JPS5926768Y2 - AC signal detection device for transistor relay - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an AC signal (voltage, current) detection device for a transistor relay.

The first example of a conventional AC signal detection device for a transistor relay is
It is explained in the figure and in the second clause.

Figure 1 shows an AC voltage detection device. PT is a transformer. The primary side of this transformer PT is connected to a bus bar, etc., and the secondary side is made low voltage and connected to the input terminal of a diode bridge rectifier Rf. Connected.

The DC output of the rectifier Rf is input to the voltage comparator circuit CM via the filter circuit FL.

The voltage comparison circuit CM compares the reference voltage and the input voltage, and the comparison output is amplified by the power amplifier circuit Pw and given to the relay iRy.

Fig. 2 shows an alternating current detection device. CT is an auxiliary current transformer. A resistor R is connected in parallel to the secondary side of the auxiliary current transformer CT, and a current is caused to flow through the resistor R. This is a device that detects alternating current by measuring voltage VR.

Note that the same parts as in FIG. 1 are indicated with the same reference numerals.

Since the alternating current detecting device shown in FIG. 2 uses the same circuit as the alternating current voltage detecting device shown in FIG. 1 after converting the current into voltage, the device shown in FIG. 1 will be described below.

In Fig. 1, the output voltage of transformer PT is V o
, if the input voltage to the filter circuit FL is Vi1 and the weir layer voltage of the diode of the rectifier Rf is Vd, then Vi=Vo
It can be expressed by the formula -2Vd.

In this equation, it is known that the weir layer voltage 13 Vd changes with a temperature change of 50°C, so if the output voltage Vo of the transformer PT is made extremely low, the input voltage Vi of the filter circuit PL As is clear from the above equation, Vd varies greatly due to the influence of the weir layer voltage Vd due to temperature changes, making it impossible to obtain a highly accurate AC voltage detection device.

To prevent this, increase the comparison reference voltage of the voltage comparison circuit CM and increase the output voltage Vo of the transformer PT.
It becomes less susceptible to the influence of the weir layer voltage Vd.

However, if the voltage is increased, the power consumption in inputting the operating value increases, and components with high power resistance are required, resulting in an increase in the size of the entire device.

For example, in the case of an AC voltage detection device with an operating value that is very small compared to the rated voltage, there is no need to consider the withstand power of the components near the operating value, but when the rated voltage is applied (e.g. 10 times the rated value (1' direct)) The power is 100 times the operating value power.

Therefore, in order to withstand this power all the time, each component that makes up the transistor relay becomes larger, leading to an increase in the size of this fruiting device, and the power consumption also increases. The benefits of this will be lost.

Particularly, in the case of the alternating current detection device shown in FIG. 2 (in addition, the following drawbacks occur).

For example, in the case of a ground fault overcurrent relay window, when a high sensitivity of 0.25A operation is required for a rated current of 5A, the rated current is 20 times the operating value, but it can withstand up to 200A as an overcurrent withstand. There must be.

In this case, it must withstand an overcurrent that is 800 times the operating value, so when converted to electric power, it is 6400
It becomes 00 times.

In reality, the current transformer CT will be saturated, so the value will not be as large as above, but in any case, in order to withstand extremely large amounts of power, the components of the current-to-voltage converter must be made larger. , and the circuit configuration becomes complicated, reducing the advantages of transistor relays in terms of economy and space.

This invention was made in view of the above circumstances, and aims to provide an AC signal detection device for a transistor relay that has good temperature characteristics, consumes low power, and can be made compact.

An embodiment of this invention will be described below with reference to the drawings.

FIG. 3 shows an AC voltage detection device. In FIG. 3, 1 is a transformer, the primary side of this transformer 1 is connected to a bus bar, etc., and the secondary side has a center tap 2, This tap 2 is connected to the common zero bus.

Ends 3 and 4 of the secondary winding of the transformer 1 are connected to resistors 5,
6 to one end of semiconductor switches 7 and 8 each having a high input impedance with a control terminal (for example, a MOS type bilateral switch).

9 and 10 are waveform shaping circuits;
is used to shape a sine wave into a rectangular wave.

The outputs of both shaping circuits 9 and 10 are connected to the semiconductor switches 7 and 8.
is applied to the control terminal of

1L12 is a varistor, and the varistors 11 and 12 are for preventing overvoltage from being applied to the switch 7.8 when the semiconductor switch 7.8 is off.

13 is an integrating circuit, 14 is a voltage comparison circuit, 15 is a power amplifier circuit, and 16 is an output relay.

Next, the operation on the flow side described above will be described.

When the voltage shown in FIG. 4A is applied to the primary side of the transformer 10, positive and negative voltages appear between the ends 3 and 4 of the secondary side and the center tap 2.

The positive half-wave voltage between the end portion 3 and the center tap 2 is waveform-shaped by a waveform-shaping circuit 9 (shown at the beginning of FIG. 4).
, the waveform-shaped output voltage causes the semiconductor switch 7 to
is turned on.

