JPH0236020Y2 - - Google Patents

Description

[Detailed description of the invention] (Field of industrial application) The invention is an air conditioner, specifically a cooling evaporator equipped with a fan driven by a motor connected to a frequency converter and whose rotation speed can be controlled. The present invention relates to an air conditioner equipped with a user-side heat exchanger.

(Prior Art) This type of air conditioner is used for the purpose of energy saving, and is already known as described in, for example, Japanese Utility Model Application Publication No. 55-168132.

However, in the air conditioner, as the load on the air-conditioned room decreases when performing cooling operation, the rotation speed of the fan motor attached to the heat exchanger on the user side also decreases. In this case, the amount of air supplied to the heat exchanger was insufficient, and the evaporation of the low-pressure liquid refrigerant was extremely suppressed, causing the compressor to start up and damaging the liquid compression in the compressor.

(Purpose of the invention) The present invention was devised in view of this conventional problem, and the main first purpose is to connect a lower limiter circuit to the frequency converter to regulate the minimum output frequency of the converter, and to By making the capacity of the fan variable according to the load of the air-conditioned room, etc.,
Moreover, the minimum air volume of the fan can be set to an appropriate value without causing liquid compression in the compressor.

Furthermore, the second purpose is to avoid the possibility that if the lower limit setting signal voltage output from the limiter circuit is applied to the motor all at once at the same time as the air conditioner starts operating, a large starting current will flow through the motor and damage the motor. In order to prevent the occurrence of this excessive starting current, the signal voltage output from the limiter circuit is gradually increased from zero voltage to the lower limit setting signal voltage at the start of operation.

(Structure of the invention) The structure of the invention is that ducts 6 and 61 are connected to an air conditioner 4 equipped with a fan 2 and a heat exchanger 3, and air conditioning is provided to multiple rooms 7 via the ducts 6 and 61. In an air conditioner that supplies air,
A frequency converter 10 is connected to the motor 1 of the fan 2 so that the rotation speed of the motor 1 can be controlled.
A first setting circuit 14 is provided with a static pressure detection unit 11 that detects static pressure within 1, and a first setting circuit 14 that sets a minimum control static pressure.
a second setting circuit 15 that sets a maximum control static pressure corresponding to the maximum rotation of the motor 1; and a second setting circuit 15 that sets a maximum control static pressure corresponding to the maximum rotation of the motor 1; 6 and 61, the control static pressure setting device 12 includes a calculation circuit 17 for calculating the necessary control static pressure, and the static pressure detection unit 11
The detected static pressure is compared with the control static pressure set by the setting device 12, a frequency setting signal corresponding to the control static pressure that matches the detected static pressure is calculated, and the setting signal is applied to the frequency converter 10. A controller 13 is provided for outputting an output to the power supply, and a lower limiter circuit is provided for the power supply, which is made up of a series circuit in which a first resistor and a parallel circuit of a second resistor and a capacitor are connected in series. A connection point between the first resistor and the parallel circuit and the output side of the controller are connected via a pair of diodes with cathodes facing each other, and a connection point of these diodes is connected to the frequency converter. The number of revolutions of the motor is controlled by a control static pressure according to the amount of air blown, and the power supply voltage is divided by the first and second resistors, and the lower limit setting signal voltage is arbitrarily set by the second resistor. In addition, due to the so-called diode OR circuit formed by the interposition of the pair of diodes, the voltage at the connection point of the two diodes does not drop below the lower limit setting signal voltage set as described above during steady operation of the fan, and the fan While a lower limit is set for the rotation speed, that is, a lower limit is set for the fan air volume, by appropriately selecting a time constant determined by the capacitor and the second resistor, the lower limit setting signal voltage can be changed from zero voltage according to the time constant. This was achieved by gradually increasing the pressure.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

What is shown in FIG. 1 is an air conditioner according to an embodiment of the present invention, which includes an air conditioner 4 having a fan 2 rotated by a motor 1 and a heat exchanger 3 on the user side, that is, the indoor side. A main duct 6 having a plurality of branch ducts 61 is connected to the conditioned air outlet 5 in the main duct 4, and conditioned air is supplied to the plurality of rooms 7 through the ducts 6, 61. still,
Although not shown, the air conditioner includes a heat exchanger on the heat source side, that is, on the outdoor side, an expansion mechanism, and a compressor, together with the air conditioner.
A refrigerant circuit is formed by the outdoor heat exchanger, the expansion mechanism, and the indoor heat exchanger. Furthermore, a terminal unit 8 is connected to the end of the branch duct 61 for adjusting the volume of conditioned air supplied to each room 7, respectively.

