JPH0549903B2 - - Google Patents

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to an air conditioning control system for railway vehicles that prevents accidents such as refrigerant liquid compression, has a wide continuous control range of cooling capacity, and is highly efficient. be.

[Prior Art] FIG. 5 is a block diagram showing a conventional air conditioning control device for a railway vehicle.

In the figure, 1 is a DC main line, one terminal 1a is applied with a reduced DC voltage received from a DC high-voltage overhead line (not shown), and the other terminal 1b is applied.
is grounded.

2 is a power supply capacitor connected between both ends of the DC main line 1, 3 is an inverter that converts the voltage supplied from the power supply capacitor 2 into variable voltage variable frequency (VVVF) three-phase AC, and 4 is a power supply capacitor connected to the output frequency of the inverter 3. This is a control circuit that controls the

5 is a compressor for compressing refrigerant, 6 is an outdoor fan for condensing the refrigerant compressed by the compressor 5, and 7 is a refrigerant that is condensed by the outdoor fan 6 and further expanded by a capillary tube (not shown). This is an indoor fan for a cooler that evaporates water, and both of these are driven by the three-phase AC output of the inverter 3.

Next, the operation of the conventional device shown in FIG. 5 will be explained.

As is well known, air conditioners for railway vehicles are supplied with low-voltage power through a lead-in busbar, and this low-voltage power is originally 600V or 300V DC. Therefore, the electric train overhead line power supply (DC1500V) is converted to DC600V by a DC/DC converter power supply (not shown).
After being converted to ±10% (when the inverter output side is three-phase AC440V) or DC300V±10% (when the inverter output side is three-phase AC200V), power is supplied to the inverter 3.

In addition, since maintenance and inspection of air conditioners for railway vehicles is difficult, for example, the refrigerant cycle including the compressor 5 and welded piping has a completely sealed structure to prevent refrigerant from leaking, improving reliability and making maintenance easier. The unnecessary conditions are met. Therefore, a three-phase induction motor (not shown) that drives the compressor 5 is also included in the enclosed structure, and the inverter 3 drives the hermetically sealed compressor 5 via the three-phase induction motor to provide cooling. Performs a variable function of ability.

In such a sealed structure, if the inverter 3 is operated at an output frequency of 30 Hz or less, it becomes impossible to supply oil to the bearings of the compressor 5 (that is, oil supply by rotation of the shaft pump), resulting in seizure of the shaft. . Therefore, the lower limit of the control range of the compressor 5 by the inverter 3 is 30 Hz, which corresponds to the rotation speed of the bipolar motor of 1800 rpm (corresponding to the lower limit of the cooling capacity).

The compressor 5 turns the low-pressure refrigerant into high-temperature, high-pressure vapor and sends it to the condenser. The condenser having the outdoor fan 6 cools and condenses the refrigerant while keeping it at a high pressure, and turns it into a liquid. A capillary tube then expands the high-pressure liquid refrigerant into cool, wet vapor that is delivered to the cooler. The cooler having the indoor fan 7 applies heat from the air inside the vehicle to the refrigerant, converts it into low-pressure superheated steam, and sends it to the compressor 5 again. By repeating the above cycle, the indoor fan 7 sends cold air into the vehicle.

Normally, the cooling capacity is controlled by changing the driving frequency (rotation speed) of the compressor 5, but the compressor 5 has lubricating oil built-in, and in order to circulate this lubricating oil, the lower limit of the driving frequency is set. is set to 30Hz. Further, since the refrigeration cycle was set with the rated drive frequency of the compressor 5 as 60Hz, the upper limit of the drive frequency is 60Hz. Therefore, in the maximum cooling capacity state, the output frequency of the inverter 3 is 60Hz, and the output frequency of the compressor 5, outdoor fan 6, and indoor fan 7 is 60Hz.
is driven with a frequency of 60Hz and a voltage proportional to that frequency.

When the temperature inside the vehicle decreases and cooling capacity is no longer required, the output frequency of the inverter 3 changes to the lower limit value in response to a signal from a temperature sensor (not shown).
Reaching 30Hz. The lowest driving frequency at this time is
The cooling capacity at 30Hz is approximately 50% of the maximum cooling capacity when operating at 60Hz.

Furthermore, when reducing the cooling capacity, since the inverter 3 cannot output a frequency lower than 30 Hz, the output of the inverter 3 is stopped and the drive of the compressor 5 is stopped. In other words, the maximum cooling capacity
Since cooling drive control is impossible when the temperature is below 50%, the drive of the compressor 5 is stopped to adjust the temperature inside the vehicle. At this time, the outdoor fan 6 and the indoor fan 7
It also stopped driving. To enter the air blowing state, a mode changeover switch (not shown) must be operated.

