JPS6299700A - Fluid delivery control method - Google Patents

Abstract

PURPOSE:To make it possible to operate a fan motor safely, by controlling the rotating speed of the fan motor, stepwise according to the flow, and controlling the minute variation of flow in each step, by a flow control means, so as to avoid resonance point of a rotor such as a fan. CONSTITUTION:Continuous control signal Y of a control device 11 is fed to VVVF 3, after being converted into stepwise signals Y0, Y1, Y2...Yk by an input converter 16. Here, assuming that frequency control input toward VVVF 3 is Yi (Yi-1<Y<Yi), output frequency of VVVF 3 is varied stepwise by this Yi, and the rotating speed of a fan motor 4 is varied stepwise, as a result. On the other hand, output of the control device 11 and output of the input converter 16, that is, deviation of stepwise control input Y0, Y1...Yk from demand command of the load of the control input device 11, is given by a deviation signal unit 17, the opening of a damper 8 is controlled by said deviation, and the flow is controlled finely to the desired value which corresponds to the demand gas quantity. Accordingly, resonance point of a rotor is avoided, and the fan motor 4 can be operated safely.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a fluid delivery control system for controlling stepwise f of fluid delivered to a fan motor.

[Previous i-jutsu]

FIG. 4 is a block connection diagram of a conventional fluid delivery control device. In the figure, 1 is a commercial power supply, 2 is a switch, 3 is a variable frequency power supply (hereinafter referred to as VVVF'), 4 is a fan motor, and 5 is a fan. (tF including vane), 6' is the connecting shaft, 7
7a and 7b are air input and output channels for the air sent out by the fan 5; 0.8 are dampers housed in the air channel 7 as flow control means; 9 is a drive for the damper 8; 1) is a control device that generates a control input to the VVVF 3 and the damper drive device [10;
is a transformer, 13 is a rotation speed detector, 14 is a load detector, 1
3a and t3b are contacts that close and open, respectively, when the rotation speed detector 13 is activated, and 14a and 14b are load detectors 14.
Contacts that close and open respectively when activated, 15 is VV
Fixed control input terminal 18 is a control input terminal to drive device 10 which provides a signal for which the output of VF 3 is constant.

Next, the operation will be explained.

This fluid delivery control device prevents the rotational speed of the fan motor 40 from falling below a certain rotational speed NL with respect to the setting scenery (flow rate) QL, and when the wind is below this wind tQL, the damper 8 is turned off as shown in FIG. The opening degree is made smaller, and specifically, the following control is performed. That is, the output frequency f and the output voltage V of the variable same-wavenumber power supply 3 have a functional relationship, and once the frequency f is determined, the output voltage V is uniquely determined. That is, equation (1) holds true.

V=g(f) ・・・・・・・・・・・・・・・
(1) However, 1g: Function In order to avoid saturation of the motor windings, it is common to use the relationship shown in equation (2).

g(f),,-,f ・・・・・・・・・・・・
(2) However, K: Constant From the above explanation, it is understood that the output frequency f can be detected from the output voltage V of the variable frequency power supply 3. Therefore, the town! If the output voltage V of the same wave number power supply 3 is changed to a value suitable for measurement via the transformer 12 and a value below a certain value is detected, the frequency f, and therefore the rotation speed N from equation (1), is detected to be below the certain value NL. A rotation speed detector 13 is obtained.

If the rotational speed N is greater than the fixed value NL, the rotational speed detection 513 is inactive, and therefore the load detector 14 is also inactive, so the contacts 13a and 14aid are open and the contacts 13b and 14b are closed. Therefore, at this time, the variable frequency power supply 3 has the control device 1.
), control inputs are applied to the damper drive device 10, and in FIG.
Within this range, the damper opening degree θC is close to fully open.

When the rotational speed N is about to fall below a certain value NL, the rotational speed detector 13 is activated and the contact 13. is closed, and contact 13b is opened. Contact point 13. When the contact 14a is closed, the load detector 14 is activated, but if the airflow Q is smaller than the airflow QL corresponding to the rotational speed NL, the load detector 14 is set to be inactive.
, 14b are open and closed, respectively. Therefore, at this time, a fixed control input is given to the variable frequency power supply 3, and the rotation speed is fixed at NL, and a control input of the control device [1] is given to the damper drive device [10], so that the wind speed is less than or equal to tQL. In the range of , the output frequency fL of the variable frequency power supply 3 is r L : NL
... It is fixed at the value of (3), and this situation is shown in Figure 5 (A).

When the control signal from the control device 1) is given to the damper drive device 10, the damper 8 is operated so that the required air volume is achieved, and the sedan bar 8t is shrunk to the air volume Qt as shown in FIG. 5(a). Become. Next, a method of returning to the original damper opening degree θC when the wind tQ becomes equal to or higher than Qt from the above state will be explained.

When the rotation speed detector 13 is operating, the contact 18.
is closed and the load detector 14 is activated.

When the required air volume increases and the control signal of the control device full increases, and the damper opening degree θ reaches θC, the load detector 14 is activated and its contacts 14a and 14b't are closed and opened, respectively. Therefore, a control input 10+ is given to the damper drive device 10 so that the damper opening degree θ0 is fixed, and a signal from the control device t1) is given to the variable frequency power supply 3, and if the output frequency f is further increased, , the rotation speed detector 13 returns to its original state of wind 1iQL-100%.

[Problems that the invention attempts to solve]

Since the conventional fluid delivery control system is as described above, it is possible to control the fan motor 4 so that it changes continuously in the rotation speed range from NL to 100%. If there is a resonance point with the mechanical vibration frequency, the mechanical vibration is amplified, causing problems such as damage to the fan 5.

