JPH0467425B2 - - Google Patents

Description

[Detailed description of the invention] [Technical field to which the invention pertains] The present invention detects the occurrence of an open phase state in a three-phase electric circuit to which a motor or the like is connected based on the degree of unbalance of line current in the three-phase electric circuit. Open phase detection device,
In particular, the operation delay time from detecting an open phase state to outputting an open phase detection signal is short and stable, and in addition, it is easy to set the standard for the unbalance degree, which is the standard for detecting an open phase. Regarding device configuration.

[Prior art and its problems]

If one phase of a three-phase electric circuit that drives a three-phase motor becomes open-phase due to circuit breakage or poor circuit connection, the line current of the three-phase electric circuit becomes unbalanced, causing an excessive current in the motor windings. flows, resulting in inconveniences such as burnout of the motor. Therefore, in order to prevent such problems from occurring, an open phase detection device is usually installed that detects the current in the three-phase circuit using a current transformer, etc., and outputs an open phase signal when the balanced state of the current becomes abnormal. The main circuit of the motor is configured such that power can be supplied to the motor via a circuit opening/closing device that opens when the open phase signal is input.

FIG. 3 is a block diagram of the conventional open-phase detection device as described above _. The three-phase full-wave rectifier receives the output signals of CT ₂ and CT ₃ , performs three-phase full-wave rectification on these signals, and outputs a rectified signal 1a having a signal waveform as shown by the solid line in FIG. wave rectifier, 3
Reference numeral 4 refers to a peak value detection means that receives the rectified signal 1a and outputs a peak value signal 3a corresponding to the peak value of the signal 1a; 4 receives the rectified signal 1a and outputs an average value signal 4a that corresponds to the average value of the signal 1a; This is an average value detection means to output. 5, the peak value signal 3a is input,
It is determined whether the value of the current in the electric circuit 2 represented by the signal 3a is a value that requires the present phase loss detection device to perform a regular phase loss detection operation such as outputting the phase loss signal. In the current judgment circuit that judges, if the current in the electric line 2 is small, the motor will not burn out even if an open phase state occurs in the electric line, so if the signal 3a is small, the judgment circuit 5 outputs an output signal 5a having the function described below. It is configured as follows.

FIG. 4 When a one-phase missing state occurs in the delta winding of the motor in FIG. 3, the waveforms of the signals 1a, 3a, and 4a become as shown in FIG. 4Z. As can be seen from Figure 4,
In FIG. 3, when an open phase state occurs in the electric circuit 2, the pulsation rate R of the signal 1a, which is expressed as (A-B)/A, where the magnitudes of the signals 3a and 4a are A and B, respectively, is It is usually larger than when the open phase state does not occur in the electric circuit 2. Reference numeral 6 in FIG. 3 is a calculation means that calculates this pulsation rate R and outputs a pulsation rate signal 6a corresponding to the R. This calculation means 6 receives signals 3a and 4a and outputs a
−B is subtracted and the signal 7 corresponds to the result C of the subtraction.
a, and a division means 8 which receives the signals 3a and 7a, performs division by C/A, and outputs the result of the division, that is, a signal 6a corresponding to the pulsation rate R. ing. Both the subtraction means 7 and the division means 8 are configured so that they do not perform arithmetic operations when the signal 5a is input. 9 has a reference pulsation rate R ₀ set, and when the pulsation rate R represented by the input signal 6a and the reference pulsation rate R ₀ are compared and the former value is greater than or equal to the latter value, it becomes H level. The reference pulsation rate _R0 is determined by the output of the signal 9a because the pulsation rate R increases when an open phase state occurs in the electric circuit 2, as described above. The setting is such that the condition is recognized as having occurred. τ is the signal processing time required for outputting the signal 9a from the open-phase determining means 9 after the current flowing through the electric path 2 is detected by the current transformers CT ₁ to CT ₃ . Reference numeral 10 denotes a clock means for inputting a signal 9a and outputting one pulse signal 10a as a time-up signal after time ΔT when the signal 9a becomes H level, and 11 for counting and accumulating the number of pulse signals 10a. When the number reaches the set value N, an open phase signal 11a is used as a count up signal.
This is a counting means that outputs .