Furthermore, it is generally not desirable to repeatedly start and stop the compressor 5, and it is well known that lowering or stopping the driving frequency of the indoor fan 7 together with the compressor 5 reduces cooling efficiency. .

FIG. 6 is a block diagram illustrating another conventional example devised in consideration of the latter point mentioned above. 8 is a fixed voltage fixed frequency (CVCF) inverter;
An outdoor fan 6 and an indoor fan 7 are connected to the output terminal. On the other hand, only the compressor 5 is connected to the inverter 3 of the VVVF.

According to the configuration shown in FIG. 6, since the indoor fan 7 is always driven at the highest frequency of 60 Hz, the cooling efficiency increases when the driving frequency of the compressor 5 reaches the lower limit value.
However, since the lower limit of the driving frequency of the compressor 5 is 30 Hz and the driving frequency of the indoor fan 7 remains at 60 Hz, the cooling capacity is only reduced to 70% of the maximum. Therefore, below that temperature, the compressor 5 is stopped to control the temperature inside the vehicle.

[Problems to be Solved by the Invention] As described above, in the conventional air conditioning control device for a railway vehicle, if all the motors are driven and controlled by only one inverter 3, the cooling efficiency decreases, and the compressor 5
Since the drive frequency is limited to the lower limit of 30Hz,
The cooling capacity can only be reduced to 50%.
Therefore, there is a restriction on the lower limit of the cooling capacity, and even when the inside of the train is quiet, such as on a commuter train, weak cooling cannot be achieved, resulting in excessive cooling, making it difficult to control the air conditioning comfortably.

In addition, indoor fan 7 is installed to increase cooling efficiency.
If the CVCF was always driven at 60 Hz by the inverter 8, the cooling capacity could only be reduced to 70%, resulting in a problem that the compressor 5 would have to be stopped and started more frequently.

This invention was made to solve the above-mentioned problems, and it prevents accidents such as refrigerant liquid compression, and also allows the evaporator blower (i.e., By controlling the rotation speed of the indoor fan (indoor fan) to a lower limit value that is smaller than the lower limit value of the compressor, the continuous control range of cooling capacity is expanded while maintaining cooling efficiency to the maximum, and the frequency of stopping and starting the compressor is reduced. The purpose is to obtain an air conditioning control device for railway vehicles that can be used in a railway vehicle.

[Means for Solving the Problems] The air conditioning control device for a railway vehicle according to the present invention includes a first inverter that drives a refrigerant compressor with a three-phase VVVF, a second inverter that drives an indoor fan, and a first inverter that drives an indoor fan. The first to control the output frequency of the inverter
A control circuit, a second control circuit that controls the output frequency of the second inverter, and an outdoor fan for a condenser that condenses refrigerant compressed by the compressor, and the outdoor fan is connected to the output terminal of the second inverter. At the same time, the second inverter acts as a CVCF inverter with a constant output at the frequency upper limit until the output frequency of the first inverter reaches a predetermined lower limit within the control range, and when the output frequency of the first inverter reaches the lower limit. From this point on, it acts as a VVVF inverter, and when the output frequency of the first inverter reaches the lower limit, the second control circuit sets the output frequency of the second inverter to be smaller than the lower limit for the first inverter. The output frequency of the second inverter is decreased within a control range having a lower limit value, and the output frequency of the second inverter is lowered to a lower limit value that is not subject to frequency limitations by the compressor.

[Function] In this invention, the indoor fan and the outdoor fan are driven and controlled by the second inverter to prevent accidents such as refrigerant liquid compression, and the output frequency of the first inverter is set to a lower limit value (for example, 30 Hz). Until then, the second inverter acted as a CVCF inverter with a constant output at the upper limit (for example, 60Hz), and from the moment the output frequency of the first inverter reached the lower limit, the second inverter acted as a VVVF inverter. , lower the output frequency to a lower limit value (for example, 10Hz) that is not subject to frequency limitations by the compressor.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing a partial circuit diagram of an embodiment of the present invention.
7 to 7 are similar to the conventional device described above.

3A is the first inverter of the VVVF which is composed of three pairs of transistors and drives the compressor 5;
The range of its output frequency (voltage) is 60Hz to 30Hz (440V to 220V) as shown in FIG.

3B is a second inverter that is composed of three pairs of transistors like the first inverter 3A and drives the outdoor fan 6 and indoor fan 7, and as shown in FIG. It has a range of output frequency (voltage), and when the output frequency of the first inverter 3A reaches the lower limit, that is, 30Hz.
It is now possible to switch from CVCF to VVVF.

4A applies a modulation pulse to the transistor base in the first inverter 3A, and
4B is a second control circuit that applies a modulation pulse to the transistor base of the second inverter 3B to control the output frequency of the second inverter 3B; 4C is a temperature sensor 11 to be described later; A third control circuit for controlling the first control circuit 4A and the second control circuit 4B according to the temperature signal from the
It is a control circuit.