Therefore, the current 11 (fourth
(shown in FIG. 2) flows to the integrating circuit 13 while being restricted by the resistor 5.

On the other hand, since there is a negative half-wave voltage between the end portion 4 and the center tap 2, the semiconductor switch 8 is in an off state and the current 12 does not flow.

However, when it becomes a positive half-wave voltage, the voltage shown in FIG. 4C is sent to the output of the waveform shaping circuit 10, and the semiconductor switch 8 is turned on by this output voltage.

As a result of this turning on, a current 12 (shown in FIG. 4E) flows through the integrating circuit 13.

Here, if we make the resistances j' of resistors 9.10 and 10 equal, we get
A composite current i (shown in FIG. 4) of the currents j1ti2 becomes a direct current, and this current i is integrated by an integrating circuit 13 over one cycle.

This integrated value is compared with a reference voltage value of the voltage comparison circuit 14, and when the integrated value is equal to or higher than a predetermined value, a comparison output is supplied to the power amplifier circuit 15.

The power amplification circuit 15 amplifies the comparison output to a value at which the output relay 16 can operate.

With the above configuration, compared to the conventional device, it is not affected by the weir layer voltage of the diode, and in the conventional device, one end of the DC output end of the rectifier is connected to the common zero bus for voltage comparison. Because of the necessity, there was a drawback that only one positive or negative DC output could be taken out.

In other words, the transformer output and the rectifier output have a one-to-one correspondence, but the above-mentioned problems are solved in this practical example of the invention.

For example, it is possible to extract any number of rectified outputs of either positive or negative polarity from a single transformer, making it economical for models that require complex relays with multiple functions, such as transistor relays. It has a great effect on target and space.

FIG. 5 1d shows an embodiment of U of this invention, which is applied to an alternating current detection device, especially an overcurrent relay.

Note that the same "subsections" as in FIG. 3 will be described with the same reference numerals.

17 is a current transformer, and resistors 18 and 19 connected in series are connected to the secondary winding of this transformer 17.
The secondary current of the transformer 17 is passed through the transformer 19 to generate a voltage across it.

Further, both ends of the secondary winding of the transformer 17 are connected to resistors 5,
6 to one end of a high input impedance semiconductor switch 7.8 with a control terminal.

20 is a waveform shaping circuit that shapes the voltage generated by the resistors 18 and 19; the output of this circuit 20 is applied to the gate of the semiconductor switch 7 and via the inverting amplifier 21 to the gate of the semiconductor switch 8. .

In this embodiment, if the resistance values of resistors 18 and 19 are equal, the voltage between both resistors 18 and 19 will be the same as the secondary side voltage of the transformer shown in FIG. As shown, a current i flows through the integrating circuit 13.

An overcurrent relay is obtained by integrating the current i in the integrating circuit 13, comparing this integrated value with a reference voltage as in the previous embodiment, and activating the output relay when the integrated value is equal to or higher than a predetermined value.

As described above, according to this invention, the semiconductor switches are turned on alternately by the output of the waveform shaping circuit, and the output of the transformer is passed through the resistor and the semiconductor switch to operate the integrating circuit. Since the resistance change due to temperature during the period when the switch is on can be ignored compared to the resistance value between the transformer and the switch, there is no factor that causes the crystallinity to change as in the conventional case.

Therefore, the comparison voltage can be lowered, AC signals of small input can be reliably produced, and power consumption can be reduced and the power resistance of the components can be reduced.

It also has great effects both economically and in terms of space.

The latter effect is particularly significant in relays with a large dynamic range, such as ground fault overcurrent relays.

[Brief explanation of the drawing]

1 and 2 are circuit configuration diagrams showing a conventional example, FIG. 3 is a circuit configuration diagram showing an embodiment of this invention, and FIG. 4 is a circuit configuration diagram showing a conventional example.
FIG. 5 is a waveform diagram for explaining the operation of the diagram, and FIG. 5 is a circuit configuration diagram showing another embodiment of this invention. 1... Transformer, 5, 6... Resistor, 7, 8... High input impedance semiconductor switch with control terminal, 9, 10, 20... Waveform shaping circuit, 13... Integrating circuit. 14... Voltage comparison circuit, 15... Power amplifier circuit, 17... Transformation>, S, 18, 19... Resistor,
21...Inverting amplifier.

Claims (1)

[Scope of utility model registration request] A device that rectifies AC input from a transformer and drives a transistor relay when the rectified value exceeds a certain value, with terminals provided at both ends of the output side of the transformer, and one end connected to each of these terminals. a pair of series circuits consisting of a semiconductor switch with a predetermined resistance and a high input impedance control terminal; a waveform shaping circuit for shaping the output of the transformer and alternately turning on each of the semiconductor switches with the shaped output; , an integrating circuit to which the other ends of the pair of series circuits are connected, inputting and integrating signals during the on-period of the semiconductor switch, and a voltage comparison circuit comparing and detecting the integrated output of the integrating circuit with a reference voltage. An alternating current signal ejection device for a transistor relay, characterized by comprising: