JPS62159792A - Control device of movable blade type fluid machine - Google Patents

Abstract

PURPOSE:To make operaton at a maximum efficiency point possible by changing movable blade pitch signals according to the change in loads and changing terminal voltages according to the voltage ratios of an induction motor. CONSTITUTION:A pitch signal 6a outputted from an encoder 6 is compared with a reference signal 7a to output a required voltage ratio based on a load factor. A power source circuit is formed with an igniter circuit 11 for outputting an igniter angle signal 11a based on required voltage ratio (e) and a Triac 12 for driving an induction motor IM. This makes terminal voltages applied to the induction motor change according to the change in loads to make operation of the induction motor always at a maximum efficiency point.

Description

[Detailed Description of the Invention] [Detailed Description of the Invention] [Detailed Description of the Invention] [Detailed Description of the Invention] [Detailed Description of the Invention] [Detailed Description of the Invention] [Detailed Description of the Invention] [Detailed Description of the Invention] [Detailed Description of the Invention] [Detailed Description of the Invention] [Detailed Description of the Invention] This invention relates to a movable airfoil fluid mechanical control device.

[Prior Art] Fig. 4 is a sectional view showing, for example, an axial flow blower driven by a conventional movable vane fluid machine control device. axial blower,
(2) is built into the axial blower (1), and the induction motor (I
(4) is a stationary blade fixed to the inner wall of the axial blower (1), and is arranged opposite to the movable blade (2). movable g
(2) It consists of a plurality of fan-shaped blades for rectifying the air sucked in. These movable blades (2) and stationary blades (
Although not shown, 4) is composed of a combination of multiple stages. (5) is a pitch control mechanism provided at one end of the drive shaft (3), and the pitch (angle) of each blade of movable g (2) is controlled by a hydraulic system arranged concentrically on the drive shaft (3). The amount of air discharged from movable g (2) to duct (D) is controlled by changing the air flow rate.

The conventional movable vane type fluid mechanical control device is configured as described above, and when the movable vane (2) is rotationally driven by the induction motor <IN), the air sucked in from the suction port (1a) of the axial blower (1) is is discharged from the duct (D).

This discharge air volume is controlled by a combination of movable blades 2) and stationary blades (4), and the pitch controller m(5) controls the movable blades (2).
By changing the pitch (angle) of the 6! (
1) The amount of air discharged is controlled. That is, the movable wing (
When the pitch of 2) is maximum, the scenery becomes 100%, and when the pitch is narrowed down, the air volume decreases.

In this way, the amount of air discharged from the duct (D) is controlled according to the required load, but the induction motor 1! (IN) is always operated at the rated voltage.

If a movable vane pump (not shown) is used instead of the axial blower (1) as the movable vane fluid machine, the above-mentioned effect can be achieved by changing the pitch (angle) of the pump impeller in the pump casing. Similarly, the fluid discharge amount is controlled. In this case, the axial direction is usually vertical, and the pitch control mechanism (5
Hydraulic units corresponding to ) are often mounted on the top of a hollow drive shaft.

[Problems to be Solved by the Invention] As described above, in the conventional movable vane type fluid mechanical control device, for example, when an axial flow blower (1) is used, the pitch of the movable vane (2) is reduced according to the load. This will reduce the amount of air discharged and the required power (electricity), but the induction motor (IN)
Since it is always driven at the rated voltage, the iron loss and excitation loss remain unchanged, so there was a problem that the movable airfoil fluid machine was operated with poor efficiency and poor power factor.

This invention was made to solve the above-mentioned problems, and the object is to obtain a movable airfoil fluid machine control device that can always control an induction motor with maximum efficiency regardless of fluctuations in the required load. .

[Means for Solving the Problems] A movable vane type fluid mechanical control device according to the present invention includes a pitch control mechanism that changes the pitch of the movable vane in accordance with load fluctuations, and a pitch control mechanism that changes the pitch of the movable vane in response to a pitch signal of the pitch control mechanism. The motor is equipped with a calculation section that outputs a voltage ratio corresponding to a required terminal voltage of the induction motor, and a power supply circuit that changes the terminal voltage of the induction motor in accordance with this voltage ratio.

[Operation] In this invention, the calculation unit outputs a voltage ratio according to the load at that time, and the power supply circuit applies a terminal voltage according to this □ voltage ratio to the induction motor, so that the induction motor is controlled according to load fluctuations. Always operate at the highest efficiency (minimum loss) point.

