CN100588977C - Method and device for lack of zero detection for three phase circuit - Google Patents
Method and device for lack of zero detection for three phase circuit Download PDFInfo
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- CN100588977C CN100588977C CN200610075054A CN200610075054A CN100588977C CN 100588977 C CN100588977 C CN 100588977C CN 200610075054 A CN200610075054 A CN 200610075054A CN 200610075054 A CN200610075054 A CN 200610075054A CN 100588977 C CN100588977 C CN 100588977C
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Abstract
The device for detecting lack of zero line includes a current transformer. Zero line of three-phase equipment passes through the current transformer. The output end of the current transformer is connected to a light coupling input port. A guard signal for lack of zero line is sent out after the signal process circuit processes the output from the light coupler. Since detecting lack of zero line isimplemented by determining whether there is current on zero line without need to know magnitude of current on zero line, the invention overcomes the issue of low precision and resolution of former detection method. Moreover, current transformer with high precision is not needed; or generic current transformer is utilized in the invention so as to lower cost greatly.
Description
Technical field
The present invention relates to a kind of zero detection method and device that lack of three-phase circuit, in particular, a kind of being used for detected method and the device whether zero line breaks at the three-phase four-wire system circuit.
Background technology
Its zero line of equipment for three-phase four-wire system in the prior art is absolutely necessary, if zero line disappearance or break when equipment work will make the equipment can't operate as normal even damage, is very important so lack zero protection for the three-phase and four-line control equipment.To detect is a comparatively problem of difficulty but lack at present zero, conventional detection often exist detection less than or flase drop survey, problems such as mistake alarm take place.
In three-phase system, want to detect zero line and fall, see it is nothing but that the electric current and voltage difference of system is set about when zero line has or not, provide the judgement signal according to this species diversity from the angle of circuit.
But because the existence of each phase input impedance of three-phase equipment, even zero line has fallen, each relative zero line still has certain voltage, and because the uncertainty of three-phase voltage, such a case might occur fully: before and after zero line had fallen, the voltage of each relative zero line did not change.Therefore, whether fall to be difficulty very for utilize detecting zero line that voltage method detects three-phase equipment.
When zero line falls, notable feature be exactly the electric current of input zero line be zero.The method that general detection zero line falls all is to detect neutral line current, size according to neutral line current judges whether it is that zero line falls, and still most of three-phase and four-line control equipment is in unloaded operation, and neutral line current is very little, and when the work of being fully loaded with, neutral line current but can be quite big.Lack zero testing circuit and should guarantee can work under equipment is fully loaded, not alarm by mistake also will guarantee can detect when equipment lacks zero when equipment was unloaded, and this has just proposed quite high requirement to precision and the resolution that lacks zero testing circuit.
Zero detection method that lacks commonly used at present has following several:
1, scarce zero detection method of series connection sampling resistor on the three-phase equipment zero line
On zero line, when flowing through resistance, neutral line current will produce pressure drop with resistance string.By the pressure drop on the sampling resistor, can obtain the size of neutral line current, thereby judge whether zero line breaks, and its principle as shown in Figure 1.
But be to use this method, the specification of resistance will be difficult to select, and electric current is very big when being fully loaded with work owing to the three-phase and four-line control equipment, can reach tens even the hundreds of ampere, under the so big electric current, the resistance of resistance can only be chosen the milliohm level, otherwise resistance will be too warm.But when zero load, neutral line current is generally below 1 ampere, and ohmically like this voltage just has only several millivolts, and so low voltage signal is easy to be subjected to external disturbance, causes detecting failure, produces mistake alarm etc.And if increase resistance, though the voltage signal when zero load has improved, the ohmically loss of full load will very big, resistance heating is severity very.This in addition detection method does not have connecting together of isolation with power circuit and testing circuit, easily consumer is caused interference.
2, use zero detection method that lacks of current sensor sampling neutral line current size
The use current sensor also can detect the size of neutral line current, and judges whether zero line according to the size of neutral line current, and its principle as shown in Figure 2.Current sensor generally is to adopt Hall current sensor or current transformer.