Since each part of the open phase detection device shown in FIG. When the clocking means 10 performs a timing operation after the timing has been determined, the occurrence of an open phase state in the electrical circuit 2 is detected by the output signal 10a of the clocking means. signal processing time τ
Since the series of operations consisting of the operations of the above-mentioned parts and the timekeeping operation of the timekeeping means 10 are repeatedly executed, even if the series of operations is repeated N times, the pulsation rate R remains constant. If the state in which R exceeds the reference value _R0 continues, the counting means 11 will output an open phase signal 11a. The circuit opening/closing device described above opens the motor main circuit and stops the motor when the open phase signal 11a is input. The _reason why the device shown in FIG. Depending on the increase in rate R,
Since the electric motor will not burn out, the main circuit of the electric motor will not be disconnected, and the operating time ΔT of the timer 4 mentioned above is a time set based on equation (1). In equation (1), T is
The time required to confirm the continuation of the above-mentioned open phase state in the open phase detection device, in other words, the rated operation delay time of the open phase detection device, and the size of N is appropriately set in consideration of the time accuracy of open phase detection. There is.

△T=T/N... (1) In Fig. 3, the open phase detection device operates as described above, so the open phase state that continues to occur in the electric circuit 2 is expressed by equation (2). Counting means 1 after time T ₀ elapses
This is detected by the phase loss signal 11a output from 1. Therefore, such an open phase detection device has the problem that the detection time is longer than the rated time T by N·τ (T ₀ =N·(τ+△T)=N·τ+T (2)). , and the signal processing time τ
Most of the time constituting is the time t spent on the calculation operation in the calculation means 6, and since (A/B)<A in this calculation method, the value of (A-B), in other words, the pulsation. Minute C multiplied by a certain constant to A
Since it is customary to repeatedly subtract , the calculation time t in the calculation means 6 changes depending on the values of A and B, and as a result, the time τ changes depending on the values of A and B. The detection device shown in the figure also has a problem in that the open phase detection time is not constant. Furthermore, in the detection device shown in Fig. 3, it is assumed that an open phase condition has occurred when the pulsation rate R exceeds the reference value _R0 , but this may be caused by, for example, an unbalanced current that inevitably occurs when starting the reactor of an induction motor. However, the pulsation rate R increases, and it is generally difficult to distinguish between the pulsation rate value in this case and the pulsation rate value at the time of an open phase.
The open phase detection device shown in the figure also has a problem in that it is difficult to set the reference value R ₀ .

[Purpose of the invention]

The present invention solves the problems in the conventional phase-opening detection device as described above, and allows the phase-opening detection time to match the rated operation delay time without being influenced by the peak value or average value of the rectified signal 1a. It is an object of the present invention to provide an open phase detection device that does not change and allows easy setting of a pulsation rate reference value that serves as a reference for open phase detection.

[Key points of the invention]

In order to achieve the above object, the present invention includes three current detection means for detecting each line current in a three-phase electric circuit; each output signal of these detection means is inputted, and a three-phase full-wave rectified rectified signal is output. three-phase full-wave rectification means; peak value detection means for outputting a peak value signal according to the peak value of the rectified signal; average value detection means for outputting an average value signal according to the average value of the rectified signal;
A first determining means that compares the value of the signal to be determined, which is one of the peak value signal and the average value signal, with a built-in first set current value, and outputs a first determination signal when the former is greater than or equal to the latter. A second circuit that compares the value of the signal to be determined with a built-in second set current value, and outputs a 21st determination signal if the former is less than the latter, and outputs a 22nd determination signal if the former is greater than or equal to the latter. determining means; calculating means for performing calculations using the peak value signal and the average value signal and outputting a pulsation rate signal according to the pulsation rate of the rectified signal; and determining whether a reset signal is input or a time-up signal is output. a timekeeping means that is then reset to the initial state and stops the timekeeping operation, starts the timekeeping operation when the first determination signal is input, and outputs the time-up signal after a set time elapses;
A first reference value and a second reference value are provided, and when the 21st determination signal is input, the value of the pulsation rate signal and the first
When the pulsation rate signal is compared with the second reference value and the former is less than the latter, the reset signal is output, and when the 22nd judgment signal is input, the value of the pulsation rate signal is compared with the second reference value and the former is lower than the latter. and a third determining means for outputting the reset signal if the time-up signal is not satisfied, the phase-opening detection device is configured to detect the occurrence of a phase-opening in the three-phase electric circuit based on the time-up signal.
With this configuration, the calculation time of the pulsation rate in the calculation means is prevented from affecting the open phase detection time, and the open phase detection time is approximately equal to the set time in the time measurement means. Accordingly, it is possible to obtain an open phase detection device that does not change depending on the peak value or average value of the rectified signal. In addition, when the peak value or average value of the rectified signal is small, the pulsation rate reference value as the criterion for open phase determination is set to the first reference value, which is a small value. When the peak value or the average value becomes large, the pulsation rate reference value is set to a second reference value that is larger than the first reference value, so that the open phase detection device does not malfunction when starting the electric motor, etc. In this manner, it is possible to obtain an open phase detection device in which the pulsation rate reference value can be easily set.

