JPS60125789A - Control circuit for driving hydraulic machine - Google Patents

Abstract

PURPOSE:To minimize fluctuation of hydraulic pressure upon increasing and decreasing the number of operating set of hydraulic machine by a method wherein the circuit, controlling the number of set of the hydraulic machine, operated under a constant speed, in accordance with the flow amount of fluid requested by a load side as well as the speed of the hydraulic machine capable of being operated under variable speed operation, is formed. CONSTITUTION:In case the output voltage and output frequency of an inverter 10 is increased to the same values as those of a commercial electric source 1 when a pump 16 is delivering 60% of the flow amount and the pumps 26, 36 are being stopped, the pump 16 is operated under the maximum speed and the amount of delivery becomes 100%. When the synchronizing condition of both commercial electric source 1 and the inverter 10 is detected by a cynchronizing detecting circuit 9, a switching breaker 13 is operated so that both of them are connected in parallel and the contact between the inverter 10 and a motor 15 is cut off immediately thereafter, the motor 15 is switched into the commercial electric source 1 without cutting of the electric source. Next, when the inverter 10 and the motor 25 are connected after the output frequency of the inverter 10 is minimized and, subsequently, the speed thereof is controlled so that the delivery of the pump 26 becomes 10%, 110% of the flow amount is obtained and the change of flow amount is smooth while the fluctuation of the pressure may be eliminated absolutely.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] This invention minimizes fluid pressure fluctuations that occur when changing the number of fluid machines in operation in order to change the flow rate of fluid sent out by a plurality of fluid machines. The present invention relates to a fluid mechanical drive control circuit.

[Prior art and its problems]

Fluid machines For example, when a pump pumps out water, if you want to adjust the amount of water sent out, you can adjust the opening of a valve installed in the pipe, but it is more energy efficient to change the rotation speed of the pump. It is also effective and preferable. Therefore, when it is desired to significantly change the flow rate of water, multiple pumps are installed and the number of pumps in operation and the pump speed during operation are controlled to obtain the required amount of water. By the way, since the pump is generally driven by connecting an induction motor to a commercial power source, a VVVF motor is used to change the speed of the induction motor.

However, it would be expensive to use this VVVF inverter for all of multiple induction motors, so it is normal to use this inverter for only one motor, as shown in Figure 1. .

FIG. 1 is a single-line circuit diagram showing a conventional example of a device for driving a plurality of pumps. In FIG. 1, a VVVF inverter 10 is connected to a commercial power source l. This VVVF inverter 10 converts AC power from a commercial power source 1 into smooth DC power using a rectifier and a smoothing capacitor. This DC power is converted into AC power with a variable voltage and variable frequency by a silice inverter and outputted.This AC power with variable voltage and variable frequency is used to drive the induction motor 15.
drive at variable speeds. Furthermore, commercial power supply 1 has switches 21 and 3.
1 are connected to induction motors 25 and 35, respectively, and a pump 16.26.36 is connected to each induction motor 15.25.35.

The fluid discharged from each pump 16, 26, 36 is collected in the collecting pipe 2 and sent towards the load, but when the flow rate required by this load changes, the fluid is collected in response to the change in flow rate. A pressure sensor 3 attached to the tube 2 detects pressure fluctuations in this fluid. The deviation between the pressure target value set by the pressure setting device 4 and the actual pressure value detected by the pressure sensor 3 is calculated at the addition point 5, and the calculation result is manually input to the pressure regulator 6, which is a proportional-integral regulator. This pressure regulator 6 outputs a control signal that makes the aforementioned deviation zero,
Based on this control signal, the inverter control circuit 7
The speed of the induction motor 15 is changed by controlling the VF inverter lO. 8 is a comparator,
When the electric motor 15 driven by the inverter 10 alone cannot reach the required flow rate, it operates in response to a signal from the pressure regulator 6 and closes the switch 21.3'l'i to increase the number of operating pumps and increase the flow rate. increase.

Reference numeral 20 denotes a drive control circuit, which includes the aforementioned pressure setting device 4, pressure regulator 6, inverter control circuit 7, and comparator 8.

FIG. 2 is an operation waveform diagram when the flow rate flowing through the collecting pipe 2 is changed from zero to the maximum and then back to zero in the conventional circuit shown in FIG. 1. This diagram shows the operation of the conventional example. explain.

FIG. 2(A) shows the change in the flow rate of the fluid sent out by the pump 16 operated at variable speed by the VVVF inverter 10.
Figure 2) and Figure 2 (C) show the flow rate changes of the pumps 26 and 36 operated at constant speed by the commercial power supply 1, respectively, and Figure 2 (B) shows the fluid pressure fluctuation in the collecting pipe 2. .