This method does not have the problem of resistance heating, and solved the problem that testing circuit and power circuit are not isolated, but still can't overcome the not high problem of accuracy of detection and resolution, in order to distinguish the state of equipment no-load running state and neutral line break accurately, the precision of sensor must be very high, and high-grade sensor price is more expensive, and this has improved the cost of equipment.
Therefore, prior art awaits to continue to improve and development.
Summary of the invention
The object of the present invention is to provide a kind of zero detection method and device that lack of three-phase circuit, exactly in order to overcome the problem of accuracy of detection and resolution in the prior art, a kind of new scarce zero detection method and device proposed, only need to judge having or not of neutral line current, and need not to know that the size of neutral line current can realize lacking zero detection, it has overcome the precision of existing detection method existence and the problem of resolution, also is easy to simultaneously realize that cost is low, reliability is high.
Technical scheme of the present invention comprises:
A kind of scarce zero pick-up unit of three-phase circuit; wherein; it comprises a current transformer; the zero line of described three-phase equipment passes from this current transformer; the output terminal of this current transformer is received an optocoupler input port, and the output of this optocoupler is sent through the processing of a signal processing circuit and lacked zero guard signal.
Described device wherein, also is provided with a freewheeling circuit between described current transformer and the described optocoupler input port.
Described device wherein, also is provided with a rectification circuit between described current transformer and the described optocoupler input port.
Described device, wherein, described signal processing circuit comprises a positive voltage that is arranged on the described optocoupler output port, and one lacks the zero-signal line by described optocoupler triode connection, the electric capacity and the resistance that are arranged in parallel on the described scarce zero-signal line.
A kind of scarce zero detection method of three-phase circuit, it comprises step:
The signal processing circuit of an optocoupler and optocoupler output terminal oral-lateral is set; the zero line of described three-phase equipment passes from a current transformer; the output of this current transformer is connected to this optocoupler input port, and the processing of the output process signal processing circuit of this optocoupler has or not according to the electric current in the zero line circuit sends scarce zero guard signal.
Scarce zero detection method and the device of a kind of three-phase circuit provided by the present invention, compared with prior art, can realize lacking zero and detect owing to only judge having or not of neutral line current, and need not to know and the size of neutral line current overcome original detection method precision and the not high problem of resolution; Owing to need not accurately to measure the neutral line current size, also just do not need to use the current with high accuracy sensor in addition, use general current transformer to get final product, cost also reduces greatly.
Description of drawings
Fig. 1 be in the prior art on zero line the synoptic diagram that lacks zero detection method of series connection sampling resistor;
Fig. 2 is the synoptic diagram that lacks zero detection method that uses current sensor sampling neutral line current size in the prior art;
Fig. 3 is a circuit theory synoptic diagram of the present invention;
Fig. 4 is the present invention adds freewheeling circuit between current transformer secondary and optocoupler input port a circuit theory synoptic diagram;
Fig. 5 is the present invention adds rectification circuit between current transformer secondary and optocoupler input port a circuit theory synoptic diagram;
Fig. 6 is for cooperating the synoptic diagram of a simple signal processing circuit of the present invention;
Fig. 7 is the synoptic diagram of a specific embodiment of the present invention.
Embodiment
Below in conjunction with accompanying drawing, will be described in further detail each preferred embodiment of the present invention:
Because the existing thought that lacks zero detection method all is by a kind of current detection circuit, detects the size of three-phase circuit neutral line current, the size according to neutral line current judges whether to take place neutral line break then.Because need detect the size of neutral line current,, also inevitably there is the problem of sampling precision and resolution simultaneously so need current with high accuracy sensor and sample circuit.But judge whether break zero line only need to know that neutral line current has or not just passable, do not need to know the size of neutral line current.According to this thought, the present invention proposes a kind of zero detection method and device that lack of new three-phase circuit, it has overcome the precision that existing detection method exists and the problem of resolution, also is easy to simultaneously realize that cost is low, reliability is high.
Zero detection method that lacks of three-phase circuit of the present invention is, zero line is passed from current transformer, the output of current transformer is directly received or is received the optocoupler input port by resistance, electric capacity, diode, stabilivolt, having or not of neutral line current causes having or not of current transformer secondary current, thereby cause flowing through the having or not of electric current of optocoupler diode, thereby the variation that the triode that makes optocoupler produces break-make can judge according to the break-make variation of optocoupler output port whether zero line opens circuit then.