[Embodiments of the invention]

FIG. 1 is a block diagram of an embodiment of the present invention, and the main difference from FIG. 3 is that first to third determination means 12 to 14 are provided. In this case, the first determination means 12 receives the peak value signal 3a and compares the magnitude A of the input signal with a built-in first set current value _I1 , and if A≧ _I1 , the first determination means 12 outputs a first determination signal 3a.
The second determining means 13 is configured to output a.
In this case, the peak value signal 3a is input, and the magnitude A of the input signal is compared with the built-in second set current value _I2 to find that A<
If it is I ₂ , the 21st judgment signal 13a is output, and if A
It is configured to output the 22nd determination signal 13b if ≧I ² . In this case, it is set so that I ₁ <I ₂ . Furthermore, the third determination means 1
4, the means 14 is provided with a first reference value R ₁ and a second reference value R ₂ larger than this R 1 , and when the 21st judgment signal ^13a is input, the judgment means 1
The value R of the output signal 6a of _the arithmetic means inputted to 4 is compared with the first reference value R1, and if R< _R1 , the reset signal 14a is output, and the 22nd judgment signal 13 is
b is input, the value R of the signal 6a and the second
It is configured to compare it with a reference value _R2 and output a reset signal 14a if R< _R2 . In FIG. 1, the clock means 10 receives a reset signal 1.
When 4a is input or the pulse signal 10a as a time-up signal is output, the clock is reset to the initial state and the timekeeping operation is stopped.
When the judgment signal 12a is inputted, the timing operation is started and the pulse signal 10a is output after the set time of ΔT has elapsed, and the counting means 11 clears the counting contents when the operation start signal 15a is inputted. is configured to be 15 is a control means that outputs an operation start signal 15a when the power is turned on, and 16 is a signal generation means that outputs a drive signal 16a at a cycle ΔT when the operation start signal 15a is input. It is. Both the peak value detection means 3 and the average value detection means 4 receive the drive signal 1.
6a, it is configured to output a peak value signal 3a and an average value signal 4a, respectively.

Next, the operation of the open phase detection device shown in Fig. 1 will be explained as follows.
This will be explained using the flowchart shown in the figure. First, when power is applied to the control means 15, the signal 15a
is output, the contents of the counting means 11 are cleared to zero, and then the driving signal 16 is output from the signal generating means 16.
Since the signal a is output, the detection means 3 and 4 output a peak value signal 3a and an average value signal 4a, respectively.
Next, the first determination means 12 compares the magnitude A of the peak value signal 3a with the first set current value _I1 , and if A< _I1 , the signal 3a is again output to the first determination means 12 after the elapse of time ΔT. No signal is output from the means 12 until it is input to the signal. If A≧I ₁ in step S ₄ in which the signal 3 a and the set value I ₁ are compared, the signal 12 a is output, so the clocking means 10 starts timing operation, and the reset signal 14 a is input to the means 10 . Unless otherwise specified, the means 10 continues the timekeeping operation and outputs the signal 10a after the time ΔT. Therefore, in step _S6 , the contents of the counting means 11 are incremented by 1. step
In step _S8 following _S4 , the second determination means 13 compares the magnitude A of the signal 3a with the set value _I2 ,
If A<I ₂ , signal 13a is output, so the third
The first reference value _R1 is selected in the determination means 14,
Since the signal 13b is output when A≧I ₂ , the second reference value R ₂ is selected in the determining means 14 (step S ₉ ). Subsequently, in step _S10 , the calculation means 6 calculates the pulsation rate R, and the means 6 outputs the pulsation rate signal 6a of magnitude _R. or R ₂ and R<R ₁ or R<R ₂
If so, the determination means 14 outputs a reset signal 1.
4 is output, so the timekeeping contents of the timekeeping means 10 are reset at this time. In other words, in this case, the clock means 10 is reset without outputting the time-up signal 10a even if it is performing a clock operation.