This terminal unit 8 is a throttle type equipped with a damper 9 having a static pressure adjustment mechanism, and if the static pressure on the inlet side of the unit 8 is equal to or higher than the minimum static pressure P ₁ for the static pressure adjustment mechanism to operate. By setting the opening degree of the damper 9, the supplied air volume can be controlled to a constant air volume according to the opening degree of the damper 9, regardless of the static pressure on the inlet side.

In the air conditioner constructed as described above, the rotation speed of the motor 1 of the fan 2 is adjusted according to the amount of air supplied from the ducts 6 and 61, as shown in FIGS. As schematically shown, firstly, a frequency converter 10 is connected to the motor 1 so that the number of rotations of the motor 1 can be controlled to increase or decrease continuously, and secondly, the frequency converter 10 is connected to the motor 1 so that the rotation speed of the motor 1 can be controlled to increase or decrease continuously.
The position Z before branching in the branch duct 61
At position Z before connection, the static pressure Pd in the main duct 6
Thirdly, a first setting circuit 14 that sets a minimum control static pressure in the ducts 6, 61 and a maximum control static pressure corresponding to the maximum rotation of the motor 1 are provided. a second setting circuit 15,
Within the range of the minimum control static pressure and the maximum control static pressure,
and a control static pressure setter 12 including an arithmetic circuit 17 that calculates a necessary control static pressure in the ducts 6 and 61 with respect to the supplied air volume; a static pressure detected by the static pressure detection unit 11; a controller 13 that compares the control static pressure set by the setting device 12, calculates a frequency setting signal corresponding to the control static pressure that matches the detected static pressure, and outputs the setting signal to the frequency converter 10; and

In this way, the static pressure Pd at the position Z in the main duct 6 changes to the control static pressure Ps (necessary This is done so that the static pressure can be controlled.

Furthermore, in order to prevent liquid compression in the compressor, a lower limit limiter circuit sets a lower limit of the signal voltage input to the frequency converter 10 to set the minimum rotation speed of the fan 2 during operation of the air conditioner. 29 is connected to the frequency converter 10 in parallel with the controller 13.

Note that 30 is a rotational abnormality detection circuit that detects rotational abnormality such as stoppage of the fan 2 using the detected static pressure.

Next, a method of setting the control static pressure Ps based on the frequency setting signal V input to the frequency converter 10 in the setting device 12 will be described.

The control static pressure Ps at the position Z where the detection section 11 of the main duct 6 is provided is the necessary static pressure _P1 at the terminal unit 8 and the duct 6,
The control static pressure must be greater than the sum (required minimum static pressure) of the pipe resistance of the outlet side portion with respect to the mounting position Z of the detection unit 11 in 61 (solid line c in Figure 4). pressure
As shown by the solid line D in Figure 4, Ps is the supply air volume Q
It is set so that it changes linearly. In other words, when the supply air volume Q is almost zero, the control static pressure
Let Ps be _P1 , and let P be the pipe resistance of the outlet side portion of the ducts 6, 61 at the position Z when the air volume Q is maximum, that is, when the rotation speed of the motor 1 is maximum, The control static pressure Ps at this maximum air volume Qmax is set to P ₃ (=P ₁ +P ₂ ), and the control static pressure Ps is made to change linearly with respect to the supply air volume Q. That is, the control static pressure
Ps is set in the relationship Ps=Q/Qmax·P ₂ +P ₁ .

On the other hand, since the supply air volume Q is in a proportional relationship with the rotation speed of the fan 2, the frequency setting signal V (or the output frequency output from the converter 10), which is in a proportional relationship with the duct of the motor 1, and the control static As shown in Figure 5, between the pressure Ps and Ps
The relationship V/Vmax·P ₂ +P ₁ holds, and therefore, the control static pressure Ps can be set from the frequency setting signal V without directly detecting the supply air volume Q. Note that Vmax is the maximum frequency setting signal corresponding to the maximum air volume Qmax.

