The present invention relates to a kind of current transformers, are mainly used in the current measurement of intelligent electric meter industry.
Currently, the current measurement circuit of intelligent electric energy meter industry, generallys use manganese copper diverter and electromagnetic type Current Mutual Inductance
Copper-manganese current divider type current sensor is low in cost, its working principle is that electric resistance partial pressure, since the resistance value of copper-manganese is with temperature
The variation of degree is smaller, but discreteness is bigger, therefore, is generally used in 2.0 grades of single-phase electric energy meter.To common 220V 5
(60) electric energy meter of A, sample resistance resistance value are about calorific value about 1~2W between 250~500 μ Ω.
The advantages of manganese copper diverter, is: the processing is simple, it is low in cost, DC component and higher hamonic wave can be measured.Frequently
Rate characteristic can stablize transmission from DC-1MHz signal and (be limited by ammeter measurement loop sample rate, actual use range usually exists
25kHz or less).
The shortcomings that manganese copper diverter is: 1, resistance heating amount is big when high current, if screw crimping is loosely when terminal assembles
Gu radiating treatment is improper, it is easy to burn out ammeter.2, due to metal component and processing, cause resistance discrete
Property it is larger, although resistance value varies with temperature small, but irregularly changed by temperature, therefore, be not suitable for high-precision measuring.
Since voltage and current signals common end can not separate (see Fig. 1), cannot directly by single-phase three-wire, two line of two-phase,
Two-phase, three-wire, phase three-wire three, three-phase and four-line etc. need in the application environment of multichannel electric current sampling and measuring.
It will be seen from figure 1 that using the electric energy meter of manganese copper diverter, firewire L is made as the reference " ground " of measurement loop
(metering chip pressure resistance generally in 5V hereinafter, if voltage input is used firewire L, and using zero curve N as ground wire,
Then the pressure difference of two simulation inputs of metering chip is up to 220VAC, and chip cannot withstand), manganese copper diverter is " hard with firewire
Current transformer is according to electromagnetic induction principle.As shown in Fig. 2, current transformer be iron core by being closed and around
Group composition, its first winding the number of turns is seldom, goes here and there in the route for the electric current for needing to measure, therefore it often has the whole of route
Electric current flows through, and secondary winding turn ratio is more, is serially connected in measuring instrumentss and protective loop, current transformer at work, it
Secondary circuit be closure always, therefore the impedance very little of measuring instrumentss and protective loop series coil, current transformer
The close short circuit of working condition.The advantages of mutual inductor is that the linearity is good, and stability is high, and accuracy hardly follows temperature change, especially
It is suitble to the measurement of degree of precision (0.5S grades).
Reference end using the current sampling of the electric energy meter of current transformer is connected in secondary side with zero curve, therefore primary side
It is to be isolated (see Fig. 3) that electric current input, which is with voltage circuit, and therefore, the reference end of metering chip can be zero curve N, is measured in this way
The voltage difference of multiple analog input ends of chip will control in 2V hereinafter, common 5V or less the operating voltage of chip permission model
In enclosing.Voltage and the cut-in method being galvanically isolated are particularly suitable for the application for requiring more than two current loops to measure, such as two
Phase table, phase three-wire three table and three-phase and four-line table etc..
The shortcomings that mutual inductor is: volume is big, at high cost, anti-overload ability is weak, can measure the frequency range of signal generally not
It cannot open a way more than 2.5kHz, especially secondary side current measurement circuit, otherwise can generate high voltage and damage measurement electricity
Summary of the invention
It is above-mentioned it is an object of the invention to overcome the problems, such as, a kind of current transformer is provided, both there is copper-manganese to shunt
The characteristic of low cost of device, and the separation with mutual inductor similar current loop and voltage circuit, are conducive to be greatly reduced three
The volume and weight of phase intelligent electric meter, reduces cost.
