JP3700744B2 - Power supply phase loss detection circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power supply phase loss detection circuit for an AC power supply, and more particularly, to a power supply phase loss detection circuit that can easily determine whether or not an AC power supply has a phase loss and can identify the phase loss.
[0002]
[Prior art]
An example of a conventional power supply phase loss detection circuit for a three-phase AC power supply is shown in FIG. In FIG. 4, the power supply phase loss detection circuit of this conventional example is a converter circuit using a switching element such as a thyristor for converting a U-phase, V-phase, and W-phase three-phase AC power source into P-phase and N-phase DC voltages. 101 and a circuit having a smoothing main capacitor (not shown) connected to the output side of the converter circuit 101. The comparators 401 to 403 and the 3-input NAND gate circuit 404 are connected to each other. It is prepared for.
The power supply phase loss detection circuit of this conventional example inserts comparators 401 to 403 between all three phases of U phase, V phase, and W phase (between UW, UV, and VW), respectively. It monitors and detects open phases. More specifically, one of the comparators 401 to 403 malfunctions through a filter circuit (not shown) that removes an AC component by full-wave rectifying the U-phase, V-phase, and W-phase voltages. The phase loss detection signal SC is generated by calculating the logical sum of whether the signal is detected. Since the outputs of the comparators 401 to 403 are negative logic signals indicating abnormality detection at the “L” level, the logical sum is obtained by the three-input NAND gate circuit 404.
[0003]
[Problems to be solved by the invention]
However, the above-described conventional power supply phase loss detection circuit requires a comparator and a filter circuit between all three phases, so that the number of components constituting the power supply phase loss detection circuit is large and the circuit cost is high. there were.
The present invention has been made in view of the above-described conventional problems, and is intended to provide a power supply phase loss detection circuit that can easily determine whether there is a phase loss in an AC power source at low cost and identify the phase loss. It is aimed.
[0004]
[Means for Solving the Problems]
In order to solve the above problem, an invention according to claim 1 of the present application is a power supply phase loss detection circuit that detects a phase loss of an n-phase (n is a positive integer) AC power source.
Rectification means for rectifying the output voltage of the AC power supply and measurement of the rise time of the output voltage of the rectification means when the AC power supply is turned on to detect that any phase of the AC power supply is abnormal And a phase detection means.
According to a second aspect of the present invention, in the power supply phase loss detection circuit,
The phase loss detection means includes an analog / digital conversion means for converting the output voltage of the rectification means into a digital value, and the output voltage of the AC power supply from the input of the AC power supply based on the output of the analog / digital conversion means. Measuring means for measuring a time until the voltage reaches a predetermined voltage, and detecting that there is an abnormality in any phase of the AC power source based on a measurement result of the measuring means Is.
As described above, in the power supply phase loss detection circuit of the present invention, the phase loss detection unit measures the rise time of the output voltage of the rectification unit when the AC power supply is turned on, and any phase of the AC power supply is abnormal. More specifically, the output voltage of the rectifying means is converted into a digital value by the analog / digital conversion means, and the AC power supply is turned on based on the output of the analog / digital conversion means. The time until the output voltage of the AC power supply reaches a predetermined voltage is measured by the measuring means, and based on the measurement result of the measuring means, it is detected that any phase of the AC power supply is abnormal. Therefore, the DC voltage obtained by rectifying the AC power supply voltage is used, for example, as a power supply for a servo drive or an inverter. In these devices, a switching element is used. An MPU (microprocessor) or the like is provided as a control means for performing the ignition control or the like. For example, the measurement means of the phase loss detection means is a software timer, and the abnormality detection processing in the phase loss detection means is performed by the MPU or the like. If it is realized by a program executed by, the only component that needs to be newly added to perform phase loss detection is analog / digital conversion means, and the number of parts is reduced compared to the conventional configuration. Therefore, it is possible to realize a power supply phase loss detection circuit that can determine the phase loss of the AC power supply easily and at low cost, and can identify the phase loss.
[0005]
DETAILED DESCRIPTION OF THE INVENTION
DESCRIPTION OF EMBODIMENTS Hereinafter, embodiments of a power supply phase loss detection circuit of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a configuration diagram of a power supply phase loss detection circuit according to an embodiment of the present invention. In the figure, the same reference numerals are given to the portions overlapping with FIG. 4 (conventional example).
In FIG. 1, the power supply phase loss detection circuit of this embodiment uses a switching element such as a thyristor as a rectifying means for converting a U-phase, V-phase, and W-phase three-phase AC power source into P-phase and N-phase DC voltages. The present invention is applied to a circuit including the converter circuit 101 used and a smoothing main capacitor 102 connected to the output side of the converter circuit 101, and includes P-phase and N-phase DC voltages (inter-PN voltages). A / D converter 103 that converts (VPN) into a digital value, and a three-phase AC power supply by a power supply phase loss detection processing program based on the inter-PN voltage (digital value) VPN fetched from the A / D converter 103 The CPU 104 is configured to measure the rise time of the inter-PN voltage VPN at and to detect that there is an abnormality in any phase of the three-phase AC power supply.
FIG. 2 is an explanatory diagram illustrating the rising characteristics of the inter-PN voltage VPN when the three-phase AC power supply has no phase failure and when there is a phase failure. As shown in the figure, for example, if the V phase is lost due to a disconnection or the like, the three-phase AC power supply is connected to only a single phase, so the power supply capacity becomes 1/3, so there is no missing phase. The rise time Tf of the PN voltage VPN at the time of abnormality with a phase failure takes three times as long as the rise time TS 'until the predetermined voltage VS of the PN voltage VPN at the normal time is reached. .
