JP2005045922A - Pump control method and pump controller - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To offer a pump control method and a pump controller which does not affect a motor by the temperature rise of a pump drive motor even if the user varies the frequency to the second frequency (for example, 60Hz) being the maximum frequency the specified frequency higher than the first frequency, using a pump of the specified first frequency (for example, 50Hz). <P>SOLUTION: This pump controller possesses a control means which controls the rotational speed so that the current value of the pump drive motor may come to a preset current value or its vicinity. The control means possesses a function of speed-variably operating the pump for the specified first frequency (50Hz) until the second frequency (60Hz) the specified frequency higher than the first frequency, operating it at a certain voltage/frequency ratio α1 between 0Hz and the first frequency (50Hz), operating it at a voltage/frequency ratio (Vc/50), where the temperature rise of the pump drive motor becomes minimum, with the first frequency (50Hz), and operating it at a certain voltage/frequency ratio α2 between the first frequency (50Hz) and the second frequency (60Hz). <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to pump control devices such as sewage, filth, and submersible submersible water pumps, and more particularly to a pump control method and pump control device that take into account the temperature rise of a pump drive motor and the mechanical life of the pump.

  Normally, the current characteristics of the centrifugal pump have a characteristic that the current value I increases as the flow rate Q increases, as shown in FIG. Therefore, it is possible to improve the pump performance by increasing the rotation speed on the small flow rate side to the rated current value Is. As shown in FIG. 3, the conventional method for controlling the rotational speed of a driving motor is to control the voltage / frequency ratio (V / F) to a constant value β up to a set maximum frequency (maximum allowable frequency) (60 Hz). Alternatively, the voltage / frequency ratio (V / F) is set to a constant value α up to a certain frequency (here, 50 Hz), and control is performed at a constant voltage (here, 200 V) from point a on the way.

  In these control methods, when the pump driving motor for 50 Hz is operated at a variable speed up to its maximum frequency of 60 Hz, the temperature rise of the pump driving motor during 50 Hz operation is not operated at the optimum point. This is a distribution as shown in FIG. 5, where the temperature rise distribution of the pump drive motor takes the voltage / frequency ratio (V / F) on the horizontal axis and the motor temperature rise (T) on the vertical axis. This is because the driving electric motor is not operated at the voltage / frequency point (point c in FIG. 5) at which the temperature rise is minimum.

  In particular, when the voltage / frequency ratio (V / F) is controlled to be constant, the voltage during 50 Hz operation is lowered (see point b in FIG. 3), so the voltage / frequency ratio (V / F) is It becomes very small and the temperature rise of the pump drive motor becomes high (see point d in FIG. 5). In some cases, it may be higher than the heat resistance class of the pump drive motor. Therefore, using the 50 Hz pump drive motor with the conventional control method to perform variable speed operation has the drawback of shortening the life of the pump drive motor. In order to prevent this, a pump that performs variable speed operation has to select and cope with an impeller so that the temperature rise of the motor for driving the pump is within an allowable value at the maximum frequency.

  For this reason, when the maximum frequency is set to 60 Hz, an impeller for 60 Hz is selected, and the pump performance is improved by the rotational speed control as shown in FIG. 2, that is, the pump performance by the rotational speed control from the normal pump performance curve e. The improvement to the curve f cannot be obtained. In order to improve pump performance, it is necessary to set the maximum frequency to 60 Hz or more.

  In order to improve the pump performance as described above, it is necessary to set the maximum frequency to 60 Hz or more. However, since the pump drive motor is usually designed at 50 Hz or 60 Hz, the pump drive is performed at 60 Hz or more. When the electric motor is operated, the rotational speed of the pump becomes higher than the design point, so that there is a drawback that the life of the bearing, the mechanical seal, etc. is shortened. The present invention has been made to solve this problem. A pump for a predetermined first frequency (for example, 50 Hz) is used, and a second frequency (for example, a maximum frequency higher than the first frequency by a predetermined frequency) An object of the present invention is to provide a pump control method and a pump control device that do not affect the electric motor due to a temperature rise of the electric motor for driving the pump even if it is variable up to 60 Hz).