This invention has been made to solve all of the above-mentioned problems, and even if the mechanical resonance point as mentioned above is in the operating power supply frequency range while the fan motor 4 is rotating, the fan motor 4 can be safely operated. and a fluid delivery control device that can rotate the fan.

[Means for solving problems]

The fluid delivery control method according to the present invention controls the rotation speed of a fan motor that delivers all of the fluid in a plurality of stages, and also controls minute changes in the flow rate at each stage by a flow rate control means.

[For production]

The variable frequency power supply in the present invention supplies the fan motor with a variable frequency output that changes stepwise, and acts to prevent all rotational speed modes in the rotational range of the fan motor in which mechanical resonance occurs. Further, the flow rate control means such as a damper acts to control the change in the flow rate between each rotational speed range, which changes stepwise. Therefore, as a result, flow rate control that changes randomly becomes possible.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

In FIG. 1, 16 is an input converter that converts the continuous control signal output by the control device 1) into a stepwise signal, and 17 is a deviation signal device that generates a signal corresponding to the deviation between the continuous control signal and the stepwise signal. It is. Note that other components that are the same as those shown in FIG. 4 are designated by the same reference numerals, and redundant explanation thereof will be omitted.

Next, the operation will be explained.

Now, when the fan motor 4 is driven σ, the fan 5 receives a mechanical shock due to a change in air pressure every time each blade of the fan 5 passes through the lower exit part b of the air passage 7, as shown in FIG. It turns out.

Here, the number of blades is 21 fan 5 rotating deposit X (
RPM), the frequency R of the above mechanical shock is 2φX(RPM), and the fan 5. In particular, it is highly likely that the natural frequency matches the natural frequency of the fan 5, which has a complex structure and a large number of blades. Note that resonance occurring in the mechanical system includes resonance caused by mutual vibrations among the fan motor 4, fan 5, and connecting shaft 6. In this invention, the continuous control signal Y of the control device 1)
i, stepwise signals Yo, Y+, Y by the input converter 16
2. ...converted to YK and supplied to VVVF'3.

Here, V V V F 3 (D Frequency m Controller 7
1 k Yi (Yi-+ < Y < Y i ), the output frequency of the VVVF3 changes stepwise due to this Yi, and as a result, the fan motor is changed to nl, n2 . ....

Change it like nK.

On the other hand, each output of the control device [1) and the input converter 16, ie, the stepwise control human power Yo, Y+, . . .

The deviation between the YK and the load request command of the control input device 1) is determined by the deviation signal device 17, and the drive device is actuated by a signal corresponding to the deviation, thereby controlling the opening degree of the redamper 8. Fine adjustment is made to the target value corresponding to the required air volume based on the signal. Therefore, the quantity Q in the request is Ql-1≦Q≦Q1 ・・・・・・・・・・・・
In the case of (4), the rotation speed N of the fan motor 4 is n, and the damper 8 changes between the opening degrees θC and θd. In this way, the number of revolutions N (i- is selected in stages,
The frequency (number of rotations) at which the fan 5 and the like resonate can be made not to overlap the number of rotations of a normal fan motor.

In the above embodiment, the fan 5 is connected as the load of the fan motor 4, but the load is not limited to the fan, but may be another rotating body such as a pump.

Further, although the case where the air volume is controlled by the air flow rate plate 8 has been described, any other mechanical control mechanism such as a vane or a valve can produce the same effect.

Furthermore, in order to simplify the explanation, in Fig. 3, we have explained the case where the damper opening degree changes between θC and θd, but θC and θd are different values between each air volume Q1-1 to Q1. It's okay to have one.

In addition, in the above explanation, the resonance point was explained as being avoided, but in the fan 5, etc., there are areas where operation is prohibited, such as a surging area where operation is unstable, and the present invention can also be used to avoid these areas. is effective and can be widely used to avoid operating prohibited areas for rotating bodies such as general fans.

Furthermore, as a secondary effect, since the damper 8 performs minute adjustment of the load, in order to increase the speed in the direction of decreasing rotation speed,
Conventionally, the VVVF 3 required a regenerative device, but this method eliminates the need for a regenerative device.

〔Effect of the invention〕

As described above, according to the present invention, the fan motor driven by the variable frequency power supply is operated so that the rotation speed of the rotating body such as the fan changes in stages, so that the resonance point of the rotating body such as the fan is The fan motor can be operated safely by avoiding this. In this way, it is possible to completely prevent accidents such as damage to the fan as in the prior art.

[Brief explanation of drawings]

Fig. 1 is a block connection diagram for explaining the entire fluid delivery control system according to an embodiment of the present invention, Fig. 2 is a schematic configuration diagram of a mechanical resonance point generation site, and Fig. 3 shows the rotation speed and damper opening with respect to air volume. FIG. 4 is a block connection diagram of a conventional fluid delivery control device, and FIG. 5 is a conventional characteristic diagram of rotation speed and damper opening with respect to air volume. :H- is a variable frequency power supply, 4 is a fan motor, 5 is a fan, 8 is a flow rate control means, 1) is a control device, 16 is an input converter, and 17 is a deviation signal device. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. Figure 4 Figure 5

Claims (2)

[Claims] (1) In the fluid supply control method described above, a fan motor is operated by a variable frequency power supply whose output frequency changes according to a load request command, and the amount of fluid sent out by this fan motor is controlled by a flow rate control means. A fluid delivery control system characterized in that the rotational speed of a fan motor is controlled in stages according to the flow rate, and minute changes in the flow rate at each stage are controlled by the flow rate control means. (2) Fluid delivery control according to claim 1, characterized in that the flow rate control means is controlled based on the deviation between the load request command and the stepwise control input to the variable frequency power source. method.