JPS6294764A - Drive circuit for motor of 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] [Industrial Application Field] The present invention relates to a motor drive circuit for a refrigeration system, and in particular, to a motor drive circuit for a refrigeration system, in particular, when the power source for driving the motor switches between a commercial power source and an inverter circuit to drive the motor. The present invention relates to a motor drive circuit for a suitable refrigeration system.

[Conventional technology]

One conventional motor drive circuit is disclosed in Japanese Patent Application Laid-Open No. 59-221579.
The motor is operated continuously (
However, when cooling is not required, when the motor overload protection is activated, or when the motor is defrosted, the motor stops and restarts using the inverter circuit.

[Problem that the invention seeks to solve]

In the above conventional technology, when starting a motor using an inverter circuit, a large starting torque is required, so a large starting current flows, but consideration is given to preventing this large starting current from flowing into the inverter circuit. This results in an increase in the power supply capacity of the inverter circuit, an increase in the capacity of the power element, and problems such as heat dissipation. Moreover, most of the troubles with the motor occur during startup, which has a negative effect on the reliability of the inverter circuit.

An object of the present invention is to prevent a large starting current from flowing through an inverter circuit of a motor drive circuit of a refrigeration system.

Means for Solving Problems] The above object is to provide a switching means for switching between a compressor motor driven by a commercial power supply or an inverter circuit, a commercial power supply or an inverter circuit, and a control for controlling switching of the switching means. In a motor drive circuit for a refrigeration system comprising a
This is achieved by the control unit controlling the switching means so that, when switching the switching means from the commercial power supply to the inverter circuit, the motor is driven by the commercial power supply for a predetermined period of time or more before the switching. .

[Effect]

When the motor is driven by the inverter circuit, the control section switches the switching means to switch from the commercial power source to the inverter circuit after the predetermined period of time in order to drive the motor with the commercial power source for a predetermined period of time. This prevents a large current from flowing into the inverter circuit for a certain period of time during startup.

〔Example〕

The present invention will be explained in detail below based on the embodiment shown in FIG.

1 is a commercial power source, 2 is a switching relay for switching between the commercial power source and the inverter circuit, 3 is a compressor motor, 4 is an AC control element when the motor is driven by the commercial power source, and 5 is an inverter circuit. Reference numeral 6 denotes a control circuit, which will be explained in detail in FIG. One end of the commercial power source 1 is connected to a contact B of a switching relay 2' via an AC control element 4, and a contact A is connected to a contact A of the switching relay 2 via a motor 3. Further, a contact B of the switching relay 2 is connected to the other end of the commercial power supply l. The output of the inverter circuit 5 is connected to contacts C of the switching relays 2 and 2'. The control circuit 6 is connected to the AC control element 4 and the inverter circuit 5 by human output lines.

When the motor 3 is driven by the commercial power supply 1, the switching relays 2 and 2' have contacts connected between A and B by the control circuit 6, and are turned on and off by the AC control element 4. When the motor 3 is driven by the inverter circuit 5, the contacts of the switching relays 2 and 2' are brought into continuity between A and C by the control circuit 6.
Further, the inverter circuit 5 is operated by a signal from the control circuit 6 to perform inverter driving.

FIG. 2 is a block diagram of a control circuit that controls the refrigerator. 7 is each temperature sensor, 8 is an amplifier for amplifying the signal from the temperature sensor, and 9 is a control microcomputer. IO is a switch (for example, a rapid cooling start button) for switching from commercial power supply driving to driving using an inverter circuit. A driver circuit 11 drives the AC control element 4, the switching relays 2 and 2', and the like. 12 is a circuit (consisting of a photocoupler or the like) that electrically insulates the control circuit 6 and the inverter circuit 5 and transmits the drive output signal of the inverter circuit 5 and the protection signal of the motor 3 when the inverter is driven. . 3 to 5 are time charts showing the timing of switching from driving the motor 3 by the commercial power source 1 to driving the motor 3 by the inverter circuit 5. FIG. TY indicates a starting point at which the motor is started to be driven by the commercial power source, immediately before the motor is driven by the inverter circuit. T indicates a stable point where the motor drive load becomes smaller from the starting point T7 and the motor drive becomes stable. 1. is the stable point T from the starting point T7.