[Embodiment] Hereinafter, an embodiment of the present invention will be described with reference to the drawings, taking as an example the case where an axial flow blower is used as the movable vane type fluid machine as described above. FIG. 1 is a block diagram showing a partial circuit diagram of an embodiment of the present invention, in which (1) to (5) and (IN)
is similar to the conventional device described above. (6) is a position sensor, such as an encoder, installed in the pitch controller ti (5), and is configured to output a pi-sochi signal (6a). (7) is a preset reference signal (7
a), a reference signal generator (8) outputs a pitch signal (
6a) and the reference signal (7a) and outputs the load factor l according to the pitch of the movable g(2>), (9) is an arithmetic circuit that outputs the required voltage ratio e according to the load factor l. can be,
These comparison circuit (8) and arithmetic circuit (9) are connected to the arithmetic unit (1
0).

(11> is the firing angle signal (lla
), (12) is an induction motor (IN)
It is a triac for driving a triac (
12) is controlled by the firing angle signal (lla) so that the terminal voltage always varies according to the required voltage ratio e.

These ignition circuit 1) and triac (12) constitute a power supply circuit for the induction motor (IN).

Next, the operation of the embodiment of the invention shown in FIG. 1 will be explained with reference to the characteristic diagrams shown in FIGS. 2 and 3. Load factor 1-1, that is, when the load is maximum, the air volume is 100
%, the movable blade (2) in the axial blower (1) is driven by an induction motor (IN) at the rated voltage, and the movable blade (2)
The pitch is fully open, that is, the angle is maximum (in this case, around 60 degrees), and the required power at that time is approximately 100% (see Figure 2).

When the load factor p1, that is, the load decreases, the pitch control mechanism (5) operates according to the load, and the pitch of the movable blade (2) is narrowed to limit the amount of air discharged into the duct (D). be done. At this time, the position sensor (6) sends the current pitch signal (6a) to one input terminal of the comparator circuit (8). Since a preset reference signal (7a) (for example, a signal corresponding to the maximum pitch) is input to the other input terminal of the comparison circuit (8), the pitch signal (6a) is different from the reference signal (7a). A comparison calculation is performed, and a load factor of 1 (0<ffi<1) corresponding to the pitch signal (6a) is output.

FIG. 2 is a characteristic diagram showing the relationship between the air volume and required power, which is the basis of the reference signal (7a). Normally, the rated output of the induction motor (IN) is 10 to 2 times the required power of the axial blower (1).
Since it has a margin of 0%, if you calculate the rated output in advance by multiplying the characteristic curve in Figure 2 by the margin, you can easily find the current load factor l from the pitch signal (6a). .

The arithmetic circuit (9) determines the reference voltage (voltage ratio e=1) by determining the minimum input voltage at the rated load (l=1>), and calculates the required terminal voltage ratio e based on the current load factor I. In general, if the voltage ratio expressed with the reference voltage as 1 is e, and the load factor expressed as the full load (maximum load) is 1, then the loss WT of the induction motor (IN) is as follows: Wy=W+ao+ Wco -e 2+ 3r+
(Izo) 2e-21'+3r+(I cut o) 2e2
+3rz(Izo)2e-212... ■However, W m o : Mechanical loss at reference voltage (voltage ratio e=1) Wco: Iron loss at reference voltage ■2゜: Secondary current at reference voltage Imo: Rated load Excitation current r1 at (load factor: 1=1) resistance value of the secondary winding rz: resistance value of the secondary winding. In equation (2), the first term is mechanical loss, the second term is iron loss, the third and fourth terms are primary copper loss, and the fifth term is secondary copper loss. Since the equation (2) is a downwardly convex function curve with respect to the voltage ratio e, by differentiating the equation (2) with respect to the voltage ratio e, the minimum point, that is, the point where the loss WT is minimized, can be found.

Therefore, θWr/θe=2eWco-6r1(12o)"e-J
! 2+6r+(Imo)2e+6r2(12o)2e-
12-2e[Wco+ 3r+ (Imo>23(r,
+ rz＞・(12o)2e−'12] Find the condition that aWT/θe=o from ``'■.Now, at the rated load (l=1), the input current is minimum, that is, the loss WT
Assuming that the voltage at which is the minimum is found, use this voltage as the reference (
Let e=1>. To find the reference voltage (voltage ratio e-1), for example, connect an induction motor (IM) to an axial blower (1), drive it to the rated load (1 = 1), and maintain this state. The voltage at which the input current is minimum can be detected by varying the voltage. At this point θWT/θ
In order for e辷O to hold true, from formula ■, Wco+3r, (Imo)”#3(rl+r2)・(1
2o) 2-■, and it can be seen that equation 0 is not related to the load factor r.

In addition, in order for the 0 formula to hold even for a load below the rated load (1 < 1 >), e-'12=1,',e-'1=1...■.From the 0 formula, the terminal The voltage ratio e is the square of the load factor l □1
1. It can be seen that by changing it in proportion to the root, the induction motor (IN) is always operated at the maximum efficiency point at any load factor l.

In this way, the arithmetic circuit (9) determines the required terminal voltage ratio e from the relationship e=ZO, S, and outputs it to the ignition circuit 11).

