JPS622891Y2 - - Google Patents

Description

[Detailed description of the invention] The present invention relates to a device for protecting a refrigerator motor by detecting abnormalities in a motor drive circuit over a long period of time and stopping the drive of the motor if an abnormality occurs more than a predetermined number of times.

Refrigerators are equipped with a protection circuit to protect the motor from excessive load, and when the circuit is activated, the refrigerator stops operating and an abnormality is displayed. Moreover, the protection circuit is designed to operate even in the event of a power outage. Once the refrigerator motor stops, even if the cause of the protection circuit activation resolves naturally, it will not restart unless an administrator operates it. Therefore, constant monitoring was required, which was a major inconvenience for management.

Incidentally, the following two points are considered to be the main causes of motor overload.

A Phase loss due to poor connection to the commercial power supply, etc. B Motor load fluctuation A phase loss detection relay is installed in the protection circuit in case of phase loss in A, and a thermal relay is installed in case of overload due to load fluctuation in B. , it is necessary to interrupt the motor drive circuit by operating each relay. Among these overload causes, load variation B may occur when the temperature inside the refrigerator is high at the beginning of the refrigeration operation.
However, in this case, the load can often be reduced by restarting the refrigeration operation after a temporary stop. Therefore, even if an overload occurs, it is not necessary to completely stop the refrigeration operation.

For this reason, a control device has been devised that uses a timer and an electric circuit to restart the motor drive circuit after a predetermined period of time has elapsed even after the motor drive circuit is cut off due to overload during startup. However, this conventional control device restarts the refrigeration equipment after a predetermined period of time if an abnormality occurs due to an overload when starting up the refrigeration equipment.
Alternatively, maintenance over a long period of time, such as overnight, is impossible, and a device that can control abnormalities in the motor drive circuit over a long period of time has been desired.

Therefore, the present invention temporarily stops the motor when the detection section in the motor protection circuit is activated while the refrigerator is operating, but restarts the motor after a predetermined period of time has passed after the detection section returns, and the number of times the motor is stopped is set. It is an object of the present invention to provide a motor protection device for a refrigerator that completely shuts off the motor drive circuit when the number of times the motor drive circuit reaches the specified number of times and maintains that state, thereby making it possible to monitor abnormalities in the motor drive circuit over a long period of time. be.

This will be explained below with reference to the drawings. FIG. 1 shows a motor drive circuit to which the present invention is applied. Reference numerals 1, 2, and 3 are three-phase power input terminals connected to a motor 6 via a thermal relay 4 and a motor starting magnetic relay 5. The thermal relay 4 consists of a bimetal normally closed contact 7 and heat generating parts 8, 9, and the motor starting magnetic relay 5 consists of a magnet 10 and contacts 11, 12, 13. The normally closed contact 7
and magnet 10 and motor starting switch 14
are connected in series between the power supply terminals. In addition, a relay 15 for detecting an open phase is connected between the power terminals 1 and 3, and a relay 16 for detecting an open phase is connected between the power terminal 1 and the back of the contact 7 of the thermal relay.
7 and 18 (detection switches) are each connected to the circuit of the open phase alarm lamp 19.

When the motor start switch 14 is closed, the magnetic relay 5 is activated, each contact is closed, and the motor 6 is started. The motor load becomes too heavy and the heat generating parts 8, 9
When the metal generates heat, the bimetal senses it and contacts 7 open.
At this time, even if the motor drive switch 14 is closed, the magnet 10 is demagnetized and the magnet relay 5 is demagnetized.
The contacts 11, 12, 13 open and the motor stops. In addition, the circuit of the open-phase detection relay 16 is also cut off, the contact 18 enters the state shown in the figure, and the lamp 19 is lit to issue an alarm. In addition, the relay 15 for detecting phase loss,
When the three-phase power supplies 1, 2, and 3 are energized, the contacts 17 and 18 of 16 move to the left side from the illustrated state and open due to the operation of the open phase detection relays 15 and 16, and the lamp Lights out at 19.

Further, if a connection failure occurs between the motor and the three-phase power supply, one or both of the relays 15 and 16 is activated, the contact 17 or 18 is closed, and the lamp 19 is turned on. Also, in the event of a power outage, contacts 17 and 18
closes and the lamp lights up. Therefore, the relay 16 is
It operates in response to both power supply abnormalities and motor overload abnormalities.