Further, FIG. 6 shows that the frequency setting signal V and the output frequency are in a proportional relationship.

Next, the electronic circuits constituting the setting device 12, the controller 13, the lower limiter circuit 29, etc. will be explained based on FIG.

The setting device 12 includes first and second setting circuits 14 that respectively set the initial conditions of the control static pressure Ps, that is, the minimum control static pressure P ₁ and the maximum control static P ₃ (P ₃ =P ₁ +P ₂ ). 15 Third setting circuit 16 that sets the maximum frequency setting signal Vmax (maximum rotation speed of the motor 1) These first to third setting circuits 14, 15, 16
an arithmetic circuit 17 that inputs the signal voltage from the controller 13 and the frequency setting signal V of the controller 13 and calculates V/Vmax·P ₂ +P ₁ (=Ps) in order to calculate the control static pressure Ps; and an initial value detection circuit 18 for detecting the maximum control static pressure _P3 to be set by the second setting circuit 15.
It consists of

To further explain the electronic circuit in detail, the first setting circuit 14 connects fixed resistors R ₆ to _{R 10} in series to the power supply, and also includes a variable resistor that adjustably sets the minimum control static pressure P _{1 .} R _v1 is connected in parallel to the resistor R ₆ .

Similarly to the first setting circuit 14, the second setting circuit 15 also includes fixed resistors R ₁ to R ₅ connected in series to the power supply, and a variable resistor R that adjustably sets the maximum control static pressure P ₃ . _v2 is connected in parallel to the resistor _R3 . Note that C ₀ is a capacitor.

The third setting circuit 16 includes a fixed resistor _R27 and a variable resistor that sets the maximum frequency setting signal Vmax.
It consists of a series circuit with R _v3 and a fixed resistor R ₂₆ .

The arithmetic circuit 17 includes a subtraction circuit 19 that subtracts the minimum control static pressure P ₁ from the maximum control static pressure P ₃ to calculate the maximum pipe resistance P 2 , an inversion circuit 20 that inverts the frequency setting signal V, and a subtraction circuit 19 that calculates the maximum pipe resistance P ₂ by subtracting the minimum control static pressure P 1 from the maximum control static pressure P 3 ; Setting signal
Vmax, a multiplication/division circuit 21 for calculating -V/Vmax·P ₂ from the frequency setting signal V and the maximum pipe resistance P ₂ , an inverting circuit 22 , and a It consists of an adder circuit 23 that adds the inverted output signal of the multiplier/divider circuit 21 and the signal of the minimum control static pressure P ₁ to calculate the control static pressure (Ps=V/Vmax·P ₂ +P ₁ ).

In addition, A ₁ to _{A 6} shown in the arithmetic circuit are operational amplifiers, R ₁₁ to _{R 34} are fixed resistors, C ₁ to C ₇ are capacitors,
_D1 is a diode and FET is a field effect transistor.

Further, the initial value detection circuit 18 normally detects the static pressure inside the ducts 6, 61 when the capacity of the motor 1 of the fan 2 is such that the motor 1 rotates at maximum speed and the maximum air volume is supplied from the ducts 6, 61. Noting that P 3 is designed to be the required (minimum) static pressure, the motor 1 is actually rotated to the maximum, and the maximum control static pressure P ₃ set by the second setting circuit 15 at this time is and the detected static pressure Pd are directly compared, and the _difference between these static pressures is displayed. A comparison circuit that compares the detected static pressure Pd detected by the pressure detection unit 11 and outputs a comparison signal, that is, an H signal when the maximum control static pressure _P3 is larger than the detected static pressure Pd, and an L signal when the opposite is the case. 24, and a switch circuit 2 that is turned on and off by the H or L signal output from the comparison circuit 24.
5, and a light emitting diode that emits light when the switch circuit 25 is turned on, that is, emits light when the maximum control static pressure _P3 is greater than the detected static pressure Pd.
Consists of LEDs.

