JP2010276006A - Pump number control by pump shaft power - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems of conventional water supply secondary pump number control in which since the number control is performed by a system using a two-position regulator by load flow measurement or by use of a number control controller, attachment of a flowmeter to a pipe is needed, the cost is increased due to the necessity of the flowmeter body and incidental piping work and wiring work and, further, although appropriate flow control is performed by pump rotating speed according to the number control by adopting an inverter for water supply pressure control, pump shaft power is not taken into consideration since the increase/decrease number of pumps is determined based on a pump rated flow rate. <P>SOLUTION: In the pump number control, setting of a flowmeter is dispensed with, and pressure control that is indispensable for variable flow water supply control is used. In response to a pressure signal from a terminal pressure transmitter or terminal differential pressure transmitter, a number control controller calculates the pump shaft power from a control output of a pressure regulator according to the frequency state of an inverter pump under operation, the number of operating pumps and the state of a control bypass valve, and increase/decrease stage determination is executed based on the calculation result to perform the pump number control with an appropriate pump shaft power. This number control includes a high energy saving effect. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to control of the number of heat source water supply secondary pumps for heat exchangers.

  Conventional control of the number of secondary water pumps uses a flow meter to measure the load flow of cold water or hot water by load flow measurement, and controls the number of units by turning on and off the two-position controller. A method of supplying water to the load by increasing / decreasing the number of pumps suitable for the load based on the result of calculating the average value for a certain period of time is widely known.

JP 2000-265967 A JP-A-8-261190

  The conventional control of the number of secondary water pumps controls the number of units by turning on and off the two-position controller based on load flow measurement, or the number control controller controls the number of units, so it is necessary to attach a flow meter to the water supply pipe. Piping work and wiring work are necessary, and the cost is high.

  In recent years, an inverter has been adopted to control the number of pumps to control the pump rotation speed by controlling the pump rotation speed. Is not taken into account.

  Also, the water pressure control is a terminal pressure control or terminal differential pressure control system that controls the pressure at the terminal on the water supply load side than the water source pressure control, and energy saving effect is obtained by water supply that matches the flow rate of the heat exchanger on the load side. In recent years, it has been adopted in many water secondary pumps, but the pressure transmitter or differential pressure transmitter attached to this end is not used effectively.

  In the present invention, the pressure control from the terminal pressure transmitter or the terminal differential pressure transmitter is used to calculate the shaft power of the pump based on the pump inverter frequency state and the pressure bypass valve opening state during operation from the control output signal of the pressure regulator. The bypass flow rate is judged and the number of pumps is controlled.

  The present invention has the following effects.

  The flow meter body, piping work and wiring work are unnecessary and the cost can be reduced.

  Although an inverter is required for the pump, the unit controller can properly determine the number control of the pump in consideration of the shaft power of the pump and respond to the heat exchanger load, thus reducing the running cost without using wasted energy and saving energy Can contribute to the reduction of global warming gas O2 emissions.

It is an Example of the unit control controller control block diagram of this invention. It is a block diagram of a number control controller. It is a heat source instrumentation figure for heat exchangers. (A) is a pressure regulator control output graph. (B) is an inverter operation | movement and a bypass valve opening degree operation | movement graph. (C) is a pump flow rate proportional curve. (D) is a pump discharge pressure proportional curve. (E) is a pump shaft power proportional curve diagram. It is a heat source water supply piping resistance diagram for heat exchangers, and a pump operation pressure diagram. It is an increase / decision judgment figure of unit control by a water supply piping resistance diagram and a pump operation pressure diagram.

  FIG. 3 is a heat source instrumentation diagram for a heat exchanger. A pressure signal is input to a pressure regulator 2 from a terminal differential pressure transmitter 3 attached to the end of a water supply pipe, and a controlled control output signal is input to a converter 4 for output. The pump inverter 6 performs appropriate water pressure control by controlling the rotational speed of the water pump 5 and adjusting the opening of the pressure control bypass valve 7.

  The control output from the pressure controller 2 is input to the unit control controller, and the number of pumps is controlled by executing the increase / decrease stage determination based on the result of the shaft power calculation based on the control output signal and the number of operating units.

  FIGS. 4A and 4B are control signal graphs of the pressure control regulator, and the signals are input to the converter 4 as an example of the output of the converter 4B. As shown in the graph of FIG. It shows a case where the operation is performed at a frequency of 100% and the pressure control bypass valve is operated from 0% to 100%.