FIG. 2 shows a refrigerator protection device consisting of the motor drive circuit A of FIG. 1 and a control circuit B for controlling the drive circuit A, and the same parts as in FIG. 1 are designated by the same reference numerals. Phase loss detection relay 1 of motor drive circuit A
Contacts 17 and 18 of 5 and 16 are connected to an input terminal 20 of control circuit B. This control circuit also connects main switch SW1 to battery C or power supply.
A power terminal 21 is connected to the power supply terminal 21, and a terminal 2 is connected to the main switch SW1 through the operation switch SW2 for stopping the motor 6.
2 and a terminal 23 to which a relay 100 for controlling the motor starting switch 14 is connected, and both terminals 2
A relay contact 24 is connected between 2 and 23, and the contact 24 is normally closed, and the motor 6 can be stopped by opening the contact 24.

When the motor drive circuit A detects an abnormality and the contact 17 or 18 of the open phase detection relay 15 or 16 closes, current flows from the power supply terminal 21 to the ground via the resistor, causing the base current of the transistor 25 to flow. Transistor 25 turns on. As a result, a collector voltage is generated, which charges the capacitor 27 via the resistor 26, thereby increasing the terminal voltage of the capacitor 27. The terminal voltage of this capacitor 27 passes through a resistor 28 and reaches a converter 29. When the voltage rises above the input detection voltage of the converter 29, the converter 29 is activated and the voltage at the output terminal becomes the power supply voltage (hereinafter referred to as H).
level) to a zero voltage level (hereinafter referred to as L level). This change is caused by the converter 30
The output changes from L level to H level. Note that the output of the converter 30 is fed back to the converter 29 through a resistor 31 to speed up the conversion and increase reliability. Further, the resistor 32 is for discharging the charge in the capacitor 27 when the abnormal state returns to the normal state and the transistor 25 is turned off.
A sustain circuit D is formed by resistors 26, 3
2. Due to the time constant of the capacitor 27, the converter 29 is not inverted for a predetermined period of time even after the transistor 25 is turned off.

The output of the converter 30 is connected to an OR circuit 33, and when the output becomes H level, the output of the OR circuit 33 also becomes H level, turning on the transistor 34. As a result, the relay 35 is energized, and the contact 2
Open 4. Therefore, the motor 6 stops. When the abnormality in motor drive circuit A is resolved and contact 17 or 18 opens, transistor 25 is turned off, and the charge in capacitor 27 is gradually discharged via resistors 26 and 32 of sustain circuit D, for a predetermined time determined by a time constant. After a lapse of time, the output of converter 29 becomes H level, thereby the output of converter 30 becomes L level, and the output of OR circuit 33 also becomes L level. Therefore, transistor 34 is turned off, relay 35 is demagnetized, contact 24 is closed, relay 100 is energized and motor start switch 14 is closed, so motor 6 is started again.

On the other hand, the H level of the output of the converter 29 is sent to the AND circuit 36, and the AND circuit 36 is connected to the terminal 23.
Since the contact 24 is closed after a predetermined period of time has elapsed, an H level signal is sent to the AND circuit 36, and therefore an H level output is sent from the AND circuit 36 to the counter circuit 37. The counter circuit 37 is an FF (flip-flop) 3
When the input signal from the AND circuit 36 is counted three times by a synchronous counter composed of 8, FF 39, and NAND 40, the output of NAND 40 changes to L level. That is, each time the motor drive circuit A detects an abnormality and stops driving the motor 6, the counter circuit 37 advances, and when this abnormality is counted three times, the output of the NAND 40 changes from the H level to the L level.

