JPS6356195A - Refrigeration unit - Google Patents

Abstract

PURPOSE:To avoid the lowering of the torque of a compressor even if a refrigeration unit is operated at a frequency higher than the power-frequency, by driving a motor for compressor with an inverter power source which is matched with the voltage/frequency pattern to be the maximum voltage at the frequency higher than the power-frequency. CONSTITUTION:A power unit has an inverter 13 to supply a commercial power source 1 to a compressor 5 with voltage/frequency conversion and a voltage reduction device 14 to reduce the voltage of the commercial power source 1 to supply it directly to the compressor 5. These are selectively changed over by relay contacts 15, 16 and 17 and connected to the compressor 5. In operating the inverter power source, no torque will be so reduced even in the frequency range higher than the power-frequency that a superb output characteristic is obtained. In operating the commercial power source, the voltage is so reduced to that appropriate to the characterirstic of the motor of the compressor 5 by the voltage reduction device 14 thereby the proper operation of compressor 5 is performed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a refrigeration system equipped with a compressor that can be operated on both an inverter power source and a commercial power source.

(Prior art) Conventionally, as shown in Fig. 8, a commercial power source 1 and an inverter 2
Refrigeration with compressor 3 operated by both! A location is known. Commercial voltage VC is used for compression V13 electric fJ1 machine.
A type having a characteristic of 8 positive at commercial frequency fc is used, and in accordance with this characteristic, the voltage/frequency pattern of impark 2 is determined as shown by the chain line in FIG.

Note that 4 is a relay contact.

(Problem to be solved by the invention) However, in the above system, when the compressor 3 is driven by the inverter 2 at a frequency higher than the commercial frequency fc, the fifth
The torque decreases as shown by line 1'l C in the figure. Furthermore, the upper limit of the frequency of the inverter 2 cannot be increased much because the torque decreases and becomes insufficient.

The present invention was devised to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide an inverter that can increase the upper limit of the operating frequency of the inverter without causing a torque shortage due to compression. - To provide a commercial refrigeration system equipped with a compressor driven by two power sources.

[Structure of the Invention] (Means for Solving the Problems) The present invention sets the voltage/frequency pattern of the inverter power supply that drives the compressor so that the maximum voltage is at a frequency higher than the commercial frequency, and A voltage that adapts the compressor motor to the voltage/frequency pattern specifications and lowers the voltage supplied from the commercial power supply to the compressor motor during commercial power supply operation to the voltage value at the commercial frequency obtained from the voltage/frequency pattern. Descent! I connected the A station to commercial power.

(Function) Since the compressor motor is driven by an inverter power supply in accordance with the voltage/frequency pattern that causes the maximum voltage to rise at a frequency higher than the commercial frequency, compressor torque decreases even when operating at a frequency higher than the commercial frequency. There's nothing to do. Furthermore, during commercial power supply operation, the voltage is lowered by the voltage drop device to the voltage value at the commercial frequency in the voltage/frequency pattern and then supplied to the compressor, so the compressor can be operated efficiently.

(Example) Embodiments of the present invention will be described below based on the drawings.

As shown in FIG. 3, the refrigeration cycle of the refrigeration system includes a compressor 5, a compressor 6, a liquid receiver 7, an evaporator 8, an accumulator 9, a pressure cap 10, and the like. Compressor 5
The electric motor has a power supply device 11 for supplying power to it.
is connected.

The power supply device 11 also includes a control unit 12 for changing the frequency of the inverter based on the pressure detected by the pressure sensor 10.
are connected.

As shown in FIG. 1, the power supply device 11 includes an inverter device 13 that converts the voltage/frequency of the commercial power source 1 and supplies it to the compressor 5, and an inverter device 13 that lowers the voltage of the commercial power source 1 and supplies it directly to the compressor 5. The compressor 5 is connected to the compressor 5 by being selectively switched by relay contacts 15, 16, and 17.

As shown in FIG.
5 is closed by energization of the relay winding 15×, and the energization of these is controlled by a changeover switch 18.

For example, as shown in the figure, the relay winding 15
An auxiliary relay contact 17xb that enables energization of x is connected in series to relay winding 15x, so that inverter power and commercial power are not supplied to compressor 5 at the same time.