  In order to solve the above-mentioned problem, the invention according to claim 1 is a pump control method for controlling the rotational speed so that the current value of the pump driving motor is in the vicinity of a preset current value, and has a predetermined first frequency. The pump driving motor is operated at a variable speed to a second frequency that is higher than the first frequency by a predetermined frequency, and the voltage / frequency ratio at the first frequency is set to a value that minimizes the temperature rise of the pump driving motor, Between the first frequency and the second frequency, the ratio of voltage increase / frequency increase is controlled as a constant value.

  According to a second aspect of the present invention, in the pump control method of the first aspect, the first frequency is 50 Hz and the second frequency is 60 Hz.

  The invention according to claim 3 is a pump control device comprising a control means for controlling the rotational speed so that the current value of the electric motor for driving the pump is in the vicinity of a preset current value, wherein the control means is a predetermined value. The pump for the first frequency is operated at a variable speed up to a second frequency that is a predetermined frequency higher than the first frequency, and the voltage / frequency ratio at the first frequency is set to a value that minimizes the temperature rise of the pump driving motor. The first frequency to the second frequency have a function of controlling the ratio of voltage increase / frequency increase as a constant value.

  According to a fourth aspect of the present invention, in the pump control device according to the third aspect, the first frequency is 50 Hz and the second frequency is 60 Hz.

  According to the invention described in each claim, the following excellent effects can be obtained.

  According to the first and second aspects of the present invention, variable speed operation is performed from the first frequency to the second frequency (maximum allowable frequency) (for example, 60 Hz) using a pump for a predetermined first frequency (for example, 50 Hz). In this case, by setting the operating point at the first frequency to a voltage / frequency ratio that minimizes the temperature rise of the pump drive motor, a pump control method that enables operation while suppressing the temperature rise of the motor is provided. Can be provided. Also, the pump can be used at the same level as a pump that does not perform variable speed operation.

  According to the third and fourth aspects of the present invention, the control means operates the pump for a predetermined first frequency at a variable speed up to the second frequency, and sets the voltage / frequency ratio at the first frequency to the pump drive. The temperature rise of the pump motor is increased because the temperature rise of the motor is minimized, and the ratio between the voltage increase / frequency increase is constant between the first and second frequencies. It is possible to provide a pump control device that can be operated while suppressing the above. Further, it can be used at the same level as a pump that does not perform variable speed operation.

  Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a diagram showing a configuration example of a pump control apparatus according to the present invention. Reference numeral 1 denotes a centrifugal submersible pump for sewage, filth, and miscellaneous drainage, and reference numeral 2 denotes a pump driving motor that drives the submersible pump 1. Reference numeral 3 denotes an inverter that supplies driving electric power to the pump driving electric motor 2, and reference numeral 4 denotes a control unit that controls the inverter. Reference numeral 5 denotes a current sensor that detects the current value of the driving power supplied to the pump driving motor 2, and reference numeral 6 denotes a voltage sensor that detects the voltage value of the driving power supplied to the pump driving motor 2. And the voltage value V detected by the voltage sensor 6 are input to the control unit 4. The control unit 4 is connected to a current setting unit 7 for setting a rated current value Is, a voltage / frequency ratio setting unit 8 for setting a voltage / frequency ratio (V / F), and a maximum frequency setting unit 9. .

  AC power is supplied to the inverter 3 from the AC power source 10, and the control unit 4 rotates the submersible pump 1 so that the current value I of the pump driving motor 2 is close to the rated current value Is preset by the current setting unit 7. Control the number.

  In Japan, pump drive motors that drive this type of submersible pump are normally resistant to temperature rises of the pump drive motor 2 regardless of the three ratings (50 Hz / 200 V, 60 Hz / 200 V, 60 Hz / 220 V). Since it is designed not to exceed the class, the design point of the motor 2 for driving the pump is not necessarily one of the three ratings. The temperature distribution of the pump drive motor 2 at each operating point is as follows: the horizontal axis represents the voltage / frequency ratio (V / F) at 3 ratings, and the vertical axis represents the corresponding temperature rise value (T). As described above, the distribution is as shown in FIG. In FIG. 5, the point c at which the temperature rise value of the pump driving motor 2 is the lowest is usually a design point of the pump driving motor 2.

