JP2517446Y2 - Air source device protection circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to an induction motor driven air source device for general industrial use or railway vehicles, and in particular, protection against a failure of a light load valve for starting an induction motor. This is an improved circuit.

[Prior Art] FIG. 3 is an example of a circuit configuration of a conventional air source device of this type (Japanese Patent Laid-Open No. 63-134360). In the figure, 1 indicates the entire air source device. Reference numeral 2 is an air source, which is configured by connecting an air compressor 7 driven by an induction motor 6, aftercoolers 12 and 13, a check valve 8, a safety valve 14, an air reservoir 10 and a light load valve 11 as shown in the figure. Has been done. With such a configuration, when the main circuit electromagnetic contactor 5 is turned on and the electric motor 6 and the air compressor 7 are operated, the air discharged from the compressor 7 is aftercooled.
12, the discharge pipe 9, the aftercooler 13 and the check valve 8 are sent to the air reservoir 10 to accumulate the pressure.

Reference numeral 3 denotes a control circuit, which is constituted by connecting a pressure adjusting pressure switch 15, an exciting coil 16 of the electromagnetic contactor 5, and a control relay 17 of the light load valve 11 as shown in the drawing. In addition, 18 is an auxiliary power switch. With such a configuration, when the pressure in the air reservoir 10 rises to the upper limit set value of the pressure switch 15, the contact 15b of the pressure switch 15 is turned off, the excitation of the exciting coil 16 is cut off, and the electromagnetic contactor 5 is shut off. Then, the electric motor 6 and the compressor 7 are stopped. When the pressure of the air reservoir 10 drops to the lower limit set value of the pressure switch 15, the contact 15b is turned on, the exciting coil 16 is excited, the electromagnetic contactor 5 is turned on, and the electric motor 6 and the compressor 7 are operated. It

In this way, the operation stop is controlled to be alternately repeated, and as a result, the pressure of the air reservoir 10 is constantly regulated between the upper limit setting value and the lower limit setting value of the pressure switch 15.
At the same time as exciting the exciting coil 16, a relay for controlling the light load valve
17, the light load valve 11 is switched from the exhaust position a to the closed position b. Therefore, during the operation of the compressor 7, the discharge air is sent to the air reservoir 10 without leaking from the light load valve 11.
Also, at the same time that the exciting coil 16 is degaussed, the relay 17 is also degaussed,
The light load valve 11 switches from the closed position b to the exhaust position a.
Therefore, the compressed air in the discharge pipe 9 is exhausted through the light load valve 11 while the compressor 7 is stopped. As a result, the load of the compressor 7 becomes light, and the next time the electric motor is started, the electric motor 6 can be smoothly started without burning.

Reference numeral 4 denotes a protection circuit, which is configured by connecting a protection pressure switch 19, a contactor interlocking relay 20, a protection relay 22, a timer 21, and a reset switch 29 as shown in the figure. Reference numeral 23 is a throttle for preventing pressure fluctuation. With such a configuration, while the compressor 7 is operating, the light load valve control relay 17 is excited, so that the light load valve 11 is in the closed position b.
Therefore, the pressure of the discharge pipe 9 is almost the same as the pressure of the air reservoir 10. Therefore, the pressure switch 19 detects that the pressure in the discharge pipe 9 is equal to or higher than the set pressure, and the contact 19a is turned on.

However, at this time, the contactor interlocking relay 20 is excited, its contact 20b is turned off, and the circuit of the protection relay 22 is opened. It is in a state. When the compressor 7 is stopped in this state, the relay 20 is demagnetized and its contact 20b is turned on. As a result, the timer 21 starts measuring time.
At this time, if the light load valve 11 is normal, the light load valve control relay 17 is also demagnetized, so that the closed position B is switched to the exhaust position B. Then, the pressure air in the discharge pipe 9 is exhausted from the light load valve 11, and the pressure in the discharge pipe 9 is reduced.