The object of the present invention is achieved by the following technical solutions,
Current transformer, it includes sensing head, flow guide bar and C-shaped magnetic yoke, wherein
Sensing head, output end connect current sampling circuit；
Flow guide bar passes through C-shaped magnetic yoke, and both ends are separately connected firewire end of incoming cables and firewire leading-out terminal, in C after being used to be powered
Alternating magnetic field is generated between two ends of shape magnetic yoke；
C-shaped magnetic yoke, the sensing head are inserted by the open end of C-shaped magnetic yoke, make C-shaped magnetic yoke that the sensing be completely covered
Head induces electromotive force in the sensing head output end using the alternating magnetic field.
C-shaped insulating trip identical with its opening direction is inserted in the open end of the C-shaped magnetic yoke, the sensing head is inserted into C
The open end of shape insulating trip makes C-shaped magnetic yoke and C-shaped insulating trip that the sensing head be completely covered；The flow guide bar from C-shaped magnetic yoke and
It is passed through in the enclosed cavity of C-shaped insulating trip.
The sensing head is an air core solenoid formed using conducting wire uniform winding, which connects institute
State current sampling circuit.
The internal diameter of the air core solenoid is 0.5-1.5mm, and winding the number of turns is 1-10 circle.
The air core solenoid is fixed on the pcb board where the current sampling circuit with embedded mode.
The sensing head is that the planar spiral-type directly printed on the pcb board of the current sampling circuit place or plane are more
The spiral PCB type air core coil of side shape.
Described PCB type air core coil the number of turns is 3 circles, internal diameter 0.5-2mm, outer diameter 4.5mm.
The flow guide bar includes that sequence is connected to form the end of incoming cables linkage section of U-shaped, induction section, leading-out terminal linkage section；Wherein
End of incoming cables linkage section connects firewire end of incoming cables, and leading-out terminal linkage section connects firewire leading-out terminal, and induction section passes through the C-shaped magnetic yoke,
So that the C-shaped magnetic yoke at least covering part incudes section, forms flow guide bar and C-shaped magnetic yoke mutually hooks the arrangement states of drawing.
The C-shaped magnetic yoke is made of permalloy, microcrystallizing alloy or silicon steel sheet.
The C-shaped magnetic yoke is made into integration using permalloy, or is formed by stacking using microcrystallizing alloy or permalloy, or
Person is formed by stacking using silicon steel sheet.
The present invention has the following advantages compared with prior art and effect:
1, the present invention replaces iron core and winding using the more simple small and exquisite sensing head of structure, reduces precious metal material
The consumption of (copper), alleviates weight, reduces volume.2, voltage and current loop in polyphase ac electrical measurement are easily achieved
Primary side electrical separation simplifies the power supply design of sample circuit.3, sensing head is fixed on the pcb board with embedded mode
(air core solenoid), or directly print in (planar spiral-type or plane polygon helical winding) on the pcb board, so that
Mutual inductor can be built in inside electric energy meter in the case where only taking up very little inner space, to greatly reduce the whole of electric energy meter
Body volume.4, due to being free of iron core, the present invention significantly improves without hysteresis effect and magnetic saturation phenomenon, bandwidth.5, sensing head
It is not electrically connected, tested circuit is influenced minimum between tested electric current.6, dynamic range is wider, is able to solve electrified iron
The electrical energy measurement problem of the impact loads such as road, large-scale electromagnetic oven.7, at low cost.
Detailed description of the invention
Fig. 1 is the ammeter measurement loop schematic diagram that manganese copper diverter is used in background of invention.
Fig. 2 is the structure chart of current transformer in background of invention.
Fig. 3 is the ammeter measurement loop schematic diagram that current transformer is used in background of invention.
Fig. 4 is the schematic diagram of sensing head in embodiment 1.
Fig. 5 is the embedded structural schematic diagram being fixed on pcb board of Fig. 4 sensing head.
Fig. 6 is the main view of 1 mutual inductor of embodiment.
Fig. 7-1 is the structure chart of monoblock type permalloy C-shaped magnetic yoke.
Fig. 7-2 is the structure chart of superposed type permalloy or microcrystallizing alloy C-shaped magnetic yoke.
Fig. 7-3 is the structure chart of superposed type silicon steel sheet C-shaped magnetic yoke.
Fig. 8 is the ammeter measurement loop schematic diagram using mutual inductor of the present invention.