In addition, A ₁₀ is an operational amplifier, R ₃₅ to _{R 41} are fixed resistors,
C ₁₂ to _{C 13} are capacitors, T _r1 is an NPN transistor, and D ₁ is a diode.

Next, the controller 13 will be explained. The controller 13
is the control static pressure Ps output from the setting device 12
and a signal of the detected static pressure Pd output from the static pressure detection section 11, and a subtraction circuit 26 which outputs the differential pressure Pd-Ps between these static pressures Ps and Pd, and the signal of the subtraction circuit 26. It consists of an integrating circuit 27 that integrates the voltage and calculates -1/C ₉ R ₄₅ ∫ (Pd - Ps) dt, and an inverting circuit 28 that inverts the signal voltage of the circuit 27. The differential pressure between the control static pressure Ps and the control static pressure Ps is integrated, and the integrated signal is used to output a frequency setting signal V to the frequency converter 10 so that the detected static pressure Pd matches the control static pressure Ps. ing.

In addition, in the controller 13, A ₇ to _{A 9} are operational amplifiers, and R ₄₂
~ _R47 is a fixed resistor, TR is a variable resistor, _C8 ~ _C11 is a capacitor, ZD is a constant voltage diode, and _D2 is a diode.

Next, the lower limiter circuit 29, which has an important meaning in the present invention, has a first resistor _R48 connected to the power supply.
and a parallel circuit of a second resistor R ₄₉ and a capacitor C ₁₁ are connected in series, and further, a connection point between the first resistor R ₄₈ and the parallel circuit in this limiter circuit 29, The output side of the controller 13 is connected to a pair of diodes D ₄ , each with its cathode facing the other.
D ₅ and these diodes D ₄ ,
The connection point _D5 is connected to the frequency converter 10.

The limiter circuit 29 divides the power supply voltage by the first and second resistors R ₄₈ and R ₄₉ , and the second resistor R ₄₉ divides the lower limit setting signal voltage output from this circuit 29, that is, the lower limit frequency. Setting signal Vlim
can be set arbitrarily, and a so-called diode formed by interposing the pair of diodes.
Due to the OR circuit, during steady operation of the fan, the voltage at the connection point between the two diodes does not drop below the lower limit setting signal voltage set as described above, and a lower limit is set for the rotation speed of the fan, that is, a lower limit is set for the fan air volume. On the other hand, by connecting a capacitor _C11 in parallel with the second resistor _R49 and in series with the first resistor _R48 , even when the power is turned on, the output of the lower limiter circuit 29 is The signal voltage does not rise to the lower limit set voltage all at once, but gradually rises from zero voltage according to the time constant by appropriately selecting the time constant determined by the first resistor _R48 and the capacitor _C11 . It seems to increase the pressure.

Further, a rotation abnormality detection circuit 30 of the fan 2
is a V connecting the fan 2 and the motor 1.
When the fan 2 stops due to a break in the belt 50, etc., the detected static pressure Pd decreases, for example, the minimum control static pressure P1 or _less . The detected static pressure Pd is compared with the set static pressure _P0 , which is set to a value around ₁ .
When the static pressure becomes lower than the set static pressure P ₀ , an abnormality in the fan 2 is notified. This detector 30 is a fourth detector for setting the set static pressure P ₀ .
The setting circuit 31 compares this set static pressure P ₀ and the detected static pressure Pd, and determines that the detected static pressure Pd is the set static pressure P ₀
A comparison circuit 32 outputs an H signal when and a relay R that operates a display circuit (not shown).

In the detector 30, _A11 is an operational amplifier,
R ₅₀ ~ _{R 54} are fixed resistors, R _v4 is variable resistors, T _r2 is
NPN type transistor, _D2 is a diode.

Next, the operation of the air conditioner configured as above will be explained.

First, the setting operation of the maximum control static pressure _P3 in the second setting circuit 15 will be explained by setting the initial condition of the control static pressure Ps of the setting device 12.

The variable resistor _Rv2 of the second setting circuit 15 is adjusted to set the maximum control static pressure _P3 to a large value, for example, to a settable maximum value.

The damper 9 of each terminal unit 8 of the air conditioner is fully opened, and then the operation of the device is started.