The ignition circuit (11) generates a ignition angle signal (l1m) and controls the ignition angle of the triac (12) so that the terminal voltage of the induction motor (IN) becomes a required voltage ratio e.

Figure 3 is a characteristic diagram showing the relationship between load factor l and loss WT when using a 500KW, 4P (4 pole) induction motor (IN) with a 3.3KV, 60IIz power supply, for example. Curve A shows the case of driving at the conventional rated voltage, and curve B shows the case of driving by changing the voltage ratio e according to the present invention. In general, commercially available induction motors do not have the minimum loss for the rated load (1 = 1) even when driven at the rated voltage, but as mentioned above, the terminal voltage ratio e at which the input is minimum at the rated load By determining and correcting (curve B) j! Even when =1, the loss W7 can be minimized. Furthermore, by decreasing the voltage ratio e as the load factor a decreases, the loss is significantly reduced, especially in the light load region, compared to conventional operation (curve A) where the efficiency and power factor decrease as the load factor l decreases. WT can be improved.

The configuration of the movable airfoil fluid machine control device according to the present invention described above is different from the conventional device by adding only a calculation section (10) and a power supply circuit consisting of an ignition circuit (11) and a triac (12). Therefore, it can be easily implemented by adding it to existing equipment.

In the above embodiment, the axial flow blower fi(1) is used as an example of the movable vane type fluid machine, but the movable vane type fluid machine 31E ( The main structure and principle are the same except that the pitch signal (6a) in 2) is replaced with the pitch signal of the impeller.

Further, although the triac (12) is used as the element of the power supply circuit of the induction motor (114), it goes without saying that the same effect can be obtained by using other elements such as a thyristor.

[Effects of the Invention] As described above, according to the present invention, there is provided a pitch control mechanism that changes the pitch of the movable blades in accordance with load fluctuations, and a pitch control mechanism that changes the required terminal voltage of the induction motor in accordance with the pitch signal of this pitch control mechanism. A calculation unit that outputs a corresponding voltage ratio and a power supply circuit that changes the terminal voltage of the induction motor according to this voltage ratio are provided, and the terminal voltage applied to the induction motor is changed according to load fluctuations. Therefore, the induction motor can always be operated at the highest efficiency (minimum loss) point, and the power factor can be maintained almost the same as the rated point, contributing to energy savings and
This has the effect of providing a movable airfoil fluid mechanical control device that can lower the input KV^ (apparent input power) during light loads.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing a partial circuit diagram of an embodiment of the present invention, FIG. 2 is a characteristic diagram showing the relationship between air volume and required power,
FIG. 3 is a characteristic diagram showing the relationship between load factor and induction motor loss, and FIG. 4 is a sectional view showing an axial flow blower as a conventional movable vane type fluid machine. (1)... Axial flow If! (IN)...Induction motor (2)...Movable blade (6a)...Pitch signal (7a)...Reference signal (8)...Comparison circuit (9)...Arithmetic circuit (10 )...Arithmetic unit (11)...Ignition circuit (lla)...Ignition angle signal (12)...Triac l...Load factor e
. . . Voltage ratio. In the figures, the same reference numerals indicate the same or equivalent parts. −ξl(1+a7p?

Claims (7)

[Claims] (1) An induction motor that rotationally drives a movable blade of a movable vane type fluid machine, a pitch control mechanism that changes the pitch of the movable blade according to load fluctuations, and an induction motor that changes the pitch of the movable blade according to a change in load, and A movable airfoil fluid machine comprising: a calculation unit that outputs a voltage ratio corresponding to a required terminal voltage of an electric motor; and a power supply circuit that changes the terminal voltage of the induction motor according to the voltage ratio. Control device. (2) The movable vane fluid machine control device according to claim 1, wherein the movable vane fluid machine is an axial blower. (3) The movable vane fluid machine control device according to claim 1, wherein the movable vane fluid machine is a movable vane pump. (4) The arithmetic unit comprises a comparison circuit that compares a reference signal and a pitch signal and outputs a load factor, and an arithmetic circuit that calculates a voltage ratio from the load factor. The movable airfoil fluid mechanical control device according to any one of items 1 to 3. (5) The movable airfoil fluid machine control device according to claim 4, wherein the arithmetic circuit outputs a voltage ratio proportional to the square root of the load factor. (6) The power supply circuit includes an ignition circuit that outputs a ignition angle signal according to the voltage ratio, and a triac that is controlled by the ignition angle signal so that the terminal voltage becomes a value corresponding to the voltage ratio. A movable airfoil fluid machine control device according to any one of claims 1 to 5. (7) The power supply circuit includes a firing circuit that outputs a firing angle signal according to the voltage ratio, and a thyristor that is controlled by the firing angle signal so that the terminal voltage becomes a value corresponding to the voltage ratio. A movable airfoil fluid machine control device according to any one of claims 1 to 5.