Fig. 9 is the structural schematic diagram that embodiment 1 is applied to the measurement of three current loops.
Figure 10 is the explosive view of Fig. 9.
Figure 11 is the schematic diagram of sensing head in embodiment 2.
Figure 12 is the schematic diagram of sensing head in embodiment 3.
Figure 13 is the schematic diagram of sensing head in embodiment 4.
Figure 14 is the schematic diagram of sensing head in embodiment 5.
Below in conjunction with attached drawing, the present invention will be described in detail.
As shown in Fig. 6, Fig. 8, the present embodiment current transformer includes sensing head 1, flow guide bar 2 and C-shaped magnetic yoke 3, wherein
Sensing head 1, as shown in figure 4, the air core solenoid formed for one using conducting wire uniform winding, output end connection electricity
Flow sample circuit；
Flow guide bar 2, including the connected end of incoming cables linkage section 2-1 of sequence, induction section 2-2, leading-out terminal linkage section 2-3；Wherein
End of incoming cables linkage section 2-1 connection firewire end of incoming cables, leading-out terminal linkage section 2-3 connection firewire leading-out terminal, induction section 2-2 pass through described
C-shaped magnetic yoke 3 and correspondence be arranged in 1 side of sensing head, for after being powered between two planes up and down of 3 open end of C-shaped magnetic yoke,
It generates and current strength alternating magnetic field in a linear relationship；
C-shaped magnetic yoke 3, the sensing head 1 are inserted by the open end of C-shaped magnetic yoke 3, make C-shaped magnetic yoke 3 that the biography be completely covered
Feel head 1, induces electromotive force (specifically, generating after flow guide bar energization in 1 output end of sensing head using the alternating magnetic field
Changing magnetic field, to induce a voltage signal proportional to electric current no-load voltage ratio in sensing headIts induction coefficient M and coil factor kcoilWith magnet ring magnetic capacity kMagProduct it is related, indicate
For M=kcoil*kMag).In this example, line between 3 two ends (open end) of C-shaped magnetic yoke (C-shaped magnetic yoke open end up and down
The shortest route between two planes) it is parallel with the axis of air core solenoid, on the one hand constrain 1 leakage field of sensing head to external diffusion,
On the other hand interference of the external magnetic field to measurement circuit is prevented, measurement accuracy is improved；It is minimum in order to which external magnetic field interference to be reduced to
Limit, the resulting structure size that C-shaped magnetic yoke 3 is covered on sensing head 1 must reach 10mmx10mm or more.
In order to ensure realizing the separation between voltage and circuit measuring circuit, opening of the present embodiment in the C-shaped magnetic yoke 3
C-shaped insulating trip 4 identical with its opening direction is inserted in end, the sensing head 1 is inserted into the open end of C-shaped insulating trip 4, makes C-shaped
The sensing head 1 is completely covered in magnetic yoke 3 and C-shaped insulating trip 4；The flow guide bar 2 is from C-shaped magnetic yoke 3 and the enclosed sky of C-shaped insulating trip 4
It is passed through in chamber (positioned at the bottom of C-channel).
Preferably, the solenoid is fixed on the pcb board 5 where the current sampling circuit with embedded mode；Such as
Shown in Fig. 5, specifically, opening up a slot on pcb board 5, solenoid is placed in the slot, two output end is welded in
On pcb board 5, and it is connected with the current sampling circuit on pcb board.
The solenoidal internal diameter is 0.5-1.5mm, respectively corresponds direct access (such as: Ib=5A~10A, maximum electricity
Stream input 60A~200A) or through mutual inductor input (such as: rated current In=1A, maximum measurement electric current 2A~6A) etc. differences answer
Use demand；Winding the number of turns is 1-10 circle, depending on the thickness (thickness that solenoidal height is less than or equal to pcb board) of pcb board 5 and survey
Depending on the signal input range for measuring end.
In order to solve the Insulation Problems between flow guide bar 2 and air core solenoid, air core solenoid should use enameled wire coiling,
And the conducting wire on pcb board 5 needs to cover insulation green oil.