Then, at the start of operation, the detected static pressure Pd
is zero (atmospheric pressure is the standard), the controller 13 outputs a frequency setting signal V, which is an integral of the difference between the minimum control static pressure _P1 and the detected static pressure Pd, to the frequency converter 10. As a result, the motor 1 and therefore the fan 2 rotate, and the supplied air volume Q increases. Therefore, the detected static pressure Pd also gradually increases.

Since the maximum control static pressure _P3 is set large in the second setting circuit 15, the control static pressure Ps is always larger than the detected static pressure Pd, and as a result,
The rotation speed of the fan 2, in other words, the frequency setting signal V increases to the maximum value Vmax, and the supply air volume Q
is also the maximum air volume Qmax. Furthermore, this maximum air volume
At Qmax, the static pressure inside the ducts 6, 61 almost matches the required (minimum) static pressure set by design corresponding to this maximum air volume Qmax.

At this time, the initial value detection circuit 18 detects that the comparison circuit 24 outputs an H signal because the maximum control static pressure _P3 outputted from the second setting circuit 15 is larger than the detected static pressure Pd as described above. , the switch circuit 25 is turned on, the light emitting diode LED is energized, and the diode LED emits light.

Under this condition, the variable resistor _Rv2 of the second setting circuit 15 is adjusted to adjust the maximum control static pressure _P3.
The set value of is gradually decreased, and when the light emitting diode LED turns off, that is, when the set value of the maximum control static pressure _P3 and the detected static pressure Pd become equal, the set value is reduced. It holds. Note that the comparison circuit 24 has a slight hysteresis characteristic.

By doing so, the maximum air volume at the position Z where the static pressure detection section 11 of the main duct 6 is provided.
The maximum control static pressure P ₃ corresponding to Qmax can be easily set.

Note that the set pressure of the first setting circuit 14 is set by the variable resistor.
said minimum control static pressure by adjusting R _v1 to correspond to the minimum static pressure required at the terminal unit 8 as described above.
It is set to P ₁ .

After setting the initial conditions for the control standstill Ps in the setting device 12 in this way, the air conditioner is operated, and this operation will be explained below.

The damper 9 of each terminal unit 8 is adjusted, for example, so that the air volume Q becomes _Q2 , and an operation switch (not shown) is closed.

At this time as well, since the detected static pressure Pd is zero, the frequency setting signal V output from the controller 13 increases from zero in the same manner as described above. At this time, as shown in FIG. 7, the time constant of the lower limiter circuit 29 is small, and the boost rate of the signal voltage A of the circuit 29 is the same as the boost rate of the frequency setting signal V output from the controller 13 (FIG. 7 B). If it is faster than the
Until the frequency setting signal V output from the controller 13 reaches the minimum frequency setting signal Vlim,
The signal voltage input to the frequency converter 10 is regulated by the signal voltage A of the lower limiter circuit 29.

Conversely, as shown in FIG.
If the pressure increase rate is slower than the pressure increase rate in Figure B), contrary to the case in Figure 7, the frequency converter 1
The signal voltage input to 0 is regulated by the signal voltage (frequency setting signal V) output from the controller 13.

In this case as well, as described above, the signal voltage output from the controller 13 is gradually increased from zero voltage. In either case shown in FIGS. 7 and 8, the signal voltage (frequency setting signal V) input to the frequency converter 10 gradually increases from zero voltage, so the fan 2 The starting current for the motor 1 can be suppressed to a small value.

As the frequency setting signal V input to the frequency converter 10 increases, the output frequency increases, the rotational speeds of the motor 1 and the fan 2 increase, and the supplied air volume Q increases.

Further, as the frequency setting signal V increases, this signal V is fed back to the setting device 12, and the control static pressure Ps set by the setting device 12 also increases.

On the other hand, the static pressure detected by the rotation of the fan 2
Pd also increases.

Since the frequency setting signal V input to the frequency converter 10 is controlled by the controller 13 so that the detected static pressure Ps matches the control static pressure Ps, the detected static pressure Pd, that is, the static pressure inside the ducts 6, 61 is stabilized in the relationship between the frequency setting signal V ₂ and the control static pressure P _s2 corresponding to the supply air volume Q ₂ set by the damper.

