JPH037040B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a variable frequency power supply system that increases or decreases the output frequency of a variable frequency power supply that controls the rotational speed of an electric motor in accordance with a load.

[Conventional technology]

Figure 1 is a diagram showing a conventional variable frequency power supply (hereinafter abbreviated as V power supply) system. In the figure, 1 is the product power supply, 2 is the V power supply, and 3 is the motor whose rotation speed is controlled by this V power supply. , 4 is a fan, 5 is a coupler connecting this fan and the electric motor 3, 6 is a vane, 7 is a drive device for the vane 6, 8 is a control input to the drive device 7, 9 is a control input to the V power supply 2, Reference numeral 11 indicates a wind channel, 11a and 11b indicate the inlet and outlet of the wind channel, respectively, and θ indicates the opening degree (angle) of the vane 6. Further, FIG. 2 is a Q-θ characteristic curve showing the relationship between the vane opening degree θ shown in FIG. 1 and the load air volume Q of the motor 3 passing through the air passage 11.

Next, the operation will be explained. The V power source 2 receives electric power from the commercial power source 1, converts it into a frequency corresponding to the desired rotation speed of the electric motor 3, and supplies the electric power to the electric motor 3.
Performs rotation speed control. Electric motor 3 drives fan 4 via coupler 5 . The fan 4 sucks air from the inlet 11a of the air passage 11 and sends out an air volume Q to the outlet 11b. A vane 6 is placed in the wind path 11,
The air volume Q can be changed depending on the opening degree θ. Also, when changing the air volume Q, in addition to the vane 6,
This can also be implemented by changing the output frequency (F) of the power source 2 and changing the rotational speed (N) of the electric motor 3, that is, the fan 4, according to equation (1). The air volume Q and the rotation speed N have a proportional relationship as shown in equation (2).

N = 120 There is a relationship like this, and when the air volume Q obtained when the vane opening degree θ is 90° (fully open) is 100%,
When θ is around 90°, the airflow rate is curvilinear with almost no change.

During operation with the normal V power source 2, the required amount of load (air volume Q) is given as the control input 9, and the output frequency F of the V power source 2 is changed to satisfy the request. At this time, the vane 6 has a vane opening angle θ from the control input 8.
receives a signal fixed at a predetermined value around 90 degrees, and is fixed at that constant opening degree. From the viewpoint of energy saving, if the vane opening angle θ is made smaller, the energy saving effect will be reduced, so θ is set around 90°.

Since the conventional variable frequency power supply system is configured as described above, when the load (air volume Q) reduction request control input 9 is received, the inertia of the shaft system (GD ² ) of the system such as a fan is large. So Juan 4
The downside is that the response to decrease the rotational speed N is slow, and if regenerative braking is added to the V power supply 2 to speed up the decrease response speed, it will be expensive, and even if regenerative braking is added, the shaft system When the inertia (GD ² ) is large, the reduction response speed is not fast enough.

[Summary of the invention]

This invention was made in order to eliminate the drawbacks of the conventional ones as described above, and the response speed is controlled by changing the output frequency F of the V power source 2 and the response speed is controlled by changing the opening degree θ of the vane 6. By comparison, we focused on the fact that the latter is faster when the air volume Q decreases and slower when the air volume Q increases, so when the load (air volume Q) increases, the frequency F of the V power supply is increased to respond, and when the load decreases, the vane first responds. To provide an inexpensive variable frequency power supply system that can quickly respond to increases and decreases in air volume Q by responding by decreasing the opening θ of the vane and then decreasing the frequency F and returning the opening θ of the vane to its original value. .

[Embodiments of the invention]

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 8, 10 is a control device, 12, 1
3 are control signals sent from the control device 10 to the V power supply 2 and the drive device 7, respectively.

FIG. 4 is an example of a logic diagram of the control device 10, where 14 is a load judger, 18 is an output signal of the load judger 14, (NOT) is a negative logic and outputs a logic signal opposite to the input, and 15 is a logic diagram of the control device 10. , 16 are selectors 1 and 2, respectively.

Next, the operation will be explained.

