JPS637193A - Exhaust fan driver - Google Patents

Abstract

PURPOSE:To most efficiently exhaust flue gas free of overload on a driving motor and an inverter at the time of low temperature initially of generating gas by providing an upper limit command calculator. CONSTITUTION:Temperature in a flue gas duct 7 is detected from a temperature sensor 9 attached to a suction port 7a, and the current of an induction motor 4 is detected by a current transformer 10. An upper limit command calculator 11 calculates the upper limit speed on the basis of a detection signal from the sensor 9 and the transformer 10, and outputs an upper limit frequency operation command to an inverter 3 due to the calculated result. In other words, the operation that the gas temperature rises from low to high is valve executed in the most efficient state free of overload state.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an exhaust fan drive device used in an exhaust duct where temperature changes are large.

[Conventional technology]

FIG. 3 is a schematic diagram showing a conventional exhaust fan drive device. In the figure, 1 is a commercial power supply, 2 is an input breaker, 3 is a variable voltage variable frequency power supply device (hereinafter abbreviated as an inverter device), and 4 is a schematic diagram showing a conventional exhaust fan drive device. 5 is an induction motor as a driving motor, 5 is an exhaust fan, 6 is a gas generation source such as a process device, 7 is an exhaust duct, 7a is an intake port, 7b is an exhaust port, and 8 is a smoke exhaust.

Next, the operation will be explained. When gas is generated from the gas generation source 6, the inverter device 3 starts operating, and the induction motor 4 rotates the exhaust fan 5. As a result, the gas is discharged from the exhaust lower a as flue gas 8. The air volume inside the exhaust duct 7 at this time is determined by the rotation speed of the exhaust fan 5, but this rotation speed can be changed by frequency control of the inverter device 3.

[Problem that the invention seeks to solve]

Since the conventional exhaust fan drive device is configured as described above, it has the following problems caused by temperature changes inside the exhaust duct 7.

That is, if the shaft power of the induction motor 4 is P, this shaft power P is given by: Here, K is a proportional constant, No is the rated rotation speed, N is the rotation speed during operation, T is the reference temperature, and T2 is the temperature during operation. As is clear from this equation, T2 is T
If it is smaller than 1, the shaft power P will also increase accordingly. In other words, the gas from the gas source 6 is
At the beginning of the occurrence, the gas temperature is low, so if there is not enough capacity in the inverter device 3 and induction motor 4, these devices will be in an overload state. Therefore, when selecting these devices, it is necessary to select ones with a larger capacity rating than that required during normal operation, which increases the size of the equipment and makes it disadvantageous in terms of price. There was a problem with that.

This invention was made to solve the above-mentioned problems, and it is possible to efficiently exhaust air when the inside of the exhaust duct is low temperature without increasing the capacity of the inverter device and drive motor. An object of the present invention is to provide an exhaust fan drive device.

[Means for solving problems]

The exhaust fan drive device according to the present invention detects the temperature inside the exhaust duct and the current of the drive motor, and determines the upper limit rotation allowed at that time from these detected values and the shaft power characteristic curve of the drive motor. A number is calculated and the inverter device is operated based on the result of the calculation.

[Effect]

The upper limit command calculation device in the present invention outputs an operation command to the inverter device so that the drive motor and the inverter device are not overloaded and the most efficient exhaust is performed at a low temperature when gas is first generated.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings. 1st
In the figure, 9 is a temperature sensor attached to the intake lower a, 10 is a current transformer as a current detection means for detecting the current of the induction motor 4, and 11 is a temperature sensor that detects the current from the temperature sensor 9 and the current transformer 10. This is an upper limit command calculation device that calculates the upper limit rotation speed and outputs an upper limit frequency operation command based on the calculation result to the inverter device 3.

Next, the operation will be explained. -Generally, when controlling the rotation speed of an electric motor, considering that the cooling characteristics of the motor itself change due to changing the rotation speed, the allowable shaft power of the motor is approximately the square of the rotation speed. is proportional to. Therefore, also for the induction motor 4 of this embodiment, the characteristic curve regarding the allowable shaft power is 2 as shown by the curve Z in FIG.
It becomes like the following curve.

On the other hand, the actual shaft power P when the induction motor 4 is operated,
As is clear from the above equation, it is proportional to the cube of the rotation speed, so its characteristic curve is curve A (T3
), A(T, ) is a cubic curve.

Here, curve A (TI) shows the case where the exhaust process has started up to a normal state and its gas salt T3 is high;
(Tt) indicates the case where the gas salt T4 at the start of the exhaust process is low. Then, as the gas salt gradually increases from T to T4, the characteristic curve of the actual shaft power P also changes from curve A (
T4. ) gradually shifts to curve A (T3). Note that the 100% position on the horizontal and vertical axes in FIG. 2 indicates the rated state of the induction motor 4.

For example, when trying to rotate the induction motor 4 in the state of gas salt T4, the rotation speed N is determined by the curve Z and the curve A.
(Tt) must be limited to or less than the upper limit rotation speed N corresponding to the intersection m. This is because if the rotational speed exceeds the upper limit rotation speed N5 under gas salt T4, the shaft power Pr will exceed the allowable shaft power. The upper limit command calculation device 11 in FIG. . and,
An upper limit frequency operation command corresponding to this upper limit rotation speed N is output to the inverter device 3.

Furthermore, if the exhaust continues for a while in this state, the gas temperature T4 will gradually rise. Then, along with this, the positions of the intersection point m and the upper limit rotation speed N gradually move to the right, and finally match the rated state. In other words, the operation until the gas temperature rises from T4 to T is performed in the most efficient state without becoming overloaded.

Note that although the upper limit command calculation device 11 limits the inverter device 3 using the upper limit frequency, if there is sufficient current in the induction motor 4, correction can be made using the current value.

〔Effect of the invention〕

As described above, according to the present invention, the drive motor is configured to operate at the upper limit rotation speed determined by its shaft power characteristic curve, so that the inverter device and the drive motor capacity are not increased. This has the effect that exhaust can be carried out most efficiently when the inside of the exhaust duct is at a low temperature.

[Brief explanation of drawings]

Fig. 1 is a schematic configuration diagram showing an exhaust fan drive device according to an embodiment of the present invention, Fig. 2 is a characteristic diagram showing the relationship between shaft power and rotation speed of the induction motor of Fig. 1, and Fig. 3 is a conventional 1 is a schematic configuration diagram showing an exhaust fan drive device of FIG. 3 is an inverter device, 4 is an induction motor (drive motor),
5 is an exhaust fan, 6 is a gas generation source, 7 is an exhaust duct,
9 is a temperature sensor, 10 is a current transformer (current detection means), 11
is an upper limit command calculation device. In addition, in the figures, the same reference numerals indicate the same or equivalent parts. n dimension] 0■

Claims (1)

[Claims] An exhaust fan drive device including a drive motor for driving an exhaust fan disposed inside the exhaust duct, and an inverter device for inverter operation of the drive motor, comprising: a temperature sensor installed inside the exhaust duct; , is determined by a shaft power characteristic curve of the drive motor based on a current detection means attached to the output side of the inverter device and detects the current flowing to the drive motor, and detection signals from the temperature sensor and the current detection means. An exhaust fan drive device comprising: an upper limit command calculation device that calculates an upper limit rotation speed and outputs an upper limit frequency operation command based on the calculation result to the inverter device.