Three-phase circuit of the present invention lack the signal processing circuit that zero pick-up unit comprises a current transformer, optocoupler and optocoupler output terminal oral-lateral; The zero line of three-phase equipment passes from current transformer, and the output of current transformer is directly received or received the optocoupler input port by resistance, electric capacity, diode, stabilivolt, and the output of optocoupler is sent through the processing of signal processing circuit and lacked zero guard signal.
Whether the key of the inventive method is having or not of neutral line current to be converted into flow through having or not of optocoupler diode current, thereby is converted into the break-make of optocoupler triode, can obtain zero line according to the break-make situation of optocoupler triode and break.
Fig. 3 is a circuit theory synoptic diagram of the present invention.The zero line of three-phase equipment passes from current transformer, and the output of current transformer is directly received or received the optocoupler input port by resistance, electric capacity, diode, stabilivolt, and the output of optocoupler is sent through the processing of signal processing circuit and lacked zero guard signal.
When in the zero line electric current being arranged, will generate electric current at the current transformer secondary, and form the loop with the diode of optocoupler.When zero line did not have electric current, the current transformer secondary did not just have electric current yet, and the diode of same optocoupler does not just have electric current yet.And the characteristic of optocoupler is if diode has electric current to flow through, and triode will conducting; Diode does not have electric current to flow through, and triode just turn-offs.Like this when in the zero line electric current being arranged, the optocoupler triode is exactly conducting; When not having electric current in the zero line, the optocoupler triode turn-offs; Neutral line current have or not the break-make that is converted into the optocoupler triode.
Because neutral line current generally is an alternating current, then the electric current of current transformer secondary generally also is an alternating current, in order to make the current transformer operate as normal, generally need between current transformer secondary and optocoupler input port, add freewheeling circuit or rectification circuit, its synoptic diagram such as Fig. 4, shown in Figure 5.
Be the circuit theory diagrams that between current transformer secondary and optocoupler input port, add freewheeling circuit as shown in Figure 4.When neutral line current is alternating current, also generate alternating current at the current transformer secondary, this alternating current can form the loop by fly-wheel diode or optocoupler diode.
Be the circuit theory diagrams that between current transformer secondary and optocoupler input port, add rectification circuit as shown in Figure 5.When neutral line current is alternating current, also generate alternating current at the current transformer secondary, this alternating current becomes DC current through behind the rectification circuit, and forms the loop by the optocoupler diode.
Neutral line current is that alternating current also brings a problem, be exactly always neutral line current has passing zero moment, that is to say, under normal circumstances, the optocoupler triode also has the situation of break-make.Need do Filtering Processing to the output signal of optocoupler at optocoupler output terminal oral-lateral for this reason, having or not of neutral line current changed into the scarce zero-signal of high-low level, make having or not that the scarce zero-signal of its output can the correct response neutral line current.
As Fig. 6 is the synoptic diagram of a simple signal processing circuit.When zero line has electric current, the conducting of optocoupler triode, to capacitor C 1 charging, scarce zero-signal is a high level to power Vcc by R1; When zero line did not have electric current, capacitor C 1 was by the R2 discharge, and scarce zero-signal is a low level; When neutral line current was interchange, the value of choose reasonable R1, R2, C1 made charging rate ζ
1=R1C1 is less than discharge time constant ζ
2=R2C1 can make the of short duration zero passage of neutral line current can not cause lacking the variation of zero-signal.This selection that discharges and recharges time constant must be suitable, and charging rate should be as far as possible little under the condition that satisfies optocoupler triode through-current capacity limit value; And discharge time constant is crossed conference to cause lacking the zero-signal response too slow, too small then mistake alarm easily, because neutral line current is generally the 3n subharmonic of mains frequency in the three-phase system, discharge time constant is generally got 10ms and is got final product.
Because the current source characteristic of current transformer, even in the three-phase equipment zero load, neutral line current is less than 1A, and under the situation of current transformer secondary current less than 1mA, the electric current that flows through the optocoupler diode still exists.If it is too small but to flow through the electric current of optocoupler diode, also will be difficult to make the conducting of optocoupler triode, need to open the turn ratio of the appropriate selection current transformer of electric current in use, make the electric current that when three-phase equipment no-load running, flows through the optocoupler diode can make the reliable conducting of optocoupler triode according to the minimum of the no-load current of three-phase equipment and optocoupler.