The output of the NAND 40 is sent to a flip-flop circuit 41 which is a holding circuit, and when the input of the flip-flop circuit 41 becomes L level, the output terminal 42 becomes H level. The flip-flop circuit 41 is for holding the input signal, so even if the input changes to H level after the output changes to L level,
Furthermore, even if the output goes to L level, the output remains unchanged. The output of the flip-flop circuit 41 is H.
When the level is reached, the transistor 43 is turned on, and a lamp 44, which is an example of an alarm device, lights up to warn that the operation of the motor drive circuit A has been stopped. At the same time, the output of flip-flop 41 is connected to OR circuit 3.
3, the transistor 34 of the motor stop circuit 101 is turned on, and the contact 24 is opened by the relay 35. Therefore, relay 100 is demagnetized and motor start switch 14 is opened as shown, stopping motor 6 as described above. A signal from the flip-flop circuit 41 is input to this OR circuit 33, and since this flip-flop circuit 41 maintains its output at the H level as described above, the motor 6 cannot be used for maintenance or repair. It will continue to stop until it is reset again. A reset circuit 45 is used to set the counter circuit 37 and the flip-flop circuit 41 to their initial states when the circuit is energized.

Next, FIG. 3 is a timing chart showing the operation of this embodiment. This graph shows, for example, the control of motor 6 over a long period of time (such as 24 hours), and the motor start switch 1
4 shows the operation under each condition from turning on to turning off. FIG. 3A shows a case where an abnormality in the motor drive circuit A is detected twice between the on and off of the switch 14. In this case, after the contact 17 or 18 of the open phase detection relay 15 or 16 is turned on, When the time T has elapsed, the motor 6 is restarted and continues to operate until the switch 14 turns it off. B and C in Figure 3 are both switch 1
This shows a case where an abnormality is detected three times while the motor 4 is turned on and off, and when the third abnormality occurs, the transistor 34 remains on and the motor 6 remains stopped. At the same time, the lamp 44 lights up to warn that the motor 6 is stopped. The time at which an abnormality occurs in both B and C is random, and the interval t ₁ at which the contact 17 or 18 of the open phase detection relay 15 or 16 is turned on is
_-t6 are all different, and therefore, the timing at which the motor 6 stops after three abnormalities occur is an uncertain timing.

As is clear from the above, according to the configuration of the present invention,
When the motor drive circuit detects an abnormality, the motor is temporarily stopped, and even when an abnormality occurs in the power supply, the motor is immediately stopped before an overload occurs on the motor, but once the abnormality is resolved, the motor is restarted. Starts and protects the motor.

Then, the number of times the motor stops is counted, and when the set number of times is reached, the motor is completely stopped.This ensures that the motor stops completely even if the intervals between abnormal conditions are irregular or long. obtain.

Therefore, even if an abnormality occurs at an unexpected time, such as when operating a refrigerator for a long time all day and night, the motor can be temporarily stopped and the abnormality is resolved (even if it is not actually resolved). By restarting the motor (if it returns to normal), you can buy time for the motor to completely stop, allowing you to operate the motor without freezing for a long time and avoid overloading the motor under abnormal conditions. Can be maintained. Therefore, the administrative effort can be simplified, and special effects such as enabling unmanned operation at night can be obtained.

[Brief explanation of the drawing]

Figure 1 shows a motor drive circuit to which the present invention is applied.
Figure 2 is a circuit diagram of the motor protection device according to the present invention.
FIG. 3 is a timing chart showing the operation under each condition of this embodiment. 1, 2, 3...Input terminal, 4...Thermal relay, 5...Magnetic relay, 6...Motor,
8, 9... Heat generating part, 15, 16... Phase loss detection relay, 21... Power supply terminal, 37... Counter circuit, 41... Flip-flop circuit.

Claims (1)

[Scope of utility model registration request] An open-phase detection relay is connected between the power supply terminals, and another open-phase detection relay is connected between the power supply terminal and the back of the thermal relay contact. A detection switch that detects an abnormality and generates a signal, a sustaining circuit that outputs a signal for a predetermined time after the detection switch completes its operation, and a counter circuit that counts the number of times the signal is received from the sustaining circuit and generates an output signal when the number of times exceeds a set value. and,
a holding circuit that holds the output signal of the counter circuit; an OR circuit that operates based on either the output signal of the holding circuit or the output signal of the sustaining circuit; and a motor stop circuit that operates based on the output signal of the OR circuit; The alarm device is activated by the output signal of the holding circuit, and when an abnormality occurs in the motor drive circuit, the motor is stopped for a predetermined period of time and then restarted, and when this abnormality occurs a predetermined number of times, the motor is stopped. A refrigerator motor protection device that prevents restarts.