  Here, the control when the impeller of the pump uses 50 Hz will be described. In the variable speed control of the submersible pump 1, the maximum frequency (maximum allowable frequency) is set in the maximum frequency setting unit 9 as Fs = 60 Hz. The control unit 4 controls the pump 1 by controlling the pump driving motor 2 as described below.

  When the flow rate (Q) of the submersible pump 1 is small, the maximum frequency Fs set by the maximum frequency setting unit 9 because the current value I of the pump drive motor 2 is lower than the rated current value Is as shown in FIG. By increasing the rotational speed to 60 Hz, the performance is improved from the normal pump performance curve e in FIG. 2 to the pump performance curve f by rotational speed control. On the other hand, when the flow rate of the submersible pump 1 is large, the current value I of the pump driving motor 2 approaches the rated current value Is, and therefore the frequency approaches 50 Hz. When operating at 50 Hz, the horizontal / axis takes the voltage / frequency ratio (V / F = 200/50, 200/60, 220/60) at 3 ratings (50 Hz / 200 V, 60 Hz / 200 V, 60 Hz / 220 V), The operation is performed at a voltage / frequency ratio (V / F) (point c in FIG. 5) at which the temperature rise is lowest when the vertical axis represents each motor temperature rise (T). That is, as shown in FIG. 4, operation is performed with a voltage / frequency ratio α1 having a constant value set by the voltage / frequency ratio setting unit 8 between frequencies 0 to 50 Hz, and at a voltage value Vc at point c in FIG. 5 at 50 Hz. The operation is performed at a constant voltage / frequency ratio α2 set by the voltage / frequency ratio setting unit 8 between 50 Hz and 60 Hz.

  By controlling the pump driving motor 2 that drives the submersible pump 1 as described above, even a 50 Hz pump can be operated at a variable speed. Since the maximum frequency is 60 Hz, that is, the highest frequency of the above three ratings (50 Hz / 200 V, 60 Hz / 200 V, 60 Hz / 220 V), mechanical parts such as bearings and mechanical seals can withstand this rotational speed. Because of the design, the service life is equivalent to a pump that does not perform variable speed operation.

  In addition, mechanical parts such as pumps and pump drive motor bearings and mechanical seals are usually designed to withstand the maximum allowable frequency (second frequency) of the pump drive motor, so variable speed operation is performed. It can be used at the same level as no pump.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the technical idea described in the claims and the specification and drawings. Is possible.

It is a figure which shows the structural example of the pump control apparatus which concerns on this invention. It is a figure which shows the relationship between the flow volume of a pump, an electric current value, and a head. It is a figure which shows the relationship between the frequency and voltage in the conventional pump control driving | operation. It is a figure which shows the relationship between the frequency and voltage in this invention and the conventional pump control driving | operation. It is a figure which shows the relationship (temperature distribution) of the motor temperature rise with respect to voltage / frequency ratio.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Submersible pump 2 Pump drive motor 3 Inverter 4 Control part 5 Current sensor 6 Voltage sensor 7 Current setting part 8 Voltage / frequency ratio setting part 9 Maximum frequency setting part 10 AC power supply

Claims (4)

A pump control method for controlling the rotational speed so that a current value of a pump driving motor is close to a preset current value,
The pump driving motor for a predetermined first frequency is operated at a variable speed up to a second frequency that is a predetermined frequency higher than the first frequency, and the voltage / frequency ratio at the first frequency is minimized so that the temperature rise of the pump driving motor is minimized. A pump control method characterized in that the ratio between the increase in voltage / the increase in frequency is controlled as a constant value between the first frequency and the second frequency. The pump control method according to claim 1,
The pump control method according to claim 1, wherein the first frequency is 50 Hz and the second frequency is 60 Hz. A pump control device comprising a control means for controlling the rotational speed so that the current value of the pump drive motor is close to a preset current value,
The control means operates the pump for a predetermined first frequency at a variable speed to a second frequency that is higher than the first frequency by a predetermined speed, and increases the voltage / frequency ratio at the first frequency to increase the temperature of the pump driving motor. Has a function of controlling the ratio of the increase in voltage / the increase in frequency as a constant value between the first frequency and the second frequency. The pump control device according to claim 3,
The pump control device according to claim 1, wherein the first frequency is 50 Hz, and the second frequency is 60 Hz.

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