JPS60111842A - Refrigerator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a refrigeration system, and more particularly to an improvement in a refrigeration system that uses a frequency converter to control the rotational speed of a compressor.

[Prior art]

Refrigeration systems that use a frequency converter to control the rotation speed of a compressor are rapidly attracting attention in recent years from the standpoint of variable refrigerating capacity because the rotation speed of the compressor can be varied continuously.

FIG. 1 is a block diagram showing an example of a refrigeration system driven by a variable frequency system, where l is a compressor that compresses and outputs refrigerant, 2 is a condenser, 3 is an expansion valve, and 4 is an evaporator. ℃, these constitute a refrigeration cycle by being connected in a closed loop.

5 is a frequency converter that varies the frequency of the AC power supply supplied to the electric motor provided in the pressure generator 1; 6 is a frequency converter that changes the frequency of the AC power supply to detect the low pressure in the refrigeration cycle according to the output of the pressure detector 7; This is a controller that controls 5.

In a refrigeration system configured in this way, when the load is large, the pressure on the low pressure side of the refrigeration cycle increases,
Along with this, the output of the pressure detector 7 also increases. The controller 6 compares the set pressure and the output of the pressure detector 7 at fixed intervals, for example, every 20 seconds, and controls the frequency converter 5 to compress when the output of the pressure detector 7 is higher than the set pressure. Increase the power frequency supplied to the machine's motor. In this way, when the power frequency is increased, the rotational speed of the compressor 1 is increased and the cooling capacity is improved. Here, when the pressure on the low pressure side in the refrigeration cycle becomes less than the set value IN shown in the second section, the controller 6 fixes the output frequency of the frequency converter 5 as shown in FIG. Furthermore, when the pressure on the low pressure side becomes less than the set value OUT shown in FIG. The compressor 10 rotation speed is lowered as shown in FIG. When the output frequency of the frequency converter 5 reaches the practical lower limit frequency, the frequency rapidly decreases to zero, and the compressor 10 rotations are stopped.

Next, the pressure on the low pressure side of the refrigeration cycle reaches the set value IN.
When the frequency exceeds the practical lower limit frequency, the controller 6 controls the frequency converter 5 to generate an output whose frequency gradually increases from the practical lower limit frequency, and starts operating the compressor 1.

However, in the refrigeration system with the above configuration, when the frequency drops to the practical lower limit and the pressure on the output side becomes less than the set value OUT, the compressor l will stop.
At 0KHz, the overall capacity is 50-50%, which may cause the cooling to stop even though the object to be cooled has not cooled down yet, resulting in slow cooling, or conversely, restarting after stopping at 30Hz.
1 during high loads such as after defrosting.
There is a problem that it takes a long time to reach the 00 frequency, and the pulldown becomes long, so it takes a long time to cool down.

[Summary of the invention] Therefore, the object of this invention was to solve the above problem, and when one frequency drops to the lower limit, it is fixed at that frequency, and when restarting, operation starts from 100% frequency. This provides a refrigeration system with improved cooling characteristics.

[Embodiments of the invention]

FIG. 4 is a block diagram showing an embodiment of the refrigeration system according to the present invention, and the same parts as in FIG. 1 are designated by the same reference numerals. In the same figure, 8 is a controller that controls the frequency converter 5 in response to the output of the pressure detector 7, and is used when the output signal of the pressure detector 7 decreases beyond the lower limit set value. The frequency converter 5 is controlled so as to generate an output at the lower limit frequency, and the frequency converter 5 is controlled so as to generate an output at 100% frequency to drive the compressor 1 at the start of startup. , otherwise the configuration is the same as in the case of FIG.

In a refrigeration system configured in this manner, when the load is large, the pressure on the low pressure side of the refrigeration cycle increases.

After the refrigerant pressure on the low pressure side is detected by the pressure detector 7, its output signal is supplied to the controller 8. The controller 8 outputs the output signal of the pressure detector 7 at regular intervals (
For example, every 20 seconds), the refrigerant pressure on the low pressure side shown in FIG. 5 is determined to be higher than the set value IN.

This controller 8 controls the frequency converter 5 to increase the output frequency, thereby increasing the rotational speed of the compressor 1 and increasing the cooling capacity. Next, when the refrigerant pressure on the low pressure side becomes equal to or less than the set value IN as shown in FIG. 5, the controller 8 controls the output frequency of the frequency converter 5 to remain unchanged as shown in FIG. Next, when the controller 8 detects that the refrigerant pressure on the low pressure side has decreased to the east and has become below the set value OUT, the frequency converter 5
The rotation speed of the compressor 10 is lowered by executing control to lower the output frequency of the compressor as shown in FIG. 6 in accordance with the pressure. Here, when the output frequency of the frequency converter 5 reaches the practical lower limit frequency, the controller 8 and the frequency converter 5 continue to operate with the output frequency fixed at the lower limit value as shown in FIG.

If the refrigerant pressure on the low pressure side does not exceed the set value IN even if the operation at this practical lower limit frequency continues for more than a predetermined set time, the output frequency of the frequency converter 5 will change as shown in FIG. is set to zero and the compressor is stopped.

Next, as the compressor stops, the refrigerant pressure on the low pressure side decreases to the fifth level.
As shown in the figure, when the value rapidly increases and exceeds the set value IN, the controller 6 generates an output of 100% frequency from the frequency converter 5 as shown in FIG. drive. Then, when the refrigerant pressure of the low pressure 1i111 decreases beyond the set value IN, the same control as in the above case is repeated.

〔Effect of the invention〕

As explained above in 4*, in the refrigeration system according to the present invention, in order to continue operating the compressor by fixing it at the practical limit frequency when the load is low, the operation continues until all the objects to be cooled are cooled. I can do it. In addition, since it is driven at 100% frequency when restarting after a stop, it can be pulled down quickly even under high loads after defrosting, which helps keep products fresher. I can do it

[Brief explanation of drawings]

Figure 1 is a schematic diagram of the configuration of a conventional refrigeration system and its control system, Figures 2 and 3 are characteristic diagrams showing the relationship between refrigerant pressure and frequency on the low pressure side, and Figure 4 is a diagram of this control system. 5 and 6 are characteristic diagrams showing the relationship between refrigerant pressure on the low pressure side and frequency. FIG. l... Compressor, 2... Condenser, 3... Expansion valve, 4
... Evaporator, 5... Frequency converter, 7... Pressure detector, 8... Controller. Note that the same or equivalent parts in the figures are indicated using the same reference numerals. Agent Masuo Oiwa (2 others) Figure 1 Figure 2 Figure 4

Claims (1)

[Claims] (1) A refrigeration cycle in which a compressor, a condenser, an expansion valve, and an evaporator are connected in a closed loop, a frequency converter that varies the power frequency supplied to the electric motor that drives the compressor, and a low-pressure side of the refrigeration cycle. It has a pressure detector that detects the refrigerant pressure at the refrigerant, and a controller that controls the frequency converter using the output of the pressure detector as input, and the controller controls the frequency converter when the refrigerant pressure becomes below a set value. Deceleration control corresponding to the pressure is executed, and when the output frequency of the frequency converter drops to a predetermined wave number during deceleration, operation control is executed with the frequency fixed at the practical lower limit frequency, and when restarting, the frequency converter outputs 100% % of frequency! A refrigeration system that performs control to generate output and supply it to an electric motor of a compressor.