Then, when the pressure in the discharge pipe 9 becomes equal to or lower than the set pressure of the pressure switch 19, the contact 19a is turned off and the time measurement of the timer 21 is interrupted. Therefore, when the light load valve 11 is normal, the protection relay 22 is not excited and does not operate.

However, the pressure in the discharge pipe 9 does not decrease to the set pressure of the pressure switch 19 unless the light load valve 11 fails and the closed position B is switched to the exhaust position B. Therefore, the contact 19a remains on and does not turn off even if the set time of the timer 21 elapses.Therefore, the timer 21 operates, the protection relay 22 is excited, the contact 22a turns on, and self-holding is performed. To be done. As a result, the contact 22b is turned off and the circuit of the exciting coil 16 of the electromagnetic contactor 5 is opened. Therefore, when the light load valve 11 is out of order, the electromagnetic contactor 5 is kept in the disconnected state, so that the electric motor 6 is not started and the heavy load is prevented from starting and burning. Is protected.

When the protection relay 22 is energized and activated, its contact 22
Since a is turned on and self-holding is performed, when the operation of the compressor 7 is restarted, the reset switch 29 is pressed to reset the operation.

[Problems to be solved by the invention] In the conventional protection circuit, the timer time is shortened due to chattering of the pressure switch, or the set value of the pressure switch is changed to a lower value, or some other reason. When the protection circuit malfunctions due to a cause, the electromagnetic contactor 5 is not turned on and is not turned on. Therefore, the compressor 7 remains stopped, and this state is maintained unless reset. Therefore, in the case of railway vehicles, the air source may be insufficient, which may hinder vehicle operation. In addition, in recent years, due to the development of electronic technology, inverter control, star delta control, etc. have been performed, and the device has become complicated.
If the electric motor 6 does not start, it may be due to a failure of these control systems,
There is a problem that it is difficult to find out whether the failure is in the air piping system, and it is difficult to find the failure location.

[Means for Solving Problems] The first invention is intended to solve the above problems, and therefore discharge air of an air compressor driven by an induction motor is stored in an air reservoir. The pressure is accumulated, the pressure of the air reservoir is detected by a pressure control pressure switch, and the electromagnetic contactor for the main circuit of the induction motor is on / off controlled so that the pressure of the air reservoir is within a predetermined range. An air source device configured to open the light load valve to discharge the air in the discharge pipe of the air compressor into the atmosphere while the electric motor is stopped, and includes a protective pressure switch for detecting the pressure in the discharge pipe. When the electromagnetic contactor is off and the protection pressure switch detects a pressure higher than a set pressure,
A protective relay is operated to disconnect the exciting circuit of the electromagnetic contactor and to issue an alarm.

According to a second aspect of the present invention, in the same air source device as described above, the same protective pressure switch as that described above is provided, the electromagnetic contactor is turned off, and the protective pressure switch is at a set pressure or higher. A protective relay that operates when pressure is detected,
A rotary relay that stores the number of operations of the protection relay, operates when the number of times reaches a set number, and holds the protection relay by itself, and disconnects the excitation circuit of the electromagnetic contactor by the operation of the protection relay. At the same time, an alarm is issued by the operation of the protection relay or the rotary relay.

[Operation] In the first invention, while the protection relay is operating (while the pressure of the discharge pipe is higher than the set pressure), the circuit of the exciting coil of the electromagnetic contactor is disconnected, and the electric motor is in a heavy load state. Protected from starting with. And the discharge pipe pressure drops,
When the protection relay is restored, the electromagnetic contactor is turned on and the compressor automatically operates without pressing the reset switch. Therefore, the shortage of the air source as in the conventional case does not occur.