  FIG. 5 is a graph showing the flow rate (C), the discharge pressure (D), and the shaft power (E) of the three-phase electric motor for the pump. The flow rate is proportional and the discharge pressure is proportional to the square. The shaft power of the three-phase electric motor for pumps is proportional to the third power, so when operating at a frequency of 100%, the flow rate, discharge pressure, shaft power is 100% and the frequency is changed to 60%. The flow rate is 60%, the discharge pressure is 36%, and the shaft power of the pump three-phase electric motor is 21.6%.

  Therefore, 60% of the two pumps consume 43.2% of the shaft power of the pump three-phase electric motor and 120% of the water supply flow rate is higher than that of 100% with one pump.

  FIG. 6 is a resistance diagram of the heat source water supply piping for the heat exchanger. As the flow rate increases, the piping resistance also increases. As a water supply pressure at this time, the water pump shows a pressure 14 required as a load side water supply pressure. Become.

  FIG. 6 shows a single operation 9b, a two operation 10b as an example of the pump single operation 9a, a two operation 10a, a three operation 11a, a four operation 12a, and an inverter minimum set frequency in the rated operation when controlling the number of pumps. The pressure diagram of 3 unit operation 11b and 4 unit operation 12b is shown.

  In the conventional control of the number of pumps by the flow rate control, the step increase point 15 is set according to the rated value of the pump, and when the flow rate exceeds the step increase set flow rate for a certain time, the pump step increase is executed and when the flow rate control falls below the step decrease point 16 for a certain time. Perform step reduction.

  FIG. 7 is a graph showing the resistance diagram 13 of the embodiment of the present invention and the diagram of the pressure 14 required as the supply pressure, in addition to the rated operation of the single pump operation 9a, the dual operation 10a, and the minimum set frequency by the inverter. As an example, a pressure diagram 9c when the frequency is increased by inverter operation of one pump is shown in the pressure diagram showing single operation 9b and stand operation 10b.

  If this pressure diagram is confirmed, there will be a point where the pressure diagram 9c of the single unit operation with the frequency increased by the inverter exceeds the pressure diagram 10b when two units are operated at the lowest frequency. At this time, as a result of comparing the shaft power increased in frequency with one unit and the shaft power operated at the lowest frequency of two units, it is more appropriate to feed water to the load side with two pumps if the shaft power of two units is small In addition, energy-saving unit control is possible.

  The increase / decrease stage of the pump determines the optimum shaft power by the program calculation of the unit controller, and the pump increase stage is executed. In the decrease stage, the pressure control bypass valve 7 begins to open after the frequency of the inverter becomes the minimum by reducing the water flow rate. Pump destage is executed when the predetermined opening is exceeded.

  Although FIG. 3 shows a form in which the terminal differential pressure is measured by the terminal differential pressure transmitter 3, the effect of the present invention is the same even in the form of the pressure transmitter taken out from the heat exchanger upstream pipe at the terminal. is there.

  Figure 1 shows a comparison of the value obtained by calculating the pump shaft power by the pressure control signal and multiplying the number of operating units by the pressure control signal and the value obtained by multiplying the minimum pump frequency by the number of operating units plus one shaft power Then, the pump is cut off after the set-up timer is up.

  The pump discharge pressure correction is carried out by adding the operation number correction value to the value obtained by multiplying the minimum pump frequency by the number of operating units plus one shaft power.

  The step-down step is performed after the pressure control bypass valve is over a certain opening degree after the pressure control signal falls to the lowest frequency of the pump inverter, and the step-down timer is set up after the step-down timer is set up.

  After the increase or decrease step is executed, an effect waiting timer is set as the time to stabilize the pressure control, and the next increase / decrease determination is executed.

  FIG. 2 shows a block diagram of the unit control controller, but the effect of the present invention is the same even if the pressure control unit, the inverter output signal, and the pressure control bypass output signal are provided.

1. Unit control controller 2, differential pressure regulator 3, differential pressure transmitter 4, converter 5, water pump 6, inverter 7, bypass valve 8, heat exchanger 9, pump discharge pressure diagram when one unit is operating 10, Pump discharge pressure diagram for two-unit operation 11, pump discharge pressure diagram for three-unit operation 12, pump discharge pressure diagram for four-unit operation 13, water supply pipe pressure loss diagram 14, required water supply pressure diagram 15, pump increase Stage point 16, pump reduction stage 201, pressure control signal 401, inverter operation graph 402, pressure control bypass valve operation graph

Claims (1)

  In the pump number control method that uses multiple pressure-controllable pumps and does not use a load flow meter using terminal pressure control or terminal differential pressure control, the pump shaft power is virtually controlled by the number control controller using the pressure control output signal. A method for controlling the number of pumps to be operated, wherein the number of pumps is controlled by a pump operation step increase request and a pump operation step reduction request based on a water supply pressure control bypass valve opening.

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