JPH03243192A - Control method for induction motor - Google Patents

Abstract

PURPOSE:To suppress the deterioration in the amount of flowing air by a method wherein the phase of an induction motor is controlled upon the reduction of the load of a fan so that an impressing voltage on the induction motor is returned to the impressing voltage upon the maximum load before the reduction of the load. CONSTITUTION:When a voltage impressed on an indoor fan motor 1 is smaller than a voltage, under which the indoor fan is rotated with a set value under the maximum load, it means that the load of the indoor fan is small due to dewing of a heat exchanger of an indoor machine side, the change of the direction of an air deflecting plate or the like. Then, the voltage (V) impressed on the indoor fan 1 is compared with the voltage (VNset), under which the indoor fan is rotated with a set value under the maximum load, and when the voltage V is not smaller than the voltage VNset, the indoor fan is being operated under the condition of the maximum load. When the voltage V is smaller than the voltage VNset, the indoor fan is being operated under a condition that the load thereof is small. Then, the phase of the voltage V impressed on the indoor fan 1 is controlled so that it approaches the voltage VNset.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for controlling an induction motor used in a fan motor of an air conditioner, etc., and more specifically, to a control method for preventing a decrease in air volume during load fluctuations. Regarding the method.

[Conventional technology]

Microcomputers are used to control air conditioners, and they now have a variety of functions. Among them, an induction motor is used for the indoor fan motor, and the rotation of this induction motor is controlled by a phase control method. It looks like this.

For phase control, the pulses generated by the rotation of the induction motor are counted at fixed intervals (seconds), and this count value is converted to the number of rotations, and this converted number of rotations is compared with a set value. At the same time, the conduction angle of the induction motor is changed by a predetermined amount in accordance with the comparison result, and the rotation speed of the induction motor is gradually brought closer to the set value, and is stabilized at the rotation speed of the set value. It looks like this.

[Problem to be solved by the invention]

However, with the conventional rotation speed control method as described above, for example, dew may form on the heat exchanger on the indoor unit side, the air flow may deteriorate due to changes in the direction of the wind direction plate, etc., and the load on the fan may become light. Since the rotation speed is controlled to be kept constant even when
As a result, the heat exchange efficiency of the indoor heat exchanger decreases, making it impossible to fully demonstrate its ability as an air conditioner.

Therefore, an object of the present invention is to provide an induction motor control method that can solve these problems and suppress a decrease in air volume even when the fan load decreases.

(Means for Solving the Problems) The present invention has been made to solve the above problems, and when controlling the rotation speed of an induction motor equipped with a fan, it is possible to control the pulses generated by the rotation of the induction motor. The induction motor counts at predetermined time intervals, detects the rotation speed of the induction motor from the counted value, compares the detected rotation speed with a set value, and performs phase control of the rotation speed of the induction motor in stages. In the control method, when the load on the fan decreases, phase control is performed so that the voltage applied to the induction motor returns to the voltage applied at the maximum load before the load decrease.

[Effect]

With the above configuration, even if the load on the fan decreases, the voltage applied to the induction motor does not decrease, so the number of rotations of the fan increases, and a decrease in air volume can be prevented.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on FIGS. 1 and 2.

In FIG. 1, this air conditioner includes an indoor fan motor (induction motor) 1 for circulating cool air or warm air indoors, a motor drive section 2 that drives the indoor fan motor 1, and a motor drive section 2 for driving the indoor fan motor 1. A controller (microcomputer) 3 is provided to control the indoor fan motor 1 via the controller 2 .

Note that the control unit 3 outputs a trigger pulse to the motor drive unit 2 via an output boat in order to drive the indoor fan motor 1 in response to an instruction from a remote control or the like (not shown), and
In order to detect the rotation speed of the indoor fan motor 1, pulses generated by the Hall element provided in the indoor fan motor 1 are inputted via the input port, and the rotation speed of the indoor fan motor 1 is
Controls the rotation speed to the set value.

Although not shown, the air conditioner is also provided with an indoor temperature sensor, other sensors, a compressor, a refrigeration cycle including a four-way valve, and the like.

Further, the motor drive section 2 is provided with a triunk 5 that applies a conduction frequency of the AC power source 4 to the indoor fan motor 1 using a trigger pulse outputted from an output port of the control section 3 .