Furthermore, from this state, the damper 9 of the terminal unit 8
A case will be explained in which the supply air volume Q is adjusted to decrease to _Q3 by operating it to the closed side.

In this case, first, the detected static pressure Pd is
The pressure is increased along the air blowing characteristic curve corresponding to the rotational speed.

Therefore, the detected static pressure Pd becomes larger than the control static pressure _Ps2 , and as a result, the frequency setting signal V output from the controller 13 decreases.

For this reason, the control static pressure set by the setting device 12
Ps also becomes smaller.

On the other hand, as the frequency setting signal V decreases, the rotation speed of the fan 2 also decreases, so the detected static pressure
Pd also becomes smaller.

In this way, similarly to the above, the detected static pressure Pd
is stabilized in the relationship between the frequency setting signal V ₃ and the control static pressure P _s3 corresponding to the air volume Q ₃ .

The same applies when the damper 9 is adjusted so that the supplied air volume Q increases from _Q2 .

Further, even if the damper 9 is adjusted so that the supplied air volume Q is close to zero, the lower limiter circuit 2
9 acts, the rotation speed of the fan 2 is the 6th
As shown in the figure, the rotational speed is maintained at a rotation speed corresponding to the minimum output frequency Vlim.

Therefore, it is possible to reliably prevent a situation in which the air volume is insufficient in the fan 2, resulting in liquid compression in the compressor during cooling operation, and damage to the compressor.

Further, during operation, if the V-belt 50 connecting the fan 2 and the motor 1 breaks and the fan 2 stops, the detected static pressure Pd becomes zero and the abnormality detector 30 of the fan 2 operates as described above. Then, the abnormality of fan 2 is displayed.

As described above, by providing the static pressure detection unit 11 at an arbitrary position Z in the main duct 6 before branching, and detecting and controlling the static pressure (Pd) at the position (Z), The static pressure inside the ducts 6 and 61 is determined by the supply air volume Q
The static pressure can always be controlled to the control static pressure Ps according to the
Therefore, in this embodiment, when a plurality of branch ducts 61 are provided from the main duct 6 to perform air conditioning in a plurality of rooms 7, the static pressure detection section 11 for controlling the rotation speed of the fan 2 is connected to the terminal unit 8. This is particularly effective when the main duct 6 cannot be provided at the entrance of the main duct 6 and must be provided midway before the main duct 6 branches. This is because the required static pressure on the inlet side of the terminal unit 8
While P ₁ is constant regardless of the supplied air volume Q,
Necessary static pressure in the middle of the main duct 6, that is, control static pressure
Ps changes in response to changes in the supplied air volume, and according to the above embodiment, the control static pressure
Even if Ps changes with the supply air volume Q, the control static pressure Ps corresponding to the supply air volume Q is automatically calculated,
This is because the rotation speed of the fan 2 can be controlled so that the detected static pressure Pd always matches the control static pressure Ps.

Note that in the above embodiment, the controller 13 controls the frequency converter 10 according to fluctuations in the supply air volume Q.
Although the output frequency of the frequency converter 10 is changed, the controller 13 may change the output frequency of the frequency converter 10 in accordance with a change in indoor temperature with respect to the set temperature of the plurality of rooms 7.

Further, a frequency converter is connected to a motor (not shown) that drives the compressor, and a parallel circuit of the controller and a lower limiter circuit is connected to the converter, and the minimum capacity is regulated while the frequency converter is connected to the frequency converter. The compressor may also have variable capacity depending on the load.