10 is a switch that turns on and off the DC voltage applied to the DC main line 1; 11 is a thermistor or temperature sensor that detects the temperature inside the vehicle and outputs a temperature signal to the third control circuit 4C; and 12 is a switch to the third control circuit 4C. It is a connected on/off switch.

Next, each inverter 3A, 3B shown in FIG.
The operation of the embodiment of the present invention will be described with reference to a characteristic diagram of the cooling capacity for the air conditioner.

When the switch 10 and switch 12 are closed to start cooling the vehicle, the first control circuit 4A controls the output frequency of the first inverter 3A to 60Hz. Therefore, the compressor 5 is driven at its maximum cooling capacity.

Further, the second control circuit 4B controls the output frequency of the second inverter 3B to a CVCF state of 60Hz, and the cooling capacity at this time is 100Hz as shown at point P in FIG.
%.

When the temperature sensor 11 detects that the temperature inside the vehicle has decreased, the output frequency of the first inverter 3A is gradually decreased by the first control circuit 4A, and the driving frequency of the compressor 5 is lowered to the lower limit of 30 Hz. At this time, since the output frequency of the second inverter 3B remains at 60 Hz, the cooling capacity becomes 70% as shown by point Q in FIG. On the other hand, refrigerant efficiency is improved for the reasons mentioned above.

If it is necessary to further reduce the cooling capacity, the output frequency of the first inverter 3A remains at 30 Hz, and the second inverter 3B is switched from CVCF to VVVF to reduce its output frequency. Second
When the output frequency of inverter 3B drops to 30Hz, the cooling capacity is 50% as shown by point R in Figure 4.
becomes.

At this time, during the period from point Q to point R, the output frequency of the second inverter 3B, that is, the rotation speed of the indoor fan 7, is always higher than the output frequency of the first inverter 3A, that is, the rotation speed of the compressor 5.
Cooling efficiency has improved compared to conventional systems.

The lower limit of the output frequency of the second inverter 3B is
Since it is not limited by the compressor 5 like the first inverter 3A, for example, as shown in FIG.
Can be set to 10Hz.

Therefore, the cooling capacity can be further reduced to about 30 to 40% as shown by point S. At this time, it is not preferable to set the output frequency of the second inverter 3B to 0 because the compressor 5 is driven at 30 Hz, but there is no problem in reducing the output frequency to about 10 Hz.

If the cooling capacity is to be attenuated below point S in FIG. 4, the output of the first inverter 3A may be stopped to stop the drive of the compressor 5, as in the conventional case.

In this way, the rotation speed of the compressor 5 and the indoor fan 7 can be controlled continuously using each of the inverters 3A and 3B. At this time, the rotation speed of the compressor 5 is maintained above the lower limit value (30 Hz), and the rotation speed of the indoor fan 7 is lowered to the lower limit value (10 Hz) lower than 30 Hz, thereby further reducing the cooling capacity.

Also, the outdoor fan 6 is connected to the second indoor fan 7.
Since it is connected to the output terminal of the inverter 3B and both are controlled simultaneously, the evaporation capacity and condensation capacity of the refrigerant are reduced, and accidents such as liquid compression of the refrigerant can be prevented.

That is, if the rotation speed of the indoor fan 7 decreases, the amount of heat exchanged indoors decreases, but at the same time, the amount of heat exchanged indoors decreases.
Since the number of revolutions of the compressor decreases and the amount of heat exchanged outdoors also decreases, an equilibrium state of the refrigerant temperature is maintained and the refrigerant is prevented from being returned to the compressor 5 in a liquid state. Conversely, if the rotational speed of the indoor fan 7 increases and the amount of heat exchange increases, the rotational speed of the outdoor fan 6 simultaneously increases and the amount of heat exchanged outdoors also increases, and the equilibrium state of the refrigerant temperature similarly changes. This prevents the refrigerant from being returned to the compressor 5 in a liquid state.

In addition, liquid compression of refrigerant on a ship occurs when heat exchange in the indoor fan 7 is insufficient and the refrigerant cannot be sufficiently vaporized and is sucked into the compressor 5 in a liquid state. If this continues, it will lead to damage to the compressor 5.

The liquid compression phenomenon of the refrigerant is likely to occur when the temperature is relatively low and cooling operation is performed under low load conditions, especially when the heat load is relatively small such as during the intermediate period or early in the transition period. It is also likely to occur when the air filter of the indoor fan 7 becomes clogged and the heat exchange effect becomes insufficient, or when frost buildup occurs on the heat exchanger.