When increasing the flow rate from zero, the pumps 26 and 36 are stopped by opening the switches 21 and 31, and the speed of the pump 16 is controlled by the VVVF inverter IO to obtain the required flow rate. If the flow is insufficient even when operating at the maximum speed, the switch 21 is closed and the pump 26 is started, but since the pump 26 only operates at a constant speed, the flow rate increases rapidly. From, pump 1
If we do not reduce the flow rate by lowering the speed of 6, Figure 2 (
As shown in D), the pressure of the fluid increases rapidly. Further, when the required flow rate is insufficient, the third pump 36 is started, and at that time the pressure increases again. Conversely, when reducing the flow rate, the pumps 36 and 26, which are operating at a constant speed, are sequentially stopped, so pressure fluctuations occur at that time.

[Purpose of the invention]

An object of the present invention is to provide an inexpensive fluid machine drive control circuit that minimizes fluid pressure fluctuations even when the fluid flow rate is changed by controlling the number and speed of a plurality of fluid machines in operation. do.

[Key points of the invention]

In this invention, each electric motor that drives a plurality of fluid machines individually is provided with a switch for switching the power source, and the electric motor can be selected from either a power converter that can operate at variable speed or a commercial power source for constant speed operation. The number of fluid machines operated at a constant speed and the speed of fluid machines capable of variable speed operation are controlled in accordance with the fluid flow rate required by the load side. By configuring such a circuit, it is intended to minimize fluctuations in fluid pressure when increasing or decreasing the number of fluid machines in operation.

[Embodiments of the invention]

FIG. 3 is a single-line circuit diagram showing an embodiment of the present invention, and shows a case where three pumps are used as the fluid machine. In order to simplify the explanation, it is assumed that the three pumps and the electric motors that drive the pumps have the same capacity, but they do not need to have the same capacity.

In Figure 3, commercial power supply 1 has three sets of switching switches '12.
．． Three induction motors 15 and 25° are connected through 22.32, and these motors '15.25.35
drive pumps 16, 26, and 36, respectively. The fluids pumped by these pumps 16, 26, 36 are collected in the collecting pipe 2 and sent to the load side.

Note that since the VVVF inverter 10 that outputs variable voltage/variable frequency AC power is connected to one of the switching switches 12, 22, and 32 mentioned above, each induction motor 15, 2
5.35, by switching this switching switch 12.22.32, it is possible to select either constant speed operation using the power from the commercial power supply 1 or variable speed operation using the power from the VVVF inverter 10. can. - However, in order to reduce the cost, the capacity of the above-mentioned VVVF inverter 10 is the capacity for one induction motor that can be connected to this inverter 10 (if the capacities of the motors are different, the capacity for one motor of the maximum capacity). ).

A pressure sensor 3 for detecting fluid pressure is attached to the collecting pipe 2, and a drive control circuit 20 operates so that this fluid pressure always maintains the pressure target value set by the pressure setting device 4. There is. That is, when the pressure sensor 3 detects a change in the flow rate of the fluid required on the load side as a pressure fluctuation, the deviation between the actual pressure value from the pressure sensor 3 and the above-mentioned pressure target value is calculated at the addition point 5, The calculation result is input to the pressure regulator 6, and this pressure regulator 6
A control signal that makes the above-mentioned deviation zero is outputted from. This control signal is given to the inverter control circuit 7 and the comparator 8, and the comparator 8 controls the number of pumps operated by the commercial power supply 1 and the speed of the pumps connected to the VVVF inverter 10. This is intended to cover the required flow rate. 20 is a drive control circuit, which includes the above-mentioned pressure setting device 4, pressure regulator 6, inverter control circuit, and comparator 8.

The above operation will be explained in detail below using specific numbers. Assuming that the flow rate of fluid sent out by one pump is 100%,
The discharge amount of one 7° bong connected to commercial power supply 1 is 0% (
J at either 100% (when stopped) or 100% (when running),
The discharge volume of the pump driven by the VVVF inverter IO can be adjusted between 0% and 100% by changing its speed, so the total discharge volume of three pumps can be freely adjusted between 0% and 300%. You can choose to.

Assuming that the required flow rate on the load side is now 60%, operate the switching switch 12 to connect the motor 16 to the VVVF-inverter lO, control the output frequency of the inverter 10, and adjust the flow rate delivered by the pump 16. Make it 60%. At this time, the electric motors 25 and 35 are disconnected from the commercial power source 1 and the inverter 10 and are stopped.