It is a certain amount of time until E is an operation signal for the switch 10. The motor 3 is driven by the commercial power source 1, as shown in FIGS.
' contacts are A-B open ring connections. Therefore, the motor 3 is controlled by the AC control element 4. In this case, the signals from each temperature sensor 7 are sent to the amplifier 8 and the microcomputer 9 to repeat the intermittent operation so that the temperature of the object to be cooled remains constant. In this state, when the switch IO installed outside the refrigerator is pressed (to further cool the interior of the refrigerator, shorten the freezing time, etc. to quickly return to an appropriate cooling state when the temperature inside the refrigerator is high), the switching relay 2 and 2' contact is A-
8 is open and A-C is conductive. This timing is as shown in the time chart of Fig. 3. When the motor 3 is driven by the commercial power source I for a certain period of time or more, if the signal E of the switch 10 is manually applied, the switching relays 2 and 2' are switched to the commercial power source I. The power source 1 is immediately switched to the inverter circuit 5. Next, as shown in FIG. 4, when the switch fIO signal E is input manually at a point in time within a certain period of time when the motor 3 is powered by the commercial power source 1, the motor 3 is further driven by the commercial power source 1 for the remaining time t2. When this point is reached, switch to the inverter circuit.

Further, FIG. 5 shows that when the motor 3 is being driven by the commercial power source 1 and is intermittently stopped due to the output signal of the temperature sensor 7 in FIG. 2, when the signal E of the switch 10 is input manually, the motor 3 is turned on After time t3 (the time during which the refrigerant pressure in the refrigeration system is balanced) has elapsed and the motor t1 is driven by the commercial power source for a certain period of time, it is switched to the inverter circuit.

The above switching is performed by detecting the phase of the commercial power supply 1 and switching the relay 2 at the zero cross point to prevent the motor 3 from stopping or locking.

The above explanation has been given using examples of motor intermittent drive with commercial power supply and drive with an inverter circuit, but when driving the motor with only the impark circuit 5, there are also operations after power is turned on, after defrosting, and overload protection operation is resumed. Regarding time, be sure to use commercial basket #
(It goes without saying that the present invention also includes driving the motor in the inverter circuit 5 after the motor has been operated for a certain period of time.

〔Effect of the invention〕

As described above, in the present invention, since the motor 3 is not started in the inverter circuit 5, the power supply capacity of the inverter circuit 5 is sufficient to maintain the operation below the motor 3 starting torque (load torque matched to the rotation speed). This is advantageous because the power element capacitance can be set small and heat can be easily dissipated. Furthermore, since commercial operation is performed for a certain period of time, the inverter circuit 5 is driven when the pressure balance within the refrigeration cycle is stable, so that the power burden on the inverter circuit 5 is further reduced.

[Brief explanation of drawings]

FIG. 1 shows the motor drive circuit of the present invention, FIG. 2 is a block diagram of the control circuit, and FIG. 3 shows a signal E that switches the motor 3 to the inverter circuit 5 after a certain period of time when the motor 3 is driven by a commercial power supply l. Figure 4 is a time chart of the pattern in which switching signal E is input when the motor 3 is driven for a certain time within a certain period of time when driven with commercial power supply l, Figure 5 is a time chart of the pattern in which switching signal E is input when motor 3 is driven with commercial power supply 1. FIG. 6 is a time chart of pattern 4 in which the switching signal E is input when the motor 3 is stopped. FIG. 6 is a flowchart explaining the control operation of the microcomputer. DESCRIPTION OF SYMBOLS 1...Commercial power supply, 2...Switching relay, 3...Motor, 4...AC control element, 5...Inverter circuit,
6... Control circuit, 7... Temperature sensor, 8... Amplifier, 9... Refrigerator control microcomputer, 1
o... Switch for switching signal, 11... Driver circuit, 12... Signal transmission circuit. −＋− [Representative Patent Attorney Masao Ogawa゛, -1-1゜Compilation 1
Fig grass 2 days stem 3 days Y 4 times broom 6 mouths

Claims (1)

[Claims] 1. In a motor drive circuit for a refrigeration system, which includes a compressor motor driven by a commercial power supply or an inverter circuit, a switching means for switching between the commercial power supply or the inverter circuit, and a control unit for controlling switching of the switching means. , the control unit controls the switching means so that, when switching the switching means from the commercial power supply to the inverter circuit, the motor is driven by the commercial power supply for a predetermined time or more before the switching. Motor drive circuit for refrigeration equipment.