JP3297243B2 - Speed measurement circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rotational speed measuring circuit usable as one of turbine monitoring instruments, and more particularly to a rotational speed capable of detecting a low rotational speed of a turbine generator and transmitting a contact output. It relates to a measurement circuit.

[0002]

2. Description of the Related Art A general turbine generator generates power by rotating a turbine at high speed with steam and rotating a generator connected to the turbine. When raising the turbine to the rated speed, first perform a turning operation to take a temporary bend (eccentricity) of the turbine axle by performing a smoothing operation in which the turbine is rotated at a low speed, and make the eccentricity of the turbine axle sufficiently small. While monitoring the vibration of each bearing stand, the rotation speed is increased to the rated rotation speed. Also,
Even when the turbine is stopped, when a predetermined low rotation speed is reached, a turning operation is performed by connecting a turning gear to prevent the eccentric amount from being generated on the turbine axle while continuing rotation at a low rotation speed. .

[0003] In connection of the turning gear, the rotation speed of the turbine axle is constantly detected, and when the turbine speed becomes low, the fact is notified to the outside and the connection timing is given. Therefore, it is necessary to accurately measure the number of rotations of the turbine axle at low rotation.

FIG. 3 shows a configuration example of a conventional rotation speed measuring circuit. The rotation number measuring circuit 10 converts a signal from the rotation detector 11 into a capacitor 12A and a resistor 12B.
The DC component is cut off by passing the signal through the circuit, and the signal from which the DC component has been cut is subjected to impedance conversion by the buffer 12C and applied to the buffer 12C as a rotation speed signal. The comparator 12D outputs a square wave proportional to the rotation speed signal. This square wave has a frequency characteristic according to the number of rotations, and is called a rotation frequency signal. This rotation frequency signal is converted by an F / V conversion circuit 12E into a voltage signal proportional to the rotation frequency signal. This voltage is converted into a DC voltage with a small ripple voltage by the smoothing circuit 12F, and the ripple voltage is further minimized by the smoothing circuit 12G. The rotation speed voltage signal smoothed so as to minimize the ripple voltage is input to a comparator 12H and compared with a predetermined threshold voltage. When the rotation speed voltage signal becomes lower than the threshold voltage, the relay 1
Operate 2J to send contact output to outside. Reference numeral 12H is a setting circuit for setting a threshold voltage for the comparator 12H.

[0005]

However, the above-described rotation speed measuring circuit has no problem when the rotation speed is high because the ripple voltage of the rotation speed signal is small. However, when the rotation speed is low (low rotation), the rotation speed signal is low. Since the ripple voltage superimposed on the comparator 12H becomes large, there is a disadvantage that the comparator 12H malfunctions due to the fluctuation of the ripple voltage near the threshold voltage of the comparator 12H and the relay 12J causes chattering.

In order to reduce the ripple voltage in the low rotational speed range, the time constant of the smoothing circuits 12F and 12G may be increased. However, the response time becomes very slow due to the increase of the time constant, and the rotational speed is measured. Causes inconvenience.

The present invention has been made in view of the above circumstances, and has as its object to provide a highly reliable rotation speed measuring circuit which does not malfunction even in a low rotation speed range where the rotation speed is low.

[0008]

In order to achieve the above object, the present invention takes the following measures. According to the present invention, a rotation speed signal output from a rotation detector is taken in, a rotation speed is determined, and when a predetermined rotation speed is reached, a relay drive circuit is operated to output a relay contact output to the outside. in the rotation speed measuring circuit for transmitting a or said speed signal
The count value of the counter circuit is preset to an initial setting value based on a pulse signal output through the one-shot circuit, and the count value of the counter circuit is down-counted in synchronization with a clock signal. When 0 reaches 0 , the relay drive circuit is operated to transmit a relay contact output , and
After closing, the second output from the one-shot circuit
Condition between the pulse signal and the output of the counter circuit
Is not established for the first time.
I set the road .

[0009]

The present invention has the following effects by taking the above measures. According to the first aspect of the present invention, the count value of the counter circuit is preset to an initial set value by a pulse signal having a cycle proportional to the rotation speed as the rotation speed signal, and the count value of the counter circuit is synchronized with the clock signal. Then, it is counted down from the initial set value. When the down count number in the counter circuit reaches 0 , the relay drive circuit operates and a relay contact output is transmitted. Therefore, there is no need for the comparator to make a relay judgment in comparison with the reference voltage, so there is no need to worry about malfunction of the comparator due to fluctuations in the ripple voltage. Can be detected with a high degree of accuracy up to a low rotation speed without lowering the rotation speed. After turning on the power,
The second pulse signal output from the
AND condition with the output of the data circuit becomes unsatisfied for the first time
The relay drive circuit is set based on the above. Follow
At least after setting the relay drive circuit
Operation will be performed.