Be the circuit complete diagram of a specific embodiment of the present invention as shown in Figure 7; wherein the zero line of three-phase equipment passes from current transformer; the output of current transformer is received the optocoupler input port through behind the rectification circuit; the output of optocoupler is sent through the processing of signal processing circuit and is lacked zero guard signal, and R1, R2, C1 are respectively 1K, 100K, 0.1uF in the signal processing circuit of this embodiment.
Therefore, the inventive method and device can realize that by simple circuit theory its circuit is easy to realize that cost is low, reliability is high to the zero judgement of lacking of three-phase circuit; But must be understood that above-mentioned description at specific embodiment is comparatively concrete, can not therefore be interpreted as the restriction to scope of patent protection of the present invention, scope of patent protection of the present invention should be as the criterion with claims.
Claims (5)
1, a kind of scarce zero pick-up unit of three-phase circuit; it is characterized in that; it comprises a current transformer; the zero line of described three-phase circuit passes from this current transformer; the output terminal of this current transformer is received an optocoupler input port, and the output of this optocoupler is sent through the processing of a signal processing circuit and lacked zero guard signal.
2, device according to claim 1 is characterized in that, also is provided with a freewheeling circuit between described current transformer and the described optocoupler input port.
3, device according to claim 1 is characterized in that, also is provided with a rectification circuit between described current transformer and the described optocoupler input port.
4, device according to claim 1, it is characterized in that, described signal processing circuit comprises a positive voltage that is arranged on the described optocoupler output port, and one lacks the zero-signal line by the connection of the optocoupler triode in the optocoupler, the electric capacity and the resistance that are arranged in parallel on the described scarce zero-signal line.
5, a kind of scarce zero detection method of three-phase circuit, it comprises step:
The signal processing circuit of an optocoupler and optocoupler output terminal oral-lateral is set; the zero line of described three-phase circuit passes from a current transformer; the output of this current transformer is connected to this optocoupler input port, and the processing of the output process signal processing circuit of this optocoupler has or not according to the electric current in the zero line circuit sends scarce zero guard signal.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN200610075054A CN100588977C (en) | 2005-12-20 | 2006-03-21 | Method and device for lack of zero detection for three phase circuit |
Applications Claiming Priority (3)
| Application Number | Priority Date | Filing Date | Title |
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| CN200510121055.9 | 2005-12-20 | ||
| CN200510121055 | 2005-12-20 | ||
| CN200610075054A CN100588977C (en) | 2005-12-20 | 2006-03-21 | Method and device for lack of zero detection for three phase circuit |
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| CN1987498A CN1987498A (en) | 2007-06-27 |
| CN100588977C true CN100588977C (en) | 2010-02-10 |
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Families Citing this family (7)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN103326332A (en) * | 2012-03-23 | 2013-09-25 | 苏州工业园区新宏博通讯科技有限公司 | Three-phase four-wire circuit |
| CN106405305B (en) * | 2015-07-30 | 2024-02-27 | 浙江正泰电器股份有限公司 | Zero line phase failure detection circuit and method for detecting zero line phase failure |
| CN105486936B (en) * | 2015-12-04 | 2019-06-14 | 易事特集团股份有限公司 | Uninterruptible power supply with scarce zero curve detection circuit |
| CN108562818B (en) * | 2017-12-21 | 2020-08-11 | 科华恒盛股份有限公司 | Zero line open circuit detection method and device of UPS and UPS |
| CN109490815B (en) * | 2018-09-27 | 2020-10-27 | 宁波三星智能电气有限公司 | Three-phase ammeter broken zero line detection circuit and detection method thereof |
| CN109358310B (en) * | 2018-12-03 | 2024-03-22 | 烟台东方威思顿电气有限公司 | Device and method for detecting broken zero line of three-phase four-wire electric energy meter |
| CN109931287B (en) * | 2019-04-10 | 2020-06-12 | 深圳市恩玖科技有限公司 | Fault detection circuit of alternating current fan and fault detection method thereof |
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