The control unit 3 is equipped with a memory that stores a program for controlling the rotation speed of the indoor fan motor 1 to a set value, a control program shown in FIG. 2, and the like.

Next, a method for controlling the indoor fan motor l applied to the air conditioner having the above configuration will be explained based on the flowchart shown in FIG.

First, when the air conditioner is started, a predetermined trigger pulse is output from the output port of the control unit 3, and the indoor fan motor l rotates at a set value (set rotation speed) Nset when the indoor fan motor is at its maximum load. A voltage V N5et is applied, and the indoor fan motor l starts rotating (step 5T1),
Pulses generated by the rotation are input to the input port of the control unit 3.

In step ST2, the pulses generated as the indoor fan motor l rotates are counted at fixed time intervals (seconds), and this count value is converted into the rotational speed n and detected.

In step ST3, this converted rotation speed n and the set value N5et
are compared to see if they are equal, and if they are equal, the process returns to step ST2.

If the comparison results in step ST3 are not equal, the process proceeds to step ST4, and in step ST4, it is compared whether the converted rotation speed n is larger than the set value N set, and if the converted rotation speed n is smaller than the set value N set. The process proceeds to step ST5.

In step ST5, the applied voltage V is increased by changing (increasing) the conduction angle of the indoor fan motor 1 by a predetermined amount, and the rotation speed n of the indoor fan motor 1 is set to a set value N5e.
The control is repeated until the value becomes approximately equal to t.

Further, as a result of the comparison in step ST4, if the converted rotation speed n of the fan motor 1 is larger than the set value N5et, the process proceeds to step ST6, and in this step ST6, the conduction angle of the indoor fan motor 1 is changed by a predetermined amount ( By decreasing the applied voltage V, the rotation speed n of the indoor fan motor 1 approaches the set value N5et.

If, at this time, the voltage V applied to the indoor fan motor 1 is smaller than the voltage V N5eL at which the indoor fan rotates at the set value N5et at maximum load, this is due to the heat exchanger on the indoor unit side. This means that the load on the indoor fan has decreased due to dew buildup on the indoor fan or a change in the direction of the wind direction plate.

Therefore, in step ST7, the voltage V applied to the indoor fan motor 1 and the set value N5 at the maximum indoor fan load are determined.
The rotation voltage VN5et is compared with the voltage VN5et, and if the voltage V is not smaller than the voltage VNset, it means that the indoor fan motor 1 is being operated under the maximum load condition.
The process returns to step ST2.

In the comparison in step ST7, the voltage V is the voltage V N
If it is smaller than 5et, it means that the indoor fan motor 1 is being operated under a small load condition, and the process proceeds to step ST8.

In step ST8, the phase of the voltage V applied to the indoor fan motor 1 is controlled until it approaches the voltage V N5et described above.

In this way, when the indoor fan motor 1 is operated under a small load condition, the rotation speed of the indoor fan motor 1 is increased by bringing the voltage V applied to the indoor fan motor l closer to the voltage VN5et. This makes it possible to prevent a decrease in heat exchange capacity due to a decrease in load.

〔Effect of the invention〕

If the air conditioner uses the induction motor control method described above, dew may form on the heat exchanger on the indoor unit side, or the load on the fan motor may be light due to the direction of the wind direction control board, etc. In such a case, the rotation speed of the fan motor can be automatically increased to obtain a predetermined air volume, which prevents deterioration of heat exchange performance and provides comfortable air conditioning.

[Brief explanation of drawings]

FIG. 1 is a block diagram of essential parts of an air conditioner to which an embodiment of the induction motor control method of the present invention is applied, and FIG. 2 is a flowchart for explaining the above control method. In the figure, 1---- Single indoor fan motor (induction motor),
2-motor drive unit, 3-control unit, 4-AC power supply, 5-1
Liatsk. Figure 1

Claims (1)

[Claims] When controlling the rotation speed of an induction motor equipped with a fan, the pulses generated by the rotation of the induction motor are counted at predetermined time intervals, and the rotation speed of the induction motor is detected from this count value. In the induction motor control method, the rotational speed of the induction motor is phase-controlled in stages by comparing the rotation speed with a set value, and when the load of the fan is reduced, the voltage applied to the induction motor is set to the maximum load before the load reduction. 1. A method for controlling an induction motor, characterized in that the phase is controlled so as to return the applied voltage to the applied voltage.