Normally, in order to prevent the liquid compression phenomenon of refrigerant, the indoor temperature, refrigerant pipe pressure (low pressure side), and suction side pipe temperature are detected, and the second inverter 3B turns on the indoor fan 7 within a range that does not cause the liquid to be compressed. All you have to do is control the rotation speed. However, in the air conditioner for a railway vehicle, it is necessary to realize simplification from the viewpoints of durability, reliability, long life, and economy.

In the embodiment of the present invention, in order to reduce the cooling capacity as described above, the second inverter 3B whose loads are the outdoor fan 6 and the indoor fan 7 is controlled, but at this time, the liquid compression state of the refrigerant is prevented. Therefore, it is necessary to control the operation duration, etc. according to the indoor temperature. In this case, the second inverter 3
Since the frequency of B can be arbitrarily lowered or increased to the operating range of weak cooling capacity of 30Hz or less, frequency control according to the indoor temperature prevents liquid compression of the refrigerant while expanding the operating range of weak cooling capacity. Needless to say, it is possible to do so.
Moreover, the structure does not become particularly complicated, and the requirements for the air conditioner for railway vehicles can be met.

In addition, as a special feature of the air conditioner installed in a railway vehicle, when the rotation speed of the compressor 5 and the blower, that is, the indoor fan 7 is changed, the interior lights and cold air duct members installed on the ceiling and surrounding area of the vehicle are affected. etc,
Resonance phenomena occur due to changes in vibration frequency due to changes in the rotation of the electric motor, changes in air volume and speed due to changes in the rotation speed of the blower blades, and changes in the noise generated when the wind collides with duct members.

This resonance phenomenon tends to be particularly noticeable in the low frequency range, and is a cause of in-vehicle noise. However, by using inverters 3A and 3B that can change the frequency continuously, the noise inside the car can be prevented by artificially quickly passing through the resonant frequency region (jumping) and selecting a frequency other than the resonant frequency. can.

[Effects of the Invention] As described above, according to the present invention, the first inverter drives the compressor for refrigerant compression at three-phase variable voltage and variable frequency, the second inverter drives the indoor fan for the cooler, A first control circuit that controls the output frequency of the first inverter, a second control circuit that controls the output frequency of the second inverter, and an outdoor fan for a condenser that condenses refrigerant compressed by the compressor. An outdoor fan is connected to the output terminal of the second inverter, and the second inverter operates as a CVCF with a constant output at the upper frequency limit until the output frequency of the first inverter reaches a predetermined lower limit within the control range.
The second control circuit acts as a VVVF inverter from the point when the output frequency of the first inverter reaches the lower limit value.
When the output frequency of the inverter reaches the lower limit value, the output frequency of the second inverter is reduced in a control range having a lower limit value smaller than the lower limit value for the first inverter, and the lower limit value is not subject to frequency limitation by the compressor. In addition to lowering the output frequency of the second inverter to a maximum of 100%, the indoor fan and outdoor fan are driven by the same second inverter to prevent accidents such as liquid compression of the refrigerant, and to maintain continuous cooling capacity without sacrificing cooling efficiency. This has the effect of providing an air conditioning control device for railway vehicles that can expand the control range.

[Brief explanation of the drawing]

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 output of the first inverter shown in FIG. 1, and FIG. 3 is a diagram showing the output of the first inverter shown in FIG. FIG. 4 is a characteristic diagram showing the cooling capacity of the embodiment device shown in FIG. 1, FIG. 5 is a block diagram showing a conventional air conditioning control device for railway vehicles, and FIG. 6 is another conventional example. FIG. 3A...first inverter, 3B...second inverter, 4A...first control circuit, 4B...second control circuit, 5...compressor, 6...outdoor fan, 7...
Indoor fan. In the drawings, the same reference numerals indicate the same or corresponding parts.

Claims (1)

[Claims] 1. A first inverter that drives a refrigerant compressor at a three-phase variable voltage variable frequency, a second inverter that drives an indoor fan for a cooler, and an output frequency of the first inverter. a first control circuit that controls the output frequency of the second inverter; a second control circuit that controls the output frequency of the second inverter; and an outdoor fan for a condenser that condenses the refrigerant compressed by the compressor; The outdoor fan is connected to the terminal, and the second inverter operates as a fixed voltage, fixed frequency inverter with a constant output at the upper frequency limit until the output frequency of the first inverter reaches a predetermined lower limit within the control range. The first inverter operates as a variable voltage variable frequency inverter from the time when the output frequency of the first inverter reaches the lower limit value, and the second control circuit controls the output frequency of the first inverter to reach the lower limit value. When the second
An air conditioner for a railway vehicle, characterized in that the output frequency of the inverter is reduced in a control range having a lower limit value smaller than the lower limit value, and the output frequency of the second inverter is lowered to a lower limit value that is not subject to frequency restrictions by the compressor. Control device.