Preferably, the end of incoming cables linkage section 2-1, induction section 2-2, leading-out terminal linkage section 2-3 are linked in sequence into U-shaped,
Wherein induction section 2-2 passes through the C-shaped magnetic yoke 3, so that the C-shaped magnetic yoke 3 at least covering part incudes section 2-2, forms water conservancy diversion
Item 2 and C-shaped magnetic yoke 3 mutually hook the arrangement states drawn.
The material of the c-type magnetic yoke 3 can be according to the difference of measuring accuracy, selection permalloy, microcrystallizing alloy, or
Silicon steel sheet etc..The C-shaped magnetic yoke of three kinds of structure type is provided in the present embodiment, one kind is made of monoblock type permalloy, such as Fig. 7-1
It is shown, it is directly measured suitable for high current of the electric current between 5-200A, advantage is that measurement electric current is big, is not easy to be saturated, but linear
Degree is insufficient, needs to carry out segmented compensation；One kind is that permalloy or microcrystallizing alloy congruent manner (10 layers) are made, such as Fig. 7-2 institute
Show, the survey suitable for low current (0.3-10A) measurement that 0.5S or more high accuracy requires, the advantages of permalloy material laminate
It is wide to measure range, the disadvantage is that the linearity needs to compensate, and the advantages of microcrystallizing alloy lamination is that the measurement linearity is high, but range ability
It is slightly narrow, it is suitble to 0.2S grades of high-acruracy survey applications；One kind is that silicon steel sheet stack is box-like (10 layers), as shown in Fig. 7-3, is suitable for
The low current (1-10A) of 1.0 grades of medium error requirements measures, and cost is relatively low.
As shown in Figure 9, Figure 10, it when the present embodiment is applied to three current loop measurements, needs to be arranged three and is arranged side by side
C-shaped magnetic yoke 3 and a C-shaped insulating trip 4, each C-shaped magnetic yoke 3 be correspondingly arranged a flow guide bar 2, C-shaped insulating trip 4 is inserted into simultaneously
The open end of three C-shaped magnetic yokes 3.
The present embodiment by the way of the synchronous A/D sampling of voltage and current, what the practical frequency according to voltage signal converted
Then integration period of the period as air core solenoid carries out digital integration by MCU or DSP.
As shown in figure 11, the present embodiment is substantially the same manner as Example 1, and difference is: the sensing head 1 be directly print in
The spiral PCB type air core coil of plane quadrilateral where the current sampling circuit on pcb board 5, the number of turns are 3 circles, internal diameter
Din is 2mm, and outside diameter d out is 4.5mm.
As shown in figure 12, the present embodiment is substantially the same manner as Example 1, and difference is: the sensing head 1 be directly print in
The spiral PCB type air core coil of plane hexagon where the current sampling circuit on pcb board 5, the number of turns are 3 circles, internal diameter
Din is 2mm, and outside diameter d out is 4.5mm.
As shown in figure 13, the present embodiment is substantially the same manner as Example 1, and difference is: the sensing head 1 be directly print in
The spiral PCB type air core coil of planar octagonal where the current sampling circuit on pcb board 5, the number of turns are 3 circles, internal diameter
Din is 2mm, and outside diameter d out is 4.5mm.
As shown in figure 14, the present embodiment is substantially the same manner as Example 1, and difference is: the sensing head 1 be directly print in
Planar spiral-type PCB type air core coil where the current sampling circuit on pcb board 5, the number of turns are 3 circles, and internal diameter din is
2mm, outside diameter d out are 4.5mm.
The present embodiment is substantially the same manner as Example 2, and difference is: the 1 internal diameter din of sensing head is 1.5mm, outside diameter d out
The present embodiment is substantially the same manner as Example 3, and difference is: the 1 internal diameter din of sensing head is 1mm, and outside diameter d out is
The present embodiment is substantially the same manner as Example 4, and difference is: the 1 internal diameter din of sensing head is 0.6mm, outside diameter d out
The present embodiment is substantially the same manner as Example 5, and difference is: the 1 internal diameter din of sensing head is 1.5mm, outside diameter d out