Further, in the second invention, since the protection relay self-holds when the protection relay has operated the set number of times, the protection relay operates in the same manner as the first invention until the set number of times is reached. Even if the discharge pipe pressure falls below the set pressure of the protection pressure switch and the load becomes light, the motor can be started automatically, so it is possible to prevent burnout when starting the motor and prevent shortage of the air source. Becomes If the protective pressure switch or the like malfunctions, the compressor operates without problems. If the light load valve system actually fails, the discharge pipe pressure rises when the compressor is operated, so the protection relay operates again and the above-described operation is performed. Such operation occurs every time the compressor is operated. When the number of operations of such a protection relay reaches the set number of times of the rotary relay, it can be regarded as a true light load valve failure, so the protection relay is self-held and the motor and compressor are reset.
Continue to stop. In this way, when the rotary relay reaches the set number of times and the protection relay operates, it is considered as a light load valve system failure by self-holding for the first time.Therefore, even if the protection pressure switch malfunctions, the protection relay does not self-hold. This is a highly accurate fault detection compared to the conventional case in which it is held. Therefore, the alarm generated by this self-holding ensures that the driver knows that the light load valve system is out of order, and immediately takes action to reset and restart the operation.

[Embodiment] FIG. 1 is a circuit configuration diagram of a first embodiment of an air source device according to the present invention. In the figure, the same parts as those of FIG. 3 showing the conventional example are designated by the same reference numerals, and the description thereof will be omitted.
Reference numeral 31 is an indicator light that indicates that the protection relay 22 has operated, and for example, an alarm device such as a buzzer may be used. In short, this embodiment uses the conventional timer shown in FIG.
21, remove the reset switch 29, provide an indicator light 31,
In FIG. 3, the contact 22 used for self-holding of the protection relay 22.
a is connected in series with the indicator light 31 so as to form a circuit of the indicator light 31 when the protection relay 22 operates.

With the above configuration, when the compressor 7 is operated and the pressure in the air reservoir 10 rises to the upper limit set value of the pressure adjusting pressure switch 15, the contact 15b of the pressure switch 15 is opened and the electromagnetic contactor 5 is opened.
Since the exciting coil 16 of is demagnetized, the electric motor 6 is stopped,
The compressor 7 stops accumulating pressure in the air reservoir 10. At the same time, the light load valve control relay 17 is demagnetized, so that the light load valve
11 is switched from the closed position b to the exhaust position b, and the discharge pipe 9
The air inside is released into the atmosphere. As a result, the compressor 7 becomes lightly loaded and can be started at the next start without burning the electric motor.

As described above, when the light load valve 11 is operating normally, the pressure in the discharge pipe 9 of the protection pressure switch 19 becomes equal to or lower than the set pressure, so that the contact 19a is opened and the protection relay 22 does not operate. Then, when the pressure in the air reservoir 10 decreases and reaches the lower limit setting value of the pressure adjusting pressure switch 15, the pressure switch
The contact 15b of 15 is closed and the exciting coil 16 of the electromagnetic contactor 5 is excited, so that the electric motor 6 is started. At the same time, the light load valve control relay 17 is also excited, so that the light load valve 11 switches from the exhaust position a to the closed position b and disconnects from the atmosphere, so that the air reservoir 10 accumulates pressure by the compressor 7. Be started. Further, since the contactor interlocking relay 20 is also excited at the same time, the contact 20b is turned off, and the protection relay 22 remains demagnetized and does not operate.

The above is the operation of the air source device when the light load valve 11 is normal. However, when the light load valve 11 fails after the compressor 7 is stopped and the pressure air in the discharge pipe 9 is not released into the atmosphere, the pressure in the discharge pipe 9 is higher than the set pressure of the pressure switch 19, so the contact Since 19a is closed and the contact 20b is also closed at this time (when the compressor 7 is stopped), the protective relay 22 is excited and operates. As a result, the contact 22b of the circuit of the exciting coil 16 is opened. Therefore, even if the pressure of the air reservoir 10 drops to the lower limit set value and the contact 15b of the pressure adjusting pressure switch 15 is closed, the electric motor 6 does not start. Therefore, the electric motor 6 is protected from being burned out when it starts under heavy load. If the operation of the protection relay 22 is due to an erroneous detection of the pressure switch 19 or the like, and the pressure of the discharge pipe 9 automatically drops below the set pressure of the pressure switch 19, the contact 19a is opened to protect it. When the relay 22 is demagnetized, the contact 22b is closed, the electromagnetic contactor 5 can be closed, and the contact 15b of the pressure switch 15 is closed, the compressor 7 is automatically operated. Therefore, the shortage of the air source as in the conventional case can be eliminated. Further, when the protection relay 22 is operated, the contact 22a is closed and the indicator light 31 is turned on, so that the driver can easily know that the light load valve 11 system is in failure, and thus even in the case of failure, No longer left alone for long periods.