[0010]

Embodiments of the present invention will be described below. FIG. 1 shows a configuration of a rotation speed measuring circuit according to one embodiment of the present invention. In the rotation speed measuring circuit 20 of the present embodiment, the inverting input terminal of the comparator 21 is connected to a terminal at which the output of the rotation detector 11 appears via a resistor, and the output terminal of the comparator 21 is connected via a diode 22 and a resistor 23. Connected to earth. The output terminal of the comparator 21 and the anode of the diode 22 are connected to a non-inverting input terminal via a resistor and to the ground. A first one-shot circuit 24 is connected between the diode 22 and the resistor 23 and further connected to the first one-shot circuit 24.
The second one-shot circuit 25 and the gate circuit 2
6 are connected in series. The gate circuit 26 is connected to the reset terminal of the counter circuit 27, and the switch circuit 28 is connected to the initial value setting terminal of the counter circuit 27. The count value output terminal of the counter circuit 27 is connected to a reset terminal of an RS flip-flop circuit including an OR gate 29 and a latch gate circuit 31. Note that the output of the gate circuit 26 is input to the set terminal of the RS flip-flop circuit. Also, the counter circuit 27
Are supplied with a clock signal from the clock generation circuit 30. The output of the latch gate circuit 31 is RS
The output of the flip-flop circuit is input to the first AND gate 32. The output of the delay circuit 33 is input to the first AND gate 32 via the changeover switch 34. Also, the outputs of the first one-shot circuit 24 and the latch gate circuit 31 are input to a second AND gate 35,
The AND output is supplied to the third AND via an inverter 36.
Input to gate 37. Third AND gate 37
Inputs the output of the delay circuit 33 via the changeover switch 34.

A first AND gate 32 and a third AND gate
Each AND output of the gate 37 is input to a relay drive circuit 38. The relay drive circuit 38 is composed of an RS flip-flop circuit, and has a set terminal connected to the output of the first AND gate 32 and a reset terminal connected to the output of the third AND gate 37. This relay drive circuit 3
The Q output of 8 controls the gate terminal of the transistor switch 39 to operate the relay 40 provided between the collector of the transistor switch 39 and the common. Relay 4
In the case of 0, photodiodes 41 and 42 are arranged in series in the forward direction between the common and the collector of the transistor switch 39, and photo FETs 43 and 44 are provided corresponding to both photodiodes 41 and 42.

Next, the operation of the embodiment constructed as described above will be described with reference to the time chart of FIG. The rotation detector 11 detects the rotation of the turbine axle and sends a rotation speed current signal corresponding to the rotation speed to the comparator 21 of the rotation speed measurement circuit 20. This signal is converted by the comparator 21 into a square wave (INPUT), and only the positive output (0 V to + V) is taken out by the diode 22 and the resistor 23 and input to the first one-shot circuit 24 to be fixed at the falling edge of the square wave. Shape into a square wave (PIN) of width. The signal whose waveform has been shaped by the first one-shot circuit 24 is converted into a signal (APE) by which the counter circuit 27 can operate by the second one-shot circuit 25 and the gate circuit 26, and the converted signal is sent to the counter circuit 27 as a preset signal. give.

The counter circuit 27 includes a clock generation circuit 3
It counts down in synchronization with the clock signal input from 0, and is preset to the count value (set value) set by the switch circuit 28 each time a preset signal is input from the gate circuit 26.

As shown in FIG. 2, since the period of the preset signal is shortened in proportion to the increase of the rotation speed, the switch circuit 28 sets the period of the preset signal corresponding to the low rotation speed to be detected as a set value from the switch circuit 28. Set in the circuit 27. If such a count value is set as a set value in the counter circuit 27, the count value of the counter circuit 27 becomes 0 because the rotation speed becomes the low rotation speed to be detected, and R
A pulse signal (reset signal) is sent to the reset terminal of the S flip-flop circuit (27, 31).

Here, the RS flip-flop circuit (2)
7, 31), the output (Tw) rises with the signal (APE) first output from the gate circuit 26, and the high level is maintained until the count value of the counter circuit 27 becomes 0 and the reset signal is input. At the time when the reset signal is input.

