JPH05196629A - Revolution speed detecting method - Google Patents

Abstract

PURPOSE:To enable an accurate detection of revolutional speed without using a pulse pick-up. CONSTITUTION:A phase voltage of a generator is detected, and its instantaneous value is sampled, for example, at electrical angle of 30 deg.. The time t02' from the first zero-cross point of a voltage waveform at the n-th period to the first sampling time t1, the time t24-t1 from the time t1 to the final sampling time t24 of the voltage waveform at the (n+1)-th period, and the time t241 from the time t24 to the first zero-cross point of the (n+2)-th voltage waveform are added so as to determine the time 2T for two periods. Accordingly, its revolution speed (=1/T) is determined from 2T.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detecting the number of revolutions of a controlled electric device for which frequency control is performed.

[0002]

2. Description of the Related Art Conventionally, when detecting the number of revolutions of a generator,
The generator is equipped with a tachogenerator, or a pulse detection gear is installed to detect the number of revolutions and used for frequency control.

[0003]

In recent years, digitization of control has been implemented, and in order to deal with this, there is no problem if it is a method of detecting the number of revolutions from a pulse pickup. However, the generator main body is old, and there is a problem that it is difficult to attach the pulse pickup when the rotation is detected by a tachogenerator or the like. Therefore, a method for detecting the number of rotations without a pulse pickup is needed.

The present invention has been made in view of the above points, and it is an object of the present invention to provide a rotation speed detecting method capable of accurately detecting the rotation speed without using a pulse pickup.

[0005]

SUMMARY OF THE INVENTION The present invention is a method for detecting the number of rotations of an electric device to be controlled, which detects the instantaneous value of the phase voltage of the electric device to be controlled at a predetermined sampling time. Based on the value, the first time from the first zero-cross point of the voltage waveform of the nth cycle to the first sampling time t ₁ and the time t ₁ to n + 1
The last sampling time t of the voltage waveform of the th cycle
The second time to _END and the third time from the time t _END to the first zero-cross point of the n + 2th voltage waveform are obtained, and two cycles of the phase voltage waveform of the controlled electric device are calculated. Then, the number of rotations is obtained based on the calculation result.

[0006]

The phase voltage waveform of the generator to be controlled is shown, for example, in FIG. Since the sampling time in FIG. 1 is an electrical angle of 30 °, the number of samplings for one cycle is 360 ° / 30 ° = 12.

The first time is calculated as follows from the instantaneous values v ₀ and v ₁ (FIG. 1B) of the sampling times sandwiching the first zero-cross point of the voltage waveform of the nth cycle and the sampling cycle. To do. That is, the first time = sampling period × {v ₁ / (| v ₀ | + v
₁ )} The second time is the first sampling time t
_{From 1} and the last sampling time t ₂₄ (FIG. 1C) of the voltage waveform of the (n + 1) th cycle, the calculation is performed as follows. That is, the second time = sampling cycle × (time t ₂₄ −time t ₁ ) In the third time, the instantaneous value v _{24 of} the sampling time sandwiching the first zero-cross point of the voltage waveform of n + second cycle,
The calculation is performed as follows from v ₂₅ (FIG. 1C) and the sampling period. That is, the third time = sampling period × {| v ₂₄ | / (| v ₂₄
| + V ₂₅ )} Summing the first time, the second time, and the third time, the time 2T for two cycles is obtained. Therefore, the required rotation speed (frequency f) is obtained by f = 1 / T.

As described above, the rotation speed can be obtained only by inputting the detected value of the phase voltage by means of a transformer for instruments or the like without attaching the pulse pickup. Further, since the number of rotations is calculated by calculating two cycles of the voltage waveform, the measurement error is significantly reduced.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. According to the present invention, the instantaneous value of the voltage waveform of the device to be controlled is detected and taken in at a predetermined sampling time, the zero-cross point of the waveform is calculated from this instantaneous value, and the frequency is calculated by back-calculating the zero-cross point.

