JPH06201733A - Electric current sensor for both ac and dc - Google Patents

Abstract

PURPOSE:To provide an electric current sensor capable of detecting both AC and DC. CONSTITUTION:When an current Io flows in a coil N3 under a state where an excitation signal is being fed from a high frequency signal generating circuit 1 to a coil N1, a saturable magnetic substance core 2 is saturated, the excitation signal of the coil N1 is not transmitted to a coil N2 side, input V1 of an on- delay circuit 5 becomes smaller than a threshold value VTH, and output Vo of the on-delay circuit 5 is stopped. On the other hand, when the current Io is not applied, the excitation signal of the coil N1 is transmitted to the coil N2 side, an input level of the on-delay circuit 5 exceeds the threshold value VTH and when it is continued for a specified time or more, the output Vo is generated. Change of the input level of the on-delay circuit 5 due to an amplitude change of an AC can be absorbed by delaying action of the on-delay circuit 5 so that detection of the AC can be attained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alternating current / direct current sensor.

[0002]

2. Description of the Related Art In a work system using an industrial machine, such as a robot, for example, to drive a robot for a program input (teaching) or maintenance to the robot. There are cases where a worker approaches a robot to perform work while the power is on. At this time, if a motor current erroneously flows through a robot moving part, for example, a driving motor of the robot arm, and the robot arm operates, a very dangerous state occurs for an operator.

Therefore, the motor current of the drive motor of the robot movable part is monitored, and if the motor current flows while the worker is performing the above-mentioned work, the main drive power source of the robot is immediately cut off. Interlock system
A current sensor is used as a sensor for monitoring the motor current, which is indispensable for ensuring the safety of workers.

The present invention has been made in view of the above circumstances, and an object thereof is to provide a current sensor capable of detecting both an alternating current and a direct current.

[0005]

Therefore, in the current sensor of the present invention, the three windings of the first winding, the second winding and the third winding are wound, and the third winding is detected. A saturable magnetic core that becomes saturated when a current flows, a high-frequency signal generation circuit that supplies a high-frequency excitation signal to the first winding, and a second winding connected to the second winding An ON-delay circuit that generates an output when the received signal level is maintained at a predetermined value or higher for a predetermined time, and the presence or absence of a detected current in the third winding is detected by the output state of the ON-delay circuit. And

The excitation signal supplied to the first winding and the detected current flowing in the third winding are synchronized. Further, by making the drive power supply of the high-frequency signal generation circuit that generates the excitation signal the same as the power supply for supplying the detected current, the excitation signal supplied to the first winding and the power supply flowing to the third winding are supplied. The detection current is synchronized.

[0007]

In this structure, when a high-frequency excitation signal is supplied from the high-frequency signal generating circuit to the first winding, the saturable magnetic core will not be in a saturated state when no current flows in the third winding. The excitation signal supplied to the first winding is transmitted to the second winding side. In this case, the output level of the second winding input to the on-delay circuit becomes equal to or higher than a predetermined value, and when the state of being equal to or higher than the predetermined value continues for a predetermined time, an output is generated from the on-delay circuit and a current flows to the third winding. Can know that is not flowing.

On the other hand, when a current flows through the third winding, the saturable magnetic core is saturated and the excitation signal supplied to the first winding is not transmitted to the second winding side. Therefore, when the output level of the second winding input to the on-delay circuit decreases and becomes smaller than a predetermined value, the output of the on-delay circuit stops and it can be known that the current has flowed to the third winding. it can.

When the detected current flowing in the third winding is an alternating current, the current periodically becomes zero level, and at this time,
Although the excitation signal of the first winding is transmitted to the second winding side and the input level of the on-delay circuit exceeds a predetermined value,
No output is generated immediately due to the delay operation of the delay circuit. Then, the current to be detected in the third winding rises after passing the zero level point, so that the input level of the on-delay circuit rises and exceeds the predetermined value. This operation is repeated every half cycle of the detected current. Therefore, by setting the delay time of the on-delay circuit to be longer than at least a half cycle of the current to be detected, it is possible to reliably detect the presence or absence of the current to be detected even when the current to be detected is alternating current. Both direct current can be detected.

If the excitation signal supplied to the first winding and the detected current flowing through the third winding are synchronized, the excitation signal also becomes zero level when the detected current is at zero level. Therefore, there is no increase in the output level on the second winding side when the detected current is at the zero level. Therefore, the delay time of the on-delay circuit can be shortened.