In FIG. 1, each part operates as described above, so if we assume that no open phase condition has occurred in the electric line 2 and no motor starting current is flowing, the signal 3a
The magnitude A of the signal 1a and the pulsation rate R of the signal 1a are both small, and since I ₁ and R ₁ are set so that A<I ₁ and R<R ₁ in this case, the determination means 12 outputs Since I ₁ < I ₂ , the determining means 13 outputs a signal 13a, and as a result, the determining means 14 outputs a signal 13a because the condition R<R ₁ is satisfied. A reset signal 14a is output. Next, since an open phase condition occurs in the circuit 2, the magnitude of A becomes I ₁ ≦A < I ₂ and R
When ≧R ₁ is reached, the signal 12a is output, and the timer 10 starts a timekeeping operation. On the other hand, the determination means 14 selects the reference value R ₁ , but when R≧R ₁
Therefore, the reset signal 14a is not output from the means 14. Therefore, in this case, since the signal 10a is output after the time ΔT, the occurrence of the open phase state is recognized by this signal. A is I ₁ ≦A
Even if it becomes large enough to satisfy <I ₂ , R≧R ₁ will not occur unless an open phase occurs.
Since R ₁ is set, if a state of I ₁ ≦A < I ₂ occurs even though no open phase has occurred, the timer 10 starts the timer operation, but eventually the calculation means 6 calculates R. The reset signal 14a is sent from the judgment means 14 that has calculated and selected the reference value _R1 before the timer 10 times up for reasons described later.
is output, the signal 10a from the clock means 10
is never output. That is, in this case, the device will not malfunction. The computation time t spent by the computation means 6 is set to ΔT such that t<ΔT in the above case. Next, when the starting current of the motor flows through the electric line 2 and becomes A≧I ₂ , the timing means 10 is started, but the determination means 14 selects the reference value R ₂ and in this case R<R ₂ Since R ₂ is set so that the calculation time t satisfies t<ΔT, the reset signal is sent from the determination means 14 before the timer 10 times up. 14a is output, and as a result, the clock means 10 does not output the signal 10a. That is, in this case, the open phase detection device will not malfunction due to the starting current of the motor.

Since the detection device shown in FIG. 1 operates as described above, when an open phase condition occurs and A≧I ₁ , the signal 10a is always sent after time ΔT regardless of the calculation time t in the calculation means 6. In this case, the actual phase open detection time does not change depending on the values of A and B as in the conventional open phase detecting device described above, and the detecting device shown in Fig. 1 does not change the actual phase open detection time. The detection time is approximately equal to ΔT, and the detection time does not become longer by the calculation time t (t+ΔT), which is the case with the detection time in the conventional open phase detection device. Furthermore, in the detection device shown in FIG. 1, even if the pulsation rate R of the rectified signal 1a temporarily increases due to the starting current of the motor and exceeds the above-mentioned reference value _R1 , the generation of the starting current is
Since the set current value _I2 is detected as a reference and the pulsation rate reference value used as the criterion for determining the occurrence of phase loss at this time is changed to _R2 , which is larger than _R1 , when the motor starting current occurs, There is no possibility that the open phase detection operation will malfunction. Therefore, in such an open phase detection device, the pulsation rate reference values R ₁ and R ₂ can be easily set.

In the above embodiment, the determination means 1 uses the peak value signal 3a to determine the magnitude of the rectified signal 1a.
However, since the average value signal 4a also increases or decreases corresponding to the signal 3a, in the present invention, the signal 4a is inputted to the determination means 12 and 13 instead of the signal 3a. There is no problem.