[0010] FIG. 1 (A) shows the phase voltage waveform of the generator detected by the potential transformer or the like, the sampling time is the electrical angle 30 °, the rated frequency is 50H _Z. FIG. 1 (B) is an enlarged view of the sampling times t ₀ and t ₁ in FIG. 1 (A), and FIG. 1 (C) is shown in FIG.
This is an enlarged view of the sampling times t ₂₄ and t ₂₅ in (A).

In FIG. 1, the sampling period, that is, time t ₁ -time t ₀ (= time t ₀₁ ′ + time t ₀₂ ′) is t ₁
-T ₀ = t ₀₁ ′ + t ₀₂ ′ = (1/50) × (1/12)
= 1/600 (seconds). Here, time 2T for two cycles
Can be obtained by calculating the equation 2T = t ₀₂ ′ + (t ₂₄ −t ₁ ) + t ₂₄₁ ′ (1). In the above equation (1), t ₀₂ ′ is t ₀₂ ′ = (1/600) × {v ₁ / (| v ₀ |
+ V _1)} In sought, t ₂₄ -t ₁ is t ₂₄ -t ₁ = ₍₁ /
600) × (24-1), t ₂₄₁ ′ is t ₂₄₁ ′
= (1/600) × {| v ₂₄ | / (| v ₂₄ | + v ₂₅ )}
Required by. Therefore, from equation (1) above,

[0012]

[Equation 1]

Is required. Therefore, the rotation speed (frequency f) of the generator can be obtained by f = 1 / T (H _Z ) ... (3)

In order to carry out the method of the present invention, for example, a system configuration as shown in FIG. 2 is used. In FIG.
1 is a CPU, 2 is RAM, 3 is ROM, 4 is a bus management unit, 5 is an analog input unit, 6 is a digital input unit, 7 is an analog output unit, and 8 is a digital output unit. The phase voltage of the generator AG is detected by the transformer PT, the instantaneous voltage value is input to the analog input unit 5, and the (1), (2),
The formula (3) is calculated.

[0015]

As described above, according to the present invention, the instantaneous value of the phase voltage of the controlled electric device is detected at a predetermined sampling time, and the phase voltage waveform of the controlled electric device is detected based on the detected value. Since two cycles are calculated and the rotation speed is obtained based on the calculation result, the following excellent effects can be obtained. (1) The rotation speed can be easily detected without attaching a pulse pickup. (2) Since the zero cross of two cycles is used instead of one cycle of the original shape, the measurement error is halved and the rotation speed can be detected with high accuracy.

[Brief description of drawings]

FIG. 1 shows an embodiment of the present invention, where (A) is a voltage waveform diagram of a generator, (B) is an enlarged voltage waveform diagram of a main portion of (A), and (C) is a diagram of (A). The voltage waveform diagram which expanded the part.

FIG. 2 is a block diagram showing a system configuration for executing the rotation speed detection method of the present invention.

[Explanation of symbols]

1 ... CPU, 2 ... RAM, 3 ... ROM, 4 ... Bus management unit, 5 ... Analog input unit, 6 ... Digital input unit, 7 ...
Analog output section, 8 ... Digital output section, AG ... Generator, PT ... Transformer.

Claims (1)

[Claims] 1. A rotation speed detection method for detecting the rotation speed of a controlled electric device, wherein an instantaneous value of a phase voltage of the controlled electric device is detected at a predetermined sampling time, and the n-th value is detected based on the detected value. The first time from the first zero-cross point of the period voltage waveform to the first sampling time t ₁ and the second time from the time t ₁ to the last sampling time t _END of the n + 1th period voltage waveform. And the third time from the time t _END to the first zero-cross point of the n + 2th voltage waveform are calculated, and two cycles of the phase voltage waveform of the electric device to be controlled are calculated. A method for detecting the number of revolutions, characterized in that the number of revolutions is obtained based on.