[0011]

Embodiments of the present invention will be described below with reference to the drawings. 1 and 2 show a first embodiment of this embodiment, and show an example in which the detected current is direct current. In FIG. 1 showing the configuration of the first embodiment of the present invention, a high frequency signal generation circuit 1 for generating a high frequency signal is driven by a DC power supply V _CC , and a saturable magnetic material is provided via a capacitor C and a resistor R. It is connected to the first winding N1 wound around the core 2. Around the saturable magnetic core 2, a second winding N2 is wound in addition to the first winding N1, and a third winding N3 connected to a load 3 to be monitored for the presence or absence of current supply. And constitutes a sensor section. The second winding N2 is connected to the on-delay circuit 5 via the rectifier circuit 4. When the rectified output from the rectifier circuit 4 corresponding to the output generated in the second winding N2 is equal to or more than a predetermined value, the on-delay circuit 5 continues the rectified output at a level equal to or more than the predetermined value for a predetermined time. When a rectified output with a level higher than a predetermined value is input, the output is generated with a predetermined delay time, which has both a level verification function and a delay function, and has a failure. It is a conventionally known fail-safe device that does not sometimes generate an output. In the figure, 6 indicates a load drive switch.

Next, the operation of the current sensor of the first embodiment will be described.
The work will be described based on the time chart of FIG. high frequency
The high frequency signal generated by the signal generating circuit 1 is a capacitor C
And the first winding as an excitation signal of the sensor unit via the resistor R.
Supplied to N1. In this state, the load 3
Load current I₀Winding is not flowing, the first winding
The excitation signal supplied to N1 passes through the core 2 to the second winding N
2 is transmitted to the second side and corresponds to the excitation signal on the second winding N2.
High frequency output is generated. This high frequency output is the rectifier circuit 4
Is rectified by the rectified output V_iIs the on-delay circuit 5
To enter. In this case, the rectified output V_i
Is the threshold level V of the on-delay circuit 5. _THSince
Will be on top. Load current I₀Does not flow as it is,
Bell V_THRectified output V above_iOn delay
Delay time T of circuit 5_DOn delay
Output V from circuit 5_oOccurs (corresponds to high energy state
Output of logical value 1) and load current I₀Is not flowing
You can know.

On the other hand, when the load current I ₀ flows through the third winding N3 while the excitation signal is flowing through the first winding N1, the saturable magnetic core 2 is saturated and the excitation signal becomes the second It is not transmitted to the winding N2 side. Therefore, the second winding N2
The output decreases, and the level of the rectified output V _i from the rectifier circuit 4 decreases and becomes lower than the threshold level V _TH of the on-delay circuit 5. Then, when the rectified output V _i becomes lower than the threshold level V _TH , the output V _o of the on-delay circuit 5 stops (output of a logical value 0 corresponding to the low energy state), and the load current I ₀ becomes. You can know what is flowing.

Therefore, if the load current is monitored using such a current sensor and the driving power source of the load 3 is shut off when the output V _o of the on-delay circuit 5 is stopped, the load 3 is supplied with the current. When it flows, the load drive power supply can be automatically shut off, and the safety of the operator can be secured when carrying out work such as program input and maintenance of the robot with the main power supply of the robot turned on. .

The on-delay circuit 5 is constructed so that the output V _o is not generated when the on-delay circuit 5 fails, and the load 3
It is a fail-safe configuration because the power supply for driving is automatically stopped. Next, a second embodiment of the current sensor of the present invention is shown in FIGS. This is an example in the case where the monitored load current flowing through the load 3 is AC. The same parts as those in the first embodiment are designated by the same reference numerals and the description thereof will be omitted.

In FIG. 3, in the present embodiment, the driving power of the high frequency signal generating circuit 1 is obtained by obtaining the AC output from the AC power supply 11 by the output from the full-wave rectification circuit 12. Further, an alternating current is supplied to the load 3 from an alternating current power supply 13. Other configurations are similar to those of the first embodiment.
Of course, the high frequency signal generating circuit 1 may be directly driven by a DC power source as in the first embodiment.