〔Effect of the invention〕

As described above, the present invention includes three current detection means for detecting each line current in a three-phase circuit; and three current detection means for detecting each line current in a three-phase circuit; phase full-wave rectification means; peak value detection means for outputting a peak value signal according to the peak value of the rectified signal; average value detection means for outputting an average value signal according to the average value of the rectified signal;
A first determining means that compares the value of the signal to be determined, which is one of the peak value signal and the average value signal, with a built-in first set current value, and outputs a first determination signal when the former is greater than or equal to the latter. A second circuit that compares the value of the signal to be determined with a built-in second set current value, and outputs a 21st determination signal if the former is less than the latter, and outputs a 22nd determination signal if the former is greater than or equal to the latter. determining means; calculating means for performing calculations using the peak value signal and the average value signal and outputting a pulsation rate signal according to the pulsation rate of the rectified signal; and determining whether a reset signal is input or a time-up signal is output. a timekeeping means that is then reset to the initial state and stops the timekeeping operation, starts the timekeeping operation when the first determination signal is input, and outputs the time-up signal after a set time elapses;
A first reference value and a second reference value are provided, and when the 21st determination signal is input, the value of the pulsation rate signal and the first
When the pulsation rate signal is compared with the second reference value and the former is less than the latter, the reset signal is output, and when the 22nd judgment signal is input, the value of the pulsation rate signal is compared with the second reference value and the former is lower than the latter. A third determining means outputs the reset signal if the time-up signal is not satisfied, and the phase-opening detection device is configured to detect the occurrence of a phase-opening in the three-phase electric circuit using the time-up signal. As a result, the calculation time of the pulsation rate in the calculation means is prevented from affecting the open phase detection time, and as a result, the open phase detection time almost coincides with the set time in the time measurement means, and the rectified signal This has the effect of providing an open phase detection device that does not change depending on the peak value or average value of . Also, if the peak value or average value of the rectified signal is small,
The pulsation rate reference value as a criterion for open phase determination is set to the first reference value, which is a small value, but if the peak value or average value of the rectified signal increases due to starting the motor, etc., the pulsation rate The rate reference value is set to a second reference value that is larger than the first reference value, and the open phase detection device is prevented from malfunctioning when starting the motor, etc. As a result, the open phase detection device can easily set the pulsation rate reference value. There is an effect that the device can obtain.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of an embodiment of the present invention, Fig. 2 is a flowchart for explaining the operation of Fig. 1, Fig. 3 is a block diagram of a conventional open phase detection device, and the X diagram in Fig. 4.
The Y diagram and the Z diagram are different waveform diagrams of main parts in FIG. 3, respectively. 1... Three-phase full-wave rectification means, 1a... Rectification signal,
2... Three-phase electric circuit, 3... Peak value detection means, 3a...
... Peak value signal, 4... Average value detection means, 4a...
Average value signal, 6... Calculating means, 6a... Pulsation rate signal, 10... Timing means, 10a... Time up signal, 12... First judgment means, 12a... First judgment signal, 13... Second Judgment means, 13a...21st
Judgment signal, 13b... 22nd judgment signal, 14... Third judgment means, 14a... Reset signal, CT ₁ -
CT ₃ ...Current transformer.

Claims (1)

[Claims] 1. first to third current detection means for detecting each line current in the three-phase electric circuit; phase full-wave rectification means; peak value detection means for outputting a peak value signal according to the peak value of the rectified signal; average value detection means for outputting an average value signal according to the average value of the rectified signal; The value of the signal to be determined, which is one of the peak value signal and the average value signal, is compared with a built-in first set current value, and the value of the signal to be determined is determined to be the same as the first set current value.
a first determination means for outputting a first determination signal when the current value is equal to or greater than a set current value; comparing the value of the determined signal with a built-in second set current value, and determining that the value of the determined signal is the second set current value; a second determination means that outputs a 21st determination signal when the value of the determined signal is less than the second set current value; and outputs a 22nd determination signal when the value of the determined signal is equal to or greater than the second set current value; a calculation means for performing a predetermined calculation using the value signal and outputting a pulsation rate signal corresponding to the pulsation rate of the rectified signal; when a reset signal is input or a time-up signal is output, the rectification signal is reset to the initial state; a timekeeping means for stopping the timekeeping operation when the first determination signal is input, and for starting the timekeeping operation when the first determination signal is input, and outputting the time-up signal after a set time elapses; a first reference value and a second reference value are provided; and when the 21st determination signal is input, the value of the pulsation rate signal is compared with the first reference value, and if the value of the pulsation rate signal is less than the first reference value, the reset signal is sent. and when the 22nd determination signal is input, the value of the pulsation rate signal is compared with the second reference value, and if the value of the pulsation rate signal is less than the second reference value, the and third determining means for outputting a reset signal, and detects the occurrence of an open phase in the three-phase electric circuit based on the time-up signal.