it is detected that the output current to the motor is equal to or less than the predetermined value, and a signal indicating abnormally low current is output to the outside. This makes it possible to take a measure corresponding to the automatic return of the bimetal type current interrupter, and to prevent tripping due to overcurrent protection during automatic return.
Therefore, smooth operation return of the pump stopped by the bimetallic current interrupter 9 is possible.

FIG. 3 shows a typical example of driving a motor by a driving device for a variable frequency / voltage pump. The horizontal axis is time, and the vertical axis is output frequency. When the power is turned on, the control circuit 4 performs a soft start in which the power module 2 gradually increases the output frequency and voltage from zero. That is,
Predetermined speed the rotational speed of the motor from zero during the time T _1,
For example, increase to the rated speed. This avoids the problem of inrush current when starting the motor by directly applying the rated frequency and voltage to the stopped motor,
The motor can be smoothly raised to a predetermined rotation speed. Then, enter the steady-state operation the output frequency and voltage is a constant value, during the time T _2, to continue this state. Then, the control circuit 4 by a power-off reduces the gently output frequency and voltage to stop the operation speed in a steady state during a predetermined time T _3. As a result, the pump motor enters a soft stop state, and the speed gradually decreases to a stop.

FIG. 4 shows an operation example of the driving device for the pump according to the embodiment of the present invention. Here, during the steady operation time T _2, the bimetallic current interrupting device 9 by the temperature rise of the pump motor 6 at time t ₁ is the current flowing in operation to the motor 6 is cut off, the current sensor 7 This Detect the condition,
It is compared with a reference value calculator 3 determines that electric current to the motor 6 is equal to or less than the predetermined value I _0. Then, the output is transmitted to the control circuit 4 and the signal is transmitted to the external output circuit 10. An alarm signal is output from the external output circuit 10, and a signal indicating abnormality is transmitted to a monitoring room or the like. On the other hand, the control circuit 4 immediately stops outputting the steady-state frequency and voltage of the power module 2. Instead, the output in a state where the frequency and the voltage are greatly reduced with respect to the output in the steady state is continued. At this time, since the circuit is opened by the bimetal type current interrupter 9 and no current flows through the motor, the motor enters a free-run state and stops.

In the monitoring room, by receiving an alarm,
You can rush to the spot and take necessary measures. Further, even when the administrator cannot go to the site, the automatic return of the bimetal type current interrupt device can be safely performed as follows.

At time t ₂ , the motor 6 is sufficiently cooled and the bimetal is closed, and the bimetal current interrupter 9
Is closed. At this time, since a small frequency and voltage are output from the power module 2 side, an inrush current flows to the motor 6 although the value is small when the bimetal type current interrupting device 9 returns to the reset state. Current sensor 7
Detects this current, and the arithmetic unit 3 detects the automatic return of the bimetal type current interrupter 9. As a result, the control circuit 4 activates a soft start for gradually increasing the frequency and voltage to a steady state. Thereby, the motor 6 returns to the steady state operation again.

[0021] Incidentally, the arithmetic unit 3, only the time T ₁ during soft-start, may be processed so as not to determine the current level has been detected. Thus, the output current during soft-start is detected to be at I ₀ or less, the problem of lowering is prevented incorrectly output level of the power module 2. In addition, the current sensor and the arithmetic unit can use the existing overcurrent protection circuit and the like, and provide a safe and reliable pump driving device without almost any additional cost. Can be.

In the above-described embodiment, the motor output current is reduced by the bimetal type current interrupter by the current sensor provided in the output circuit of the motor. You may make it detect and operate.

[0023]

As described above, according to the present invention, even in a motor pump having a bimetallic current interrupter or the like, a trip or the like due to an inrush current does not occur when the bimetallic current interrupter automatically returns. The operation of the pump can be stably performed.

[Brief description of the drawings]

FIG. 1 is a block diagram of a driving device of a pump.

FIG. 2 is a diagram showing a bimetal type current interrupt device.

FIG. 3 is a diagram showing an operation pattern of the pump, in which the horizontal axis represents time and the vertical axis represents output frequency / voltage.

4A and 4B are diagrams showing an operation pattern of the pump according to the embodiment of the present invention, wherein FIG. 4A shows the output frequency and voltage of the power module, FIG. 4B shows the output current of the motor, Time.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Diode module (converter part) 2 Power module (inverter part) 3 Smoothing capacitor 4 Control part 5 Drive circuit 6 Pump motor 7 Current sensor 8 Inrush current prevention circuit 9 Bimetal type current breaker 10 External output circuit

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hideki Ogino 4-1-1 Motofujisawa, Fujisawa-shi, Kanagawa Prefecture Ebara Densan Co., Ltd. (72) Koji Hirasawa 4-1-1 Motofujisawa, Fujisawa-shi, Kanagawa No. 1 F-term in EBARA Densan Co., Ltd. (Reference) 3H045 AA09 BA03 BA07 BA31 BA41 CA21 CA24 DA01 DA02 DA07 DA45 EA16 EA20 EA26 EA34 EA49 5H007 AA05 BB06 DA05 DB02 DC02 DC05 FA03 GA02 GA03 5H576 AA05 CC01 DD02 DD04 GG04 FF HB01 KK01 LL22 LL24 MM02

Claims (3)

[Claims] A converter for connecting an AC power supply to a commercial AC power supply and converting the DC power into an AC power having an arbitrary frequency and voltage, and supplying the AC power to the motor; In a pump driving apparatus, comprising: an inverter unit, and a control unit that supplies a control signal to the inverter unit and controls an operation of a pump connected to the motor, when a current supplied to the motor is smaller than a predetermined value. ,
A pump driving device wherein output to the motor is restricted and a signal is output to the outside. 2. The motor according to claim 1, wherein said motor is provided with a bimetal-type current interrupter, and when the interrupter is opened, it is detected that the current supplied to the motor is almost zero. 2. The driving device for a pump according to claim 1, wherein the driving force is restricted to a low level. 3. The motor according to claim 1, wherein the motor includes a bimetallic current interrupter, and when the interrupter is closed, the voltage supplied to the motor is gradually increased by a soft start. 3. The pump driving device according to 2.