If the flow rate required by the load side increases to 110% in this state, the flow rate flowing through the collecting pipe 2 is 60%, so
The pressure of this fluid fluctuates, and the deviation between the pressure target value and the actual pressure value is input to the pressure regulator 6, and a control signal for reducing this deviation to zero is output from the pressure regulator 6. With this control signal, first, the speed increase command is issued from the inverter control circuit 7 to VV.
The power is applied to the VF inverter 10, so that the electric motor 15 operates at maximum speed and the pump 16 delivers 100% of the flow rate. However, since the load side requires 110% flow rate,
The deviation between the pressure target value and the actual pressure value described above does not become zero.

Therefore, the switching switch 12 is activated by the control signal output from the pressure regulator 6 and the signal from the comparator 8, first cutting off the connection between the inverter 10 and the electric motor 16, and then immediately connecting the commercial power source 1 to the electric motor 15. do. That is, the power source of the electric motor 15 is switched from the inverter 10 to the commercial power source 1, but since the power capacity of the commercial power source 1 is 100%,
Even if the speed of the electric motor 15 is slightly reduced at the time of switching, switching to the commercial power source side can be performed without any problem. Next, after lowering the output frequency of the no-load VVVF inverter 1o to the minimum, connect either the motor 25 or 35 to this inverter 10, and then increase the motor speed until the pump discharge flow rate reaches 10%. For example, the flow rate of the fluid flowing through the collecting pipe 2 is 110%, which is the same as the flow rate required by the load side. Therefore, the deviation input to the pressure regulator 6 becomes zero, and the control signal output from the pressure regulator 6 maintains the value at that time.

As mentioned above, when the flow rate increases from 60% to 110%, according to the present invention, the flow rate increases in the order of 60% → 100% → 110%, so the process of increasing the flow rate proceeds smoothly and the pressure fluctuation However, in the case of the conventional example shown in Figure 1, the force that causes the flow rate to change in the order of 60% → 100% → 200'% → 110% causes abnormal pressure fluctuations in the process, which is inconvenient. . When reducing the flow rate, for example, when reducing the flow rate from 110% to 60%, the pump connected to the inverter 10 and operating at 10% discharge rate continues to operate and is connected to the commercial power supply 1. After the electric motor 15 is disconnected from the power source and stopped, the output frequency of the inverter 10 may be increased to make the discharge flow rate 60%. That is, at this time, the flow rate changes in the order of 110%→10%→60%, which is the same as in the conventional example. In addition, when reducing the flow rate from 110% to 60%, the speed of the pump connected to the inverter 10 and operating at 10% discharge rate is reduced to zero, and then the pump operating on the commercial power supply 1 is There is also a method of stopping the electric motor 15 and then increasing the output frequency of the inverter 10 again to make the discharge amount i60%. At this time, the discharge amount changes in the order of 110% → 100% → 0% → 60%.

FIG. 4 is an operating waveform diagram when the flow rate of fluid flowing through the collecting pipe 2 is changed from 0% → 300% → 0% in the circuit shown in FIG. 3, and FIG. The discharge flow rate of the pump 16, FIG. 4(B) is the discharge flow rate of the pump 26, FIG.
Figure (C) shows the discharge flow rate of the pump 36, and Figure 4 (CD) shows the pressure fluctuation of the fluid in the collecting pipe 2 at that time. When increasing the flow rate, the pump is switched to operate at a constant speed, and the inverter 10 controls the speed of the other pumps to increase the flow rate. Conversely, when reducing the flow rate, reduce the number of pumps operating at a constant speed using the commercial power source 1, and increase or decrease the speed of the pumps operating using the inverter 10 so that the total flow rate reaches the required value. There is.

FIG. 5 is a circuit diagram showing a second embodiment of the present invention,
A commercial power source 1, a collecting pipe 2, and a pressure sensor 3 shown in FIG.
, pressure setting device 4, addition point 5, pressure regulator 6, inverter control circuit, comparator 8, VVVF ear bar p
10, induction motor 15.25.35, pump 16.26
．． Since the reference numerals 36 and their names, uses, and functions are the same as those shown in FIG. 3, their explanations will be omitted.

In the second embodiment shown in FIG.
0 is provided with a synchronization detection circuit 9 for detecting the synchronization state between the commercial power supply l and the output of the VVVF inverter 1o.
This synchronization detection circuit 9 receives the signal from the comparator 8.
The switching switches 13, 23 and 33 are operated only when it is detected that both power supplies are in a synchronous state.