(Effect of the invention) As described above, the present invention connects the frequency converter 10 to the motor 1 of the fan 2 to control the rotational speed of the motor 1. A first setting circuit 14 sets a minimum control static pressure, and a first setting circuit 14 sets a maximum control static pressure corresponding to the maximum rotation of the motor 1. 2 setting circuit 15, and an arithmetic circuit 17 for calculating the necessary control static pressure in the ducts 6, 61 within the range of the minimum control static pressure and the maximum control static pressure and for the supply air volume. The control static pressure setting device 12
The static pressure detected by the static pressure detection unit 11 is compared with the control static pressure set by the setting device 12, and a frequency setting signal corresponding to the control static pressure that matches the detected static pressure is calculated. A series circuit is provided with a controller 13 that outputs a setting signal to the frequency converter 10, and a parallel circuit of a first resistor R ₄₈ , a second resistor R ₄₉ , and a capacitor C ₁₁ is connected in series to the power supply. furthermore, the first resistor R ₄₈ of the lower limiter circuit 29 is provided.
and the parallel circuit and the output side of the controller 13 are connected via a pair of diodes D ₄ and D ₅ with their cathodes facing each other, and these diodes
By connecting the connection point of D ₄ and D ₅ to the frequency converter 10, within the range of the minimum control static pressure and the maximum control static pressure, in the ducts 6 and 61,
A necessary control static pressure is set for the supply air volume, that is, a control static pressure is determined according to the supply air volume, and the motor 1 is controlled so that the static pressure detected by the static pressure detection unit 11 matches the control static pressure. By controlling the rotation speed of the motor 1, the static pressure in the ducts 6, 61 is controlled to a necessary control static pressure according to the supplied air volume.
By providing the lower limiter circuit 29, the minimum air volume of the fan 2 can be set appropriately, while reducing the required power for the heat exchanger 3 during cooling.
This makes it possible to reliably prevent liquid compression from occurring in the compressor. In addition, the signal voltage output from the lower limit limiter circuit 29, which outputs a signal voltage that gradually increases from zero voltage to the lower limit setting signal voltage (lower limit frequency setting signal Vlim) at the start of operation, or the signal voltage output from the controller 13. Since the motor 1 is started by the setting signal, the motor 1
The starting current can be reliably suppressed to a low level.
Damage to the motor 1 can be prevented.

[Brief explanation of the drawing]

Fig. 1 is a schematic sectional view of an embodiment of the present invention, Fig. 2 is a block diagram showing the control system, Fig. 3 is an electronic circuit diagram of the control system, and Fig. 4 is a diagram showing the supply air volume and static pressure. FIG. 5 is a relationship diagram showing the relationship between the frequency setting signal and control static pressure. FIG. 6 is a relationship diagram showing the relationship between the frequency setting signal and the output frequency. The figure is a diagram showing temporal changes in the frequency setting signal. DESCRIPTION OF SYMBOLS 1... Motor, 2... Fan, 3... Heat exchanger, 6... Duct, 7... Chamber, 10... Frequency converter, 11... Static pressure detection part duct, 12... Setting device, 13 ... Controller, 29 ... Lower limiter circuit, R ₄₈ ... First resistor, R ₄₉ ... Second resistor, D ₄ ,
_D5 ...Diode.

Claims (1)

[Scope of utility model registration request] Air conditioner 4 equipped with fan 2 and heat exchanger 3
Connect the ducts 6 and 61 to the ducts (6) and (6
1) In an air conditioner that supplies conditioned air to a plurality of rooms 7 via a
The rotational speed of the ducts 6 and 6 can be controlled.
A static pressure detection unit 11 for detecting the static pressure inside the ducts 6 and 61 is provided in the middle of the duct 61, and a first setting circuit 14 for setting the minimum control static pressure, and a maximum control circuit 14 for setting the minimum control static pressure, and a maximum control circuit corresponding to the maximum rotation of the motor 1. a second setting circuit 15 for setting static pressure; and a calculation for calculating the necessary control static pressure in the ducts 6, 61 within the range of the minimum control static pressure and maximum control static pressure and for the supply air volume. a control static pressure setter 12 comprising a circuit 17; a static pressure detected by the static pressure detection unit 11;
Compare the control static pressure set by the setting device 12,
a controller 13 that calculates a frequency setting signal corresponding to a control static pressure that matches the detected static pressure and outputs the setting signal to the frequency converter 10, and a first resistor R ₄₈ connected to the power source; A lower limiter circuit 29 consisting of a series circuit in which a second resistor R ₄₉ and a parallel circuit of a capacitor C ₁₁ are connected in series is provided;
Connection point between R ₄₈ and the parallel circuit and the controller 13
is connected to the output side of the frequency converter 10 via a pair of diodes D ₄ and D ₅ whose cathodes face each other, and the connection point of these diodes D ₄ and D ₅ is connected to the frequency converter 10. Air conditioner.