Next, the operation of the current sensor of the second embodiment will be described with reference to the time chart of FIG. High frequency signal generation circuit 1 from AC power supply 11 via full wave rectification circuit 12
When drive power is input to the high-frequency signal generation circuit 1, the high-frequency signal generation circuit 1 is driven to supply the high-frequency signal to the first winding N1 via the capacitor C and the resistor R as an excitation signal for the sensor unit. In this state, when the AC load current I ₀ as the current to be detected does not flow in the load 3, the first
The excitation signal supplied to the winding N1 is transmitted to the second winding N2 side, and the rectified output V of the high frequency output generated in the second winding N2
_i is input to the on-delay circuit 5. This rectified output V
The level of _i is the threshold level V _TH of the on-delay circuit 5.
As described above, when the load current I ₀ does not flow as it is and the delay time T _D of the on-delay circuit 5 or more elapses, the output V _o is generated from the on-delay circuit 5 (output of logical value 1 corresponding to high energy state). However, it can be known that the load current I ₀ is not flowing.

On the other hand, an excitation signal is flowing in the first winding N1.
Load current I to the third winding N3₀Flows
And as shown in FIG.₀AC waveform of
According to the rectified output V input to the ON-delay circuit 5_oBut
Change. That is, the load current I ₀From positive to negative, negative to positive
Near the switching zero point, the load current I₀Hardly flows,
Flow output V_iIs the threshold level V of the on-delay circuit 5_THSince
Above, in other areas rectified output V_iIs On Day
Threshold level V of the delay circuit 5_THWill be lower. Load current I
₀This state will be repeated while is flowing.
It However, in the on-delay circuit 5, the threshold level V
_THRectified output V above_iIs the delay of the on-delay circuit 5
Interval T_DOutput V if not continued for a predetermined time corresponding to_oBut
Does not occur. Where rectified output V_oIs the load current I₀of
About half cycle (T / 2, T is load current I₀Every cycle)
.Threshold level V of the delay circuit 5_THThat is all. Obey
The delay time T of the on-delay circuit 5_DAt least
Load current I₀If it is longer than the half cycle of₀But
Output V from the on-delay circuit 5 while flowing _o
Stops and the load current I₀To know that is flowing
Yes, AC load current I₀However, it can be detected.

Therefore, according to these current sensors of this embodiment, the load current I ₀ can be detected regardless of whether the load current I ₀ is DC or AC. In addition, in the current sensor shown in FIG.
The driving AC power supply 11 for the high-frequency signal generation circuit 1 and the driving AC power supply 13 for the load 3 are shared, and the excitation signal supplied from the high-frequency signal generation circuit 1 to the first winding N1 and the load current I flowing through the load 3 _With the configuration in which ₀ and ₀ are synchronized, the load current I ₀
When the load current I ₀ flows, there is no period during which the rectified output V _i of the second winding N2 becomes _{equal to} or higher than the threshold level V _TH of the on-delay circuit 5 because the excitation signal disappears. The delay time T _D of the delay circuit 5 can be set extremely short.

[0020]

As described above, according to the present invention, an on-delay circuit is provided on the detection signal output side of the sensor section for detecting current by utilizing the magnetic saturation of the saturable magnetic core. Therefore, it is possible to detect both direct current and alternating current with a single sensor, which makes the sensor device common and extremely convenient.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a first embodiment of the present invention.

FIG. 2 is a time chart showing the relationship between the load current and the input and output of the on-delay circuit according to the first embodiment.

FIG. 3 is a circuit diagram showing a second embodiment of the present invention.

FIG. 4 is a time chart showing the relationship between the load current and the input and output of the on-delay circuit according to the second embodiment.

[Explanation of symbols]

 1 High-frequency signal generation circuit 2 Saturable magnetic core 5 On-delay circuit

Claims (3)

[Claims] 1. A saturable magnetic core that is wound when three windings of a first winding, a second winding and a third winding are wound, and becomes saturated when a current to be detected flows through the third winding. A high-frequency signal generation circuit for supplying a high-frequency excitation signal to the first winding, and a reception signal level received by the second winding connected to the second winding is equal to or higher than a predetermined value and continued for a predetermined time. An alternating current / direct current sensor, comprising an on-delay circuit for generating a time output, and detecting the presence or absence of a detected current in the third winding based on the output state of the on-delay circuit. 2. The alternating current / direct current sensor according to claim 1, wherein the excitation signal supplied to the first winding and the detected current flowing in the third winding are synchronized with each other. 3. The AC / DC current sensor according to claim 2, wherein the drive power source of the high frequency signal generating circuit for generating the excitation signal and the power source for supplying the detected current are the same.