As in the first embodiment described above, the flow rate was changed from 60% to 110%.
The operation of FIG. 5, which is the second embodiment, will be described in the case of increasing the value to %. First, VVVF is set by the switching switch 13.
As in the case described above, the inverter 10 and electric motor 15 are fully connected, the pump 16 is delivering 60% flow, and the pump 26 and winnow are stopped.

If the output voltage and output frequency of this inverter 10 are increased to the same values as those of the commercial power supply 1, the pump 16 will operate at the maximum speed, and its discharge amount will be 100%.
It is. Therefore, the synchronization state of the commercial power supply 1 and the inverter 10 is detected by the synchronization detection circuit 9, and then the inverter 10
If the switching switch 13 is operated so that the inverter 1o and the electric motor 15 are connected in parallel, and the connection between the inverter 1o and the electric motor 15 is immediately disconnected, the electric motor 15 is uninterrupted and its power source is connected to the electric power source 1. Can be switched. Therefore, if the output frequency of the inverter 10 is set to the lowest, then the inverter 10 and the electric motor 25 are connected, and the speed of the pump 26 is then adjusted so that the discharge amount becomes 10%, a flow rate of 110% can be obtained. The flow rate change at that time is 60% → 100X → 11
Since the pressure increases smoothly to 0% and the power source of the motor 15 is switched without interruption, there is no pressure fluctuation at that time.

Next, when reducing the flow rate from 110% to 60%, gradually reduce the speed of the pump 26 connected to the inverter 10 and operating at a discharge rate of 10%, and when the flow rate reaches zero, the inverter 10 +qtt from the electric motor 25. Next, the output voltage and frequency □ of the inverter 10 are set to the same values as those of the commercial power supply 1, and when the synchronization detection circuit 9 detects that the two are in a synchronous state, the switching switch 13 connects the two in parallel. If the commercial power supply side is immediately turned off, the power supply of the motor 15 can be switched from the commercial power supply 1 to the inverter 10 without interruption, so after that, the output frequency of the inverter 10 is adjusted to make the discharge amount of the pump 16 60X. Bye. In other words, the decrease in flow rate is 110%→100%→
Since it is performed smoothly in the order of 60%, no abnormal pressure fluctuation occurs.

FIG. 6 is an operation waveform diagram when the flow rate of the fluid flowing through the collection pipe 2 is changed from 0% → 300% → O% according to the circuit shown in FIG. 5, and FIG. 6 (A) IB).

(C) shows the discharge flow rate of pumps 16, 26, and 36, but the discharge flow rate of each pump is increased or decreased when it is connected to the inverter 10, and the number of pumps in operation cannot be changed. Since the power supply 1 and the inverter 10 are connected in parallel and then switched without interruption, there is almost no pressure fluctuation due to increase or decrease in the discharge flow rate. FIG. 6(D) shows the pressure in the collecting pipe 2, and it is noted that there is no fluctuation in the pressure.

〔Effect of the invention〕

According to this invention, by switching the power source of the electric motor that separately drives a plurality of fluid machines between a power conversion device such as a VVVF inverter that can operate the electric motors at variable speeds and a commercial power source, the total amount discharged by the fluid machines can be changed. Fluid pressure fluctuations when increasing or decreasing the number of operating fluid machines to change the flow rate can be minimized. The power converter required at this time only needs to have the capacity to drive one electric motor with the maximum capacity, so there is no difference from the conventional method, and only a few additional devices such as a switching switch are required, so it is low cost. It has the advantage of minimizing pressure fluctuations at a low cost.

[Brief explanation of drawings]

FIG. 1 is a single-line circuit diagram showing a conventional example of a plurality of pump drive devices, and FIG. 2 is an operating waveform diagram in the circuit shown in FIG. 1. FIG. 3 is a single-line circuit diagram showing an embodiment of the present invention, FIG. 4 is an operating waveform diagram in the circuit shown in FIG. 3, and FIG. 5 is a single-line circuit diagram of the second embodiment of the present invention. FIG. 6 is an operating waveform diagram in the circuit shown in FIG. 5.

Claims (1)

[Claims] In a device that controls the fluid to be delivered by changing the number and speed of a plurality of fluid machines that are individually driven by electric motors, the device has a capacity that can drive the maximum capacity of the electric motors, and is connected. a power conversion device that controls the speed of the motor, a switching switch provided in each motor that can switch the motor drive power to either the power conversion device or the commercial power source, and the number of motors driven by the commercial power source. and a drive control circuit that controls the speed of the electric motor driven by the power conversion device in accordance with the state of the fluid.