FIG. 2 is a circuit configuration diagram of the second embodiment according to the present invention. In the figure, those parts which are the same as those corresponding parts in FIGS. 1 and 3 are designated by the same reference numerals, and a description thereof will be omitted. 29 is a reset switch, 30 is a timer, 40 is a timer relay that operates after a set time of the timer 30 from the time of input, 50 is a rotary relay that stores the number of inputs and operates when the number of times reaches the set number. is there.

That is, in this embodiment, a timer 30 and a timer relay 40 are provided in the circuit of the first embodiment shown in FIG. 1, and the protection relay is delayed by the set time T of the timer 30 when the pressure adjusting pressure switch 15 is turned off. 22 circuit is closed by contact 40a,
In addition, the signal when the protection relay 22 is operating is sent to the contact 22a.
To input to the rotary relay 50, count the number of inputs to the rotary relay 50, and when the number of times of setting of the rotary relay 50 is reached, operate the rotary relay 50 and connect the protection relay 22 and the rotary relay 50 with the contact 50a. The indicator lamp 31 is self-held and the indicator lamp 31 is turned on.

With the above configuration, when the upper limit setting value of the air reservoir 10 is raised and the electromagnetic contactor 5 is shut off, the contactor interlocking relay 20 is also demagnetized at the same time and the contact 20b is closed, but the timer relay 40 is It does not work because it is delayed by the timer 30.

When the set time T of the timer 30 has elapsed, the timer relay 40 is excited and the contact 40a is closed. At this time, if the light load valve 11 fails and the pressure in the discharge pipe 9 does not drop, the contact 19a of the pressure switch 19 is closed, so the protection relay 22
Is excited and the exciting circuit of the electromagnetic contactor 5 is opened by the contact 22b, so that even if the pressure of the air reservoir 10 drops to the lower limit set pressure of the pressure switch 15, the electric motor 6 is protected without being started.

Then, when the light load valve 11 returns to normal due to some reason and the pressure in the discharge pipe 9 returns to a value equal to or lower than the set value of the pressure switch 19,
The contact 19a of the pressure switch 19 is opened, the protection relay 22 is demagnetized, the contact 22b is closed, and the motor 6 is automatically returned to the startable state. Therefore, the shortage of the air source as in the conventional case is eliminated.

The above operation is the same as that of the embodiment shown in FIG. But,
It is not preferable that the protection relay 22 repeatedly operates and returns too often because it may accelerate wear of the relay contact and the electromagnetic contactor contact. Therefore, in this embodiment, the rotary relay 50 is caused to count the number of operations of the protection relay 22,
When the set number of times is reached, it is regarded as a true failure detection, the protection relay 22 is held by itself, and the indicator lamp 31 is turned on.

That is, when the electromagnetic contactor 5 is turned on, the protection relay 22
The operation of the rotary relay 50 is input to the rotary relay 50 by closing the contact 22a.
When the set number of times is reached, the rotary relay 50 operates, the rotary relay 50 is self-held by the contact 50a, the protection relay 22 is also self-held, and the indicator lamp 31 is lit to notify the driver of the failure. When is repaired, the reset switch 29 is pressed to restore it.

In the second embodiment, the number of operations of the protection relay 22 is counted, and when the number of operations reaches the set number, the indicator lamp 31 is turned on. However, like the first embodiment, the protection is protected. The indicator lamp 31 may be turned on when the relay 22 operates.