The voltage/frequency pattern of the inverter device 13 is set so that the maximum voltage is reached when the maximum frequency f exceeds the commercial frequency [C, as shown by the solid line B in FIG. 4.

The 'Ir1vJ machine used for the compressor 5 has specifications that efficiently match the voltage/frequency pattern B of the inverter device 13. The voltage drop device 14 is composed of, for example, a transformer, and is set to drop the commercial voltage VC to a voltage value V1 at the commercial frequency fc in the voltage/frequency pattern B. Further, on the input side of the inverter device 13, a primary current detection device 19 is provided as shown in FIG.

During inverter power operation, the inverter device 13 supplies power to the compressor 5! Power converted based on the voltage/frequency pattern B is supplied to the l1 machine. The electric motor of the compressor 5 is compatible with the voltage/frequency pattern B, and has good output characteristics without a decrease in torque as shown by the solid line in Fig. 5 even in a frequency range higher than the commercial frequency fc. 17.

On the other hand, during commercial power supply operation, power at the commercial frequency fc and commercial voltage VC is not directly supplied to the compressor 5 from the commercial power supply 1, but the voltage drop device 14 adjusts the voltage to match the characteristics of the motor of the compressor 5. V! compressor 5.
shall be operated properly.

Note that the inverter device 13 has a compression n5 storage: ljl.
As a function, when the load becomes large in the upper frequency range, that is, when the primary current value detected by one secondary current detection device becomes larger than a certain set value, the frequency is lowered by a predetermined value and the motor of the compressor 5 is This reduces the load on

However, if this protection function is activated in the low frequency Wl range immediately after the compressor 5 is started, the frequency will drop and the primary current will drop, but the secondary current will increase and the compressor 5 will stop. Sometimes. Therefore, as shown in the flowchart of Fig. 6, immediately after starting the compressor 5, the protection function is cut off until a certain period of time has elapsed by activating the timer, and the frequency is reduced even if the primary current value is greater than the set value of 1 fl. Control is performed to prevent the compressor 5 from stopping due to an increase in the secondary current without lowering the secondary current.

[Effects of the Invention] In summary, according to the present invention, the compressor can be operated with an inverter power supply without running out of torque in a frequency range higher than the commercial frequency, good output characteristics can be obtained even at high frequencies, and the operating frequency of the inverter can be reduced. It is possible to raise the upper limit of

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the driving power supply section of the compressor of the refrigeration system according to the present invention, FIG. A configuration diagram showing an example of a refrigeration cycle, FIG. 4 is a diagram showing a comparison between the voltage/frequency control of the present invention and a conventional inverter, and FIG. 5 is a diagram showing frequency characteristics of compressor torque of the present invention and the conventional inverter. Figure, 6th
The figure is a flowchart showing frequency control for compressor protection during inverter operation, Figure 7 is a circuit diagram showing an inverter equipped with a primary current detection device, and Figure 8 is a flowchart showing frequency control for compressor protection in a conventional refrigeration system. 'Ii source section circuit diagram. In the figure, 1 is a commercial power supply, 5 is a compressor, 6 is a condenser, 7 is a liquid receiver, 8 is an evaporator, 9 is an accumulator, 10 is a pressure sensor, 11 is a power supply device, 12 is a control unit, and 13 is a Inverter device, 14 voltage drop device, 15.16.17 relay contact, 15×. 16x and 17x are relay windings, 17xb is an auxiliary relay contact, 18 is a changeover switch, and 19 is a primary current detection device. Figure 4 Figure 5 Figure 7

Claims (1)

[Claims] In a refrigeration system that has a compressor that is driven by an inverter power source or a commercial power source by switching, the voltage/frequency pattern of the inverter power source is set so that the maximum voltage is at a frequency higher than the commercial frequency, and the compressor motor is /A voltage drop device is connected to the commercial power supply to conform to the frequency pattern specifications and to drop the voltage supplied from the commercial power supply to the compressor motor during commercial power supply operation to the voltage value at the commercial frequency obtained from the voltage/frequency pattern. A refrigeration device characterized by: