JPH0431766A - Detecting circuit for rotational speed - Google Patents

Abstract

PURPOSE:To execute highly-precise detection of a rotational speed by a construction wherein a pulse of each phase outputted by a multiphase converter is counted by a counter. CONSTITUTION:Alternating-current signals 3 of three phases are inputted also to an arithmetic circuit, and an output obtained by adding up a signal obtained by attenuating an alternating-current signal of a first phase by an attenuator 7 and an alternating-current signal of a second phase and a signal obtained by attenuating an alternating-current signal of a third phase by the attenuator 7 being taken for one phase afresh respectively, signals of six phases in all are inputted to voltage comparators 8g to 8l respectively. Therefore, the voltage comparators 8g to 8l output signal pulses delayed by 1/3<1/2> and ones advanced by 1/3<1/2> from the aforesaid alternating-current signals of three phases respectively. Then, the phase voltages (or line voltages) of a three-phase alternating current thus obtained are converted into pulses by voltage comparators 8a to 8l respectively and the number of pulses (or time intervals of pulses) within a prescribed time is measured by a counter 9. Thereby an output value 10 being proportional to a rotational speed (or a cycle of rotation) can be determined.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a rotation speed detection circuit that detects the rotation speed of a device under test that is a rotating machine.

[Conventional technology]

FIG. 3 is a block diagram showing a conventional rotational speed detection circuit. In the figure, 1 is a device to be measured which is a rotating machine whose rotational speed is to be measured, and 2 is a device to be measured that is connected to and driven by this device to be measured. An AC synchronous generator, 3 an AC signal generated by the AC synchronous generator 2, 8 a voltage comparator for comparing the AC signals 3 of each phase, and 9 a counter for counting the number of pulses.

Next, the operation will be explained.

First, when the device to be measured M1 rotates, the AC synchronous generator 2 that rotates integrally therewith generates an AC signal 3 for each phase with a frequency proportional to its rotational speed.

The voltage comparator 8 compares the AC signals 3 of each phase and generates a pulse having a phase according to the comparison result. Therefore, the counter 9 outputs an output value 10 proportional to the rotation speed or rotation period of the device to be measured 1, which is a rotating machine, by measuring the number of pulses or the time interval of the pulses within a certain period of time.

[Problem to be solved by the invention]

Since the conventional rotational speed detection circuit is configured as described above, the number of poles of the AC synchronous generator 2 that detects the speed is small, so accurate speed detection cannot be performed. This requires the use of a large AC synchronous generator with a large number of poles, and in some cases requires the use of an expensive pulse generator.

This invention was made to solve the above-mentioned problems, and even if a conventional AC synchronous generator is used, the speed detection accuracy is equivalent to that of an AC synchronous generator with a large number of poles. The purpose is to obtain a rotation speed detection circuit that can obtain the following results.

[Means to solve the problem]

The rotational speed detection circuit according to the present invention includes an AC synchronous generator connected to a rotating device under test and driven vertically, and a multiphase signal generated from each phase signal generated by the AC synchronous generator. The converter includes a multi-phase converter that converts pulses and outputs the converted pulses, and a counter counts the pulses of each phase output by the multi-phase converter.

[Effect]

The polyphase converter in this invention generates more pulses than the number of pulses generated when the AC synchronous generator rotates once.
By using an operational amplifier, a transformer, etc., it is possible to detect the rotational speed of the device under test with high precision.

[Embodiments of the invention]

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

In Figure 1, 1 is a device to be measured which is a rotating machine whose rotational speed is to be measured, 2 is a three-phase AC synchronous generator for speed detection, and an AC signal 3 with a frequency proportional to the rotational speed is sent to each phase. occurs in 4 is an integrating circuit that smoothes the AC signal 3;
5 is an adder circuit that calculates the average value of the three-phase AC signals. 6
1 is an arithmetic circuit, and 7 is an attenuator provided in the arithmetic circuit 6, which together with an adder 11 outputs six phases of alternating current signals.

In this embodiment, this damping ratio is, for example, 0.577 (=1/
f1), 8a to 81 are voltage comparators serving as multiphase converters, which compare the output of each phase and the delayed output supplied via the integration circuit 4, and output pulses for 12 phases. do. 9 is a counter that counts the pulses of each phase.

Next, the operation will be explained.

First, when the device to be measured 1 rotates, the three-phase AC synchronous generator 2 that rotates integrally therewith generates three-phase AC signals 3 for each phase at a frequency that is compared to the rotational speed of the device. First, two phases of these three-phase AC signals 3 are connected to a voltage comparator 8a.
, 8b, and 8c, and a pulse having a phase corresponding to each phase difference is generated.

Further, the AC signals 3 of each three phases are added in an adding circuit 5 to obtain an average value, and this average value and the AC signals 3 of each phase are inputted to voltage comparators 8d, Be, and 8f, and the above-mentioned pulse A pulse with the opposite phase is generated.

Furthermore, the three-phase AC signal 3 is also input to the arithmetic circuit 6, and the output is the sum of the first-phase AC signal attenuated by the attenuator 7, the second-phase AC signal, and the third-phase AC signal. The AC signal and the signal attenuated by the attenuator 7 are newly set as one phase, and a total of six phases are input to each voltage comparator 8g to 81. For this reason, each voltage comparator 8g to 81 receives a signal delayed by 1/f1- with respect to each of the three-phase AC signals and a signal delayed by 1/v'T.
Outputs signal pulses that advance in steps. The counter counts each of these pulses, detects it as a highly accurate rotational speed signal divided into 12 parts of the device under test N1, and outputs it.

Next, a method of converting such a three-phase AC signal into a 12-phase AC signal will be explained with reference to the vector diagram shown in FIG.

Generally, a conversion formula can be used to synthesize an AC signal X with a phase of 0° and an AC signal Y with a phase of 60° to obtain an AC signal 2 with an arbitrary phase θ. Therefore, the phase voltage (or line voltage) of each phase of the obtained three-phase AC is converted into pulses by voltage comparators 8a to 81, and the counter 9 calculates the number of pulses (or time interval of pulses) within a certain period of time. By measuring, it is possible to obtain an output value 1o that is proportional to the rotation speed (or rotation period).

Note that the integration circuit 4 converts the AC signal 3 whose amplitude increases in proportion to the frequency into a constant amplitude and also attenuates noise, but this can be omitted if the subsequent circuit allows it.

In the above embodiment, three-phase alternating current is converted to twelve-phase alternating current, but the resolution may be further improved by further converting to multi-phase alternating current of twelve or more phases.

Further, in the above embodiment, operational amplifiers are used in the voltage comparators 8a to 81 as polyphase converters for converting from 3-phase AC to 12-phase AC. A transformer with multiple windings may also be used.

〔Effect of the invention〕

As described above, according to the present invention, an AC synchronous generator is connected to and driven by a rotating device under test, and a multiphase signal is generated from each phase signal generated by the AC synchronous generator, and this is pulsed. It is equipped with a multi-phase converter that converts and outputs it, and is configured so that the pulses of each phase output by the multi-phase converter are counted by a counter, so it is equivalent to a multi-phase AC synchronous generator with a large number of poles. It is possible to obtain the same speed resolution performance as when using the .

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing a rotational speed detection circuit according to an embodiment of the present invention, Fig. 2 is a vector diagram showing the principle of phase number conversion according to an embodiment of the invention, and Fig. 3 is a conventional rotational speed detection circuit. FIG. 2 is a circuit diagram showing a circuit. 1 is a device to be measured, 2 is an AC synchronous generator, 8a to 81 are voltage comparators, and 9 is a counter 6. In the drawings, the same reference numerals indicate the same or corresponding parts. (2 others) Fig. 2-S F-T- (Fig. 3

Claims (1)

[Claims] An AC synchronous generator connected to and driven by a rotating device to be measured, and a polyphase converter that generates a polyphase signal from each phase signal generated by the AC synchronous generator, converts it into pulses, and outputs it. , and a counter that counts pulses for each phase output by the multiphase converter.