[Advantages of the Invention] As described above, according to the invention of claim 1, the induction motor for starting the compressor is not driven (the electromagnetic contactor for the main circuit is off) and for protection. Even if the protective pressure switch malfunctions because the protective relay operates and disconnects the excitation circuit of the electromagnetic contactor when the pressure switch detects that the pressure in the discharge pipe is higher than the set pressure. Actually, when the pressure in the discharge pipe is less than the set pressure, the protection relay is restored, so that the electromagnetic contactor is turned on and the induction motor can be operated. Therefore, when the air source becomes insufficient, the pressure adjusting pressure switch that detects the pressure of the air reservoir operates to operate the induction motor, so that the compressor operates and air is accumulated in the air reservoir.
There is no shortage of air source. Further, when the protection relay operates, an alarm is also issued, so that it is possible to easily know that the light load valve system is out of order.

According to the second aspect of the invention, only when the operation of the protection relay as described above occurs a set number of times, the protection relay is held by itself and the excitation circuit of the electromagnetic contactor is maintained in the disconnected state. In addition, since it is configured to generate an alarm, the electric motor is stopped only when the light load valve system actually fails instead of malfunctioning of the protective pressure switch or the like. Therefore, only when the light load system actually fails, it is possible to prevent the electric motor from being burnt out due to the heavy load, and it is possible to notify that the light load valve system is broken. Further, in the case of malfunction of the protective pressure switch or the like, the shortage of the air source can be prevented in the same manner as in the invention according to claim 1.

[Brief description of drawings]

FIG. 1 is a circuit configuration diagram of a first embodiment of the present invention, FIG. 2 is a circuit configuration diagram of the second embodiment, and FIG. 3 is a circuit configuration diagram of a conventional air source device. 5 ... Electromagnetic contactor for main circuit, 6 ... Induction motor, 7 ...
Air compressor, 9 …… Discharge pipe, 10 …… Air reservoir, 11 …… Light load valve, 15 …… Pressure control pressure switch, 19 …… Protection pressure switch, 22 …… Protection relay, 31 …… Alarm, 50 ... Rotary relay.

Claims (2)

(57) [Scope of utility model registration request] 1. A discharge air of an air compressor driven by an induction motor is accumulated in an air reservoir, the pressure of the air reservoir is detected by a pressure adjusting pressure switch, and the pressure of the air reservoir becomes a pressure within a predetermined range. As described above, the main circuit electromagnetic contactor of the induction motor is controlled to be turned on and off, and the light load valve is opened to discharge the air in the discharge pipe of the air compressor to the atmosphere while the induction motor is stopped. In the air source device,
The electromagnetic contactor includes a protective pressure switch for detecting the pressure in the discharge pipe, and when the electromagnetic contactor is off and the protective pressure switch detects a pressure equal to or higher than a set pressure, a protective relay is operated. This is a protection circuit for the air source device that turns off the excitation circuit and issues an alarm. 2. The discharge air of an air compressor driven by an induction motor is accumulated in an air reservoir, the pressure of the air reservoir is detected by a pressure adjusting pressure switch, and the pressure of the air reservoir is within a predetermined range. The main circuit electromagnetic contactor of the induction motor is controlled to be turned on and off so that the light load valve is opened to discharge the air in the discharge pipe of the air compressor to the atmosphere while the induction motor is stopped. In the air source device,
A protective pressure switch for detecting the pressure in the discharge pipe, a protective relay that operates when the electromagnetic contactor is off and the protective pressure switch detects a pressure equal to or higher than a set pressure,
A rotary relay that stores the number of operations of the protection relay, operates when the number of times reaches a set number, and holds the protection relay by itself, and disconnects the excitation circuit of the electromagnetic contactor by the operation of the protection relay. At the same time, a protection circuit for the air source device which issues an alarm by the operation of the protection relay or the rotary relay.