The power supply phase loss detection processing program in the CPU 104 pays attention to the difference in the rising characteristics of the inter-PN voltage VPN between the normal state without such a phase loss and the abnormality with the phase loss. Based on the output (inter-PN voltage VPN), the time from when the three-phase AC power supply is turned on until the inter-PN voltage VPN reaches the predetermined voltage VS is measured by a measuring means such as a software timer. It detects that there is an abnormality in any phase of the power supply.
FIG. 3 shows a flowchart of the power supply phase loss detection processing program. In the figure, when the three-phase AC power is turned on in step S301, the software timer value Tm is reset in step S302.
Next, in steps S303 and S304, the inter-PN voltage VPN is taken from the A / D converter 103 at predetermined time intervals, and it is determined whether or not the inter-PN voltage VPN exceeds the predetermined voltage VS. The processes in steps S303 and S304 are repeated until the inter-PN voltage VPN exceeds the predetermined voltage VS.
In step S304, when the inter-PN voltage VPN exceeds the predetermined voltage VS, the process proceeds to step S305, and the software timer value Tm is fetched. In step S306, the software timer value Tm is compared with the predetermined time TS. Here, the predetermined time TS is set to a value slightly larger than the rising time TS ′ until the predetermined voltage VS of the inter-PN voltage VPN is reached when there is no phase loss.
That is, if the software timer value Tm is smaller than the predetermined time TS in the comparison determination in step S306, it is determined that the three-phase AC power supply is in a normal state with no phase loss (step S307). If Tm is larger than the predetermined time TS, it is determined that the three-phase AC power supply is in an abnormal state with a phase failure (step S308).
The DC voltage (inter-PN voltage VPN) obtained by rectifying the U-phase, V-phase, and W-phase three-phase AC power supply voltages by the converter circuit 101 is used, for example, as a power supply for servo drives and inverters. In the apparatus, a CPU or the like is already provided as a control means for performing ignition control of a switching element (inverter or the like), and as in this embodiment, the measurement means of the phase loss detection means is a software timer, If the abnormality detection process in the phase loss detection means is realized by a program executed by the CPU or the like, the A / D converter 103 is the only component to be newly added to perform phase loss detection. Compared to the conventional configuration, the number of parts can be reduced, and the power supply phase loss detection can be performed at low cost and easily to determine whether there is a phase failure in the AC power supply. It is possible to realize the road.
Also, in servo drive and inverter devices, the rectified PN voltage VPN must always be discharged through a resistor for regulation, that is, when the voltage exceeds a certain level due to the generation of regenerative energy of the motor. It is configured to be monitored. Such a monitoring function of the inter-PN voltage VPN is realized by a comparator as in the conventional power supply phase loss detection circuit. In the present embodiment, it is possible to constantly monitor the PN voltage VPN by taking in the output of the A / D converter 103. That is, according to the configuration of the present embodiment, not only the power supply phase loss detection but also the PN voltage VPN can be constantly monitored. As a result, the number of parts of the entire apparatus can be reduced, and the cost of the apparatus can be reduced. Can be achieved.
[0006]
【The invention's effect】
As described above, according to the power supply phase loss detection circuit of the present invention, the phase loss detection unit measures the rise time of the output voltage of the rectification unit when the AC power supply is turned on, and sets it to any phase of the AC power supply. In particular, an abnormality is detected, and in particular, the output voltage of the rectifying means is converted into a digital value by the analog / digital conversion means, and the AC power supply is turned on based on the output of the analog / digital conversion means. The time until the output voltage reaches a predetermined voltage is measured by the measuring means, and based on the measurement result of the measuring means, it is determined that there is an abnormality in any phase of the AC power supply. If the measurement means of the phase loss detection means is realized by a software timer and the abnormality detection processing in the phase loss detection means is realized by a program executed by an MPU or the like. Since MPUs and the like are often already provided to control the system that uses the output voltage of the rectifier, the component that should be newly added to detect the phase loss is analog / digital conversion. Provided is a power supply phase loss detection circuit that can reduce the number of parts compared to the conventional configuration, can easily determine whether there is a phase loss in an AC power source, and can identify the phase loss. be able to.
[Brief description of the drawings]
FIG. 1 is a configuration diagram of a power supply phase loss detection circuit according to an embodiment of the present invention.
FIG. 2 is an explanatory diagram illustrating the rise of the voltage between PN when there is no phase loss (normal) and when there is a phase failure (abnormal) in the three-phase AC power supply;
FIG. 3 is a flowchart illustrating power supply phase loss detection processing in the CPU according to the embodiment.
FIG. 4 is a configuration diagram of a conventional power supply phase loss detection circuit.
[Explanation of symbols]
101 Converter circuit (rectifying means)
102 Main capacitor 103 A / D converter (analog / digital conversion means)
104 CPU (phase loss detection means, measurement means)
401-403 Comparator 404 3-input NAND gate circuit

Claims (2)

In a power supply phase loss detection circuit that detects phase loss of an n-phase (n is a positive integer) AC power source,
Rectifying means for rectifying the output voltage of the AC power supply;
And a phase failure detecting means for measuring a rise time of the output voltage of the rectifying means when the AC power is turned on and detecting that any phase of the AC power is abnormal. Phase loss detection circuit. In the power supply phase loss detection circuit,
The phase loss detection means includes
Analog / digital conversion means for converting the output voltage of the rectifying means into a digital value;
Measuring means for measuring the time from when the AC power supply is turned on until the output voltage of the AC power supply reaches a predetermined voltage, based on the output of the analog / digital conversion means;
2. The power supply phase loss detection circuit according to claim 1, wherein an abnormality is detected in any phase of the AC power supply based on a measurement result of the measurement means.

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