On the other hand, the changeover switch 34 is switched to the terminal b when detecting arrival in the low speed range, and the first A
A predetermined potential is applied to the ND gate 32. Therefore, the output of the first AND gate 32 is at the high level until the count value of the counter circuit 27 reaches 0, and the same as when the output (Tw) of the latch gate circuit 31 changes to the low level. Changes to a low level. As a result, an alarm signal is given from the relay drive circuit 38 to the transistor switch 39, and the transistor switch 39
Operates, and the relay 40 operates to transmit a relay contact output to the outside. That is, the transistor switch 3
The gate terminal 9 turns on, the photodiodes 41 and 42 of the relay 40 emit light, and the photo FETs 43 and 44 notify the outside that the low rotation speed has been reached.

For example, if the count value of the counter circuit 27 is set to a count value corresponding to 0.5 rpm, the count value of the counter circuit 27 is always preset when a rotation speed signal of 0.5 rpm or more is input. The state continues, and the output of the counter circuit 27 is not transmitted. Therefore, since the transistor switch 39 does not operate, the relay 40 does not operate, and no contact output is transmitted to the outside. When the number of revolutions becomes 0.5 rpm or more, the count value of the counter circuit 27 is counted down to 0 and becomes 1
Pulse output. This one pulse is applied to the latch gate circuit 3
Since it is latched at 1 and input to the relay drive circuit 38, the transistor switch 39 operates, the relay 40 operates, and a relay contact output is transmitted to the outside.

The switch 34 has been previously switched to the terminal a when the power is turned on. Therefore, after the power is turned on, a predetermined potential is applied to the third AND circuit 37 via the delay circuit 33 with a delay of a predetermined time. On the other hand, the third AND
When the second pulse signal (PIN) is input from the one-shot circuit 24 to the second AND gate 35, the gate 37 does not satisfy the AND condition.
Set 8 At least, after the relay drive circuit 38 is set, the changeover switch 34 is switched to the terminal b to perform the above operation.

As described above, according to the present embodiment, a count value corresponding to the number of revolutions to be detected is set in the counter circuit 27, and this count value is preset by a signal (APE) having a period proportional to the number of revolutions. When the counter circuit 27 counts up the set value, a contact output is transmitted to the outside. Therefore, all the circuits can be configured in a digital system without providing a smoothing circuit, etc. Up to a number can be detected with high accuracy. Further, by setting the count value of the counter circuit 27 arbitrarily, a contact output can be transmitted to the outside at any rotation speed from a low rotation speed to a high rotation speed. The present invention is not limited to the above embodiments, and various modifications can be made without departing from the spirit of the present invention.

[0020]

As described in detail above, according to the present invention, even in a low rotation speed range where the rotation speed is low, a desired rotation speed can be detected without any malfunction and a contact output can be transmitted to the outside, thereby improving reliability and responsiveness. It is possible to provide an excellent rotation speed measurement circuit.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a rotation speed measurement circuit according to an embodiment of the present invention.

FIG. 2 is a time chart of a rotation speed measuring circuit according to one embodiment.

FIG. 3 is a configuration diagram of a conventional rotation speed measurement circuit.

[Explanation of symbols]

11: rotation detector, 20: rotation speed measurement circuit, 21: comparator, 27: counter circuit, 28: switch circuit,
29 ... OR gate, 31 ... Latch gate circuit, 32 ... First AND gate, 35 ... Second AND gate, 37 ...
Third AND gate, 38 relay drive circuit, 39 transistor switch, 40 relay.

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) G01P 3/42-3/489 H02P 9/04 H02P 5/00

Claims (1)

(57) [Claims] 1. A rotation speed at which a rotation speed signal output from a rotation detector is taken in, a rotation speed is determined, and when a predetermined rotation speed is reached, a relay drive circuit is operated to transmit a relay contact output to the outside. In the measurement circuit, the rotation speed signal is output through a one-shot circuit.
That the count value of the counter circuit based on a pulse signal with preset to an initial setting value, counts down in synchronism with the clock signal count value of said counter circuit, the relay if the number of down count reaches 0 Activate the drive circuit to transmit the relay contact output , and after turning on the power,
The second pulse signal output from the
Based on the fact that the AND condition with the output is not satisfied for the first time
A rotational speed measuring circuit for setting the relay drive circuit.