The load determiner 14 outputs an output signal 18 when the control signal 9 requests a load reduction, controls the selectors 2 and 16 using the output signal 18, and outputs an output signal 18 when the control signal 9 requests a load increase or there is no change. Since there is no output signal, the output signal 17 is inverted by a NOT circuit (NOT), and the selectors 1 and 15 are controlled by the output signal 17.

The selectors 1 and 15 output the control input 9 as the control signal 12 when there is a signal in the output signal 17, and when there is no signal in the output signal 17, they hold the control input 9 from before the signal disappeared and output it as the output signal 12. It operates to output.

On the other hand, when the output signal 18 has no signal, the selectors 2 and 16 output the control input 8 as the control signal 13, and the vane opening degree θ is fixed, and when the output signal 18 has a signal, the load is output from the control input 9. It operates to output a signal suitable for the vane opening degree θ required for the air volume as the control signal 13.

Since the control device 10 including the load determiner 14 and the selectors 1 and 2 operates as described above, if the load air volume control signal 9 is an increase request, the load determiner 14
Since there is no output signal 18 and the NOT outputs the output signal 17, the control signal 9 is applied to the V power supply 2 via the selectors 1 and 15 to change its output frequency F.
to follow the load. On the other hand, the control signal 9
If it is a request for a decrease, the load determiner 14 outputs an output signal 18, the selectors 2 and 16 generate the necessary control signal 13 and send it to the drive device 7, which changes the opening degree θ of the vane 6 to follow the load. . Load judger 14
The output signal 18 outputs an output for the time required for the vane 6 to follow, and then disappears, resulting in a state where there is no load change. Therefore, once the follow-up to the load reduction request is completed, the control input 9 changes to the V power supply 2. At the same time, the control signal 13 becomes the control signal 8 and returns to the original fixed value.

In the above embodiment, the fan 4 is rotated by the electric motor 3 and the air (air volume) is controlled by the vane 6, but the fan 4 may be any other rotating machine, the air may be any other fluid, or the fan 4 may be any other rotating machine. , the vane 6 may be another mechanical control mechanism, and the same effects as in the above embodiment can be achieved.

〔Effect of the invention〕

As described above, according to the present invention, when a load increase request is made to follow, the V power supply follows, and when a load reduction request is made to follow, a mechanical control mechanism such as a vane is made to follow. It is possible to sufficiently follow the load increase/decrease request without increasing the load to increase the load, and when the load increase is requested, the vane opening angle θ can be selected close to the fully open 90° compared to the case where the vane etc. are used to follow the request, resulting in energy savings. is large, and there is no need for regenerative braking to stop the speed following the reduction request, which has the effect of reducing costs.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a conventional variable frequency (V) power supply system, Fig. 2 is a diagram showing the relationship between base opening and air volume, and Fig. 3 is a block diagram of a V power supply system according to an embodiment of the present invention. FIG. 4 is an example logic diagram of the control device 10. In the figure, 2 is a variable frequency (V) power supply, 3 is an electric motor, 4 is a rotating machine, 6 is a mechanical control mechanism, θ
is the opening degree, 7 is a drive device, 10 is a control device, 8 is a control input that sets the opening degree θ to a predetermined value, 9 is a control input that provides a load request, 14 is a load determiner, 15 and 16 are selectors 1, It is 2. In addition, in the figure,
The same reference numerals indicate the same or equivalent parts.

Claims (1)

[Claims] 1. An electric motor whose rotation speed is controlled by a variable frequency power source, a rotating machine driven by this electric motor to transfer a load fluid, a mechanical control mechanism that regulates the amount of load fluid transferred by this rotating machine, and the amount of the load fluid. and a load determiner that determines whether the control signal for the load determiner is an increase request or a decrease request, and if the determination of the load determiner is an increase request, the output frequency of the variable frequency power source is increased to follow the load determiner. If the determination is that a reduction is required, the mechanical control mechanism follows the request, and then the output frequency of the variable frequency power source is lowered and the control position of the mechanical control mechanism is controlled to return to the desired position. variable frequency power supply system.