JPS644130B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a voltage or ammeter with an instantaneous indicator.

Instantaneous type voltage or ammeters with indicator needles are mainly used to monitor the amount of electricity that changes instantaneously when a system failure occurs at power plants, substations, etc., such as fault current and voltage. The value of the fault current and voltage that occurs can be checked using the indicator. This type of meter needs to have a response time as fast as 0.1 because the change in the amount of electricity to be measured is instantaneous. That is, a fast response speed is required, with an instruction time of about 0.1 seconds until 100% of the measured value is indicated.
On the other hand, in general, for meters with a pointer, if the frictional rotational force of the pointer is not set to about 150mg-cm, the pointer will move due to vibrations, etc., so the meter's rotational force should be set to about 15g-cm to be within the standard tolerance. There is. In addition, in the case of the instantaneous type, the main hand operates at high speed, causing the center hand to fly due to damping (excessive movement), so it is necessary to increase the braking force. However, increasing the braking force slows down the movement, so it becomes necessary to increase the rotational force of the meter. As a compromise between these contradictory characteristics, in the conventional instantaneous voltage or ammeter with a needle, the rotational force of the meter is set to a value larger than that of a general meter, which is about 60 g-cm. Therefore, the permanent magnet used in the meter had to be very large.
Conventionally, even with this, it has not been easy to fully adjust the conflicting characteristics as described above, and adjustment of this type of meter has required skill. In other words, if the rotational force of the meter is increased relative to the braking force, the indicating operation will become faster, but the indicator will break off due to inertia and the correct indication will not be given. On the other hand, if the rotational force of the meter is too small compared to the braking force,
It becomes impossible to obtain a response time as fast as 0.1 seconds. Therefore, in the past, some companies took compromise measures such as being satisfied if an indication of about 95% of the measured value could be obtained in 0.1 seconds.

SUMMARY OF THE INVENTION In view of the prior art as described above, an object of the present invention is to provide a voltage or ammeter with an instantaneous indicator needle that is small in size, does not require skill for adjustment, and is capable of giving accurate instructions.

According to the present invention, the rotational force of the meter is suppressed to a small value, the braking force is reduced in order to increase the response speed, and the problem of excessive needle movement is solved by providing an automatic adjustment circuit in the input circuit to the meter to input the measured input. The above object is achieved by configuring the instantaneous voltmeter or ammeter so that the rise in volume is prevented by automatic control.

Next, the present invention will be described in more detail with reference to embodiments of the present invention based on the accompanying drawings.

FIG. 1 schematically shows the configuration of a voltage or ammeter with an instantaneous indicator as an embodiment of the present invention. In this Figure 1, M is a movable ring type meter with a needle, and the rotational force of this meter M is 20
The value is considered to be small, on the order of g-cm, and therefore, the permanent magnets used for this purpose are extremely small. Normally, a voltage or current waveform, which is the quantity to be measured, is directly applied to this type of meter M via an instrument current transformer or transformer 1 and a rectifier 2. , a nonlinear resistance circuit 10 and a capacitor 20 are connected to the input circuit of the meter M.
An automatic adjustment circuit is provided. This non-linear resistance circuit 10 may have any configuration as long as it exhibits a small resistance value when the input voltage applied thereto is large and a large resistance value when the input voltage is small.
It is composed of resistors 11 and 12 and a constant voltage diode 18. Capacitor 3 is added simply for ripple removal.

Generally, the amount of overshoot of the meter's pointer needle is determined by the operating torque of the meter's movable part (which changes depending on the current in the movable ring), the moment of inertia, and friction, but in the case of this type of meter, friction can be ignored. Since the moment of inertia is determined by the motor structure, it changes only by the current flowing through the movable ring. Therefore, the greater the amplitude of the instantaneously generated voltage or current waveform that is the measured quantity, that is, the greater the current flowing through the movable wire of the meter, the greater the amount of overshoot of the meter's main needle and indicator needle. You'll probably get used to it. However, according to the present invention, this problem is eliminated by the action of the automatic adjustment circuit consisting of the nonlinear resistance circuit 10 and the capacitor 20. This point will be explained in more detail with reference to FIG.

In the circuit shown in FIG. 1, when the rising edge of the voltage waveform to be measured is large, the nonlinear resistance circuit 10 exhibits a smaller resistance value, so that the nonlinear resistance circuit 10 exhibits a smaller resistance value. The rise of the input current can be suppressed. The degree to which the rise of this input current is suppressed increases as the rise of the voltage waveform to be measured becomes larger. Therefore, by appropriately selecting various parameters of the nonlinear resistance circuit 10 and the capacitor 20, the input current to the movable wire of the meter M can be adjusted as shown in FIG. can be made as shown by the solid line curve A, so that the meter M
The movement of the main hand can be made as shown by a curve B shown in dotted lines in FIG. 2, and the movement of the positioning hand can be made as shown in a curve C shown in dashed lines in FIG.

As described above, according to the present invention, the input current waveform to the meter is automatically adjusted as shown in curve A in FIG. 2, regardless of the amount of instantaneous change in the measured quantity. Even if the braking force of the meter is small, the problem of overshooting the needle does not occur at all, and accurate needle setting instructions can always be given. Moreover, since the turning force of the meter is small, the permanent magnet used can also be small, and the entire meter can be made compact. On top of that,
The above-mentioned automatic adjustment circuit only needs to be appropriately designed in advance, and there is no need for the conventional work that requires skill, such as mechanically adjusting the rotational force and braking force of the meter to find a compromise.

[Brief explanation of drawings]

FIG. 1 of the accompanying drawings is a schematic circuit diagram showing one embodiment of the present invention, and FIG. 2 is a diagram showing curves for explaining the operation of the embodiment of FIG. 1. 1... Instrument current transformer or transformer, 2... Rectifier, 10... Non-linear resistance circuit, 20... Capacitor, M... Meter.

Claims (1)

[Claims] 1. An instantaneous voltage or ammeter with an instantaneous indicator, characterized by comprising a meter with an instantaneous indicator, and an automatic adjustment circuit consisting of a series circuit of a nonlinear resistance circuit and a capacitor connected to the input side of the meter.