Embodiment
Mark in the accompanying drawing: in the accompanying drawing 1: Z
1---primary impedance Z
1(comprise winding resistance R one time
1With a winding leakage reactance X
1), Z
2---the secondary winding impedance Z
2(comprise winding resistance R one time
2With a winding leakage reactance X
2), Z
0---the excitation winding impedance Z
0(comprise the excitation winding resistance R
0With excitation winding induction reactance X
0), Z
B---secondary load, U
1---transformer primary side voltage, U
2---Circuit Fault on Secondary Transformer voltage, I
0---exciting current, I
2---load current;
In the accompanying drawing 2: A, N---high-pressure side winding terminal, a, n---low-pressure side winding terminal, a ', n '---voltage transformer function terminal,
---the no-load error compensating unit,
---load error compensating unit, U
2'---the voltage transformer output voltage;
In the accompanying drawing 3: T---the low pressure miniature transformer;
In the accompanying drawing 4: Z
b---low pressure miniature transformer secondary capacitive reactances;
In the accompanying drawing 5: T '---the low pressure miniature transformer of two secondary winding;
In the accompanying drawing 6: CT
B---compensation Current Transformer, Z
F---the secondary load of compensation Current Transformer;
In the accompanying drawing 7: CT---current transformer, K
1, K
2---CT secondary terminal;
In the accompanying drawing 8:
A, B, C---three-phase transformer high-pressure side winding terminal
A, b, c, n---three-phase transformer low-pressure side winding terminal
A ', b ', c '---three-phase transformer voltage transformer function terminal
CT
a, CT
b, CT
c---threephase current transformer
CT
Ba, CT
Bb, CT
Bc---three-phase compensation Current Transformer
T
a, T
b, T
c---the three-phase low pressure miniature transformer of two secondary winding
Z
Fa, Z
Fb, Z
Fb---the secondary load of three-phase compensation Current Transformer
Z
Ba, Z
Bb, Z
Bb---three-phase low pressure miniature transformer secondary impedance
K
A1, K
A2, K
B1, K
B2, K
C1, K
C2---threephase current transformer secondary terminal.
Below in conjunction with accompanying drawing inventive embodiments is described further:
With reference to accompanying drawing 1, shown in 2, causing the main cause of the proportionate relationship generation deviation (error) between conventional transformer secondary side voltage and the primary side voltage is exciting current I
0At primary impedance Z
1The error ε of last generation
0(be referred to as no-load error, ε
0=I
0Z
1), and the secondary load electric current I
2At primary impedance Z
1With the secondary winding impedance Z
2The load error ε of last generation
L, ε
L=I
2(Z
1+ Z
2), if take no-load error ε
0Compensation and load error ε
LCompensation way, as shown in Figure 2,
With
Be no-load error ε
0Compensation compensating unit and load error ε
LCompensating unit.The physical circuit kind of compensating unit is a lot, can improve the accurate level of the proportionate relationship between conventional transformer secondary side voltage and the primary side voltage.Among the utility model embodiment: the A-N terminal, represent transformer first side winding terminal, and the relation of the voltage ratio between the secondary side terminal a-n (U
1/ U
2), there is no-load error ε
0With load ε
LThat is:
(U
2-U
1)/U
1=1+ε
0+ε
L
Seal in " ε in secondary side voltage terminal high-pressure side
0" and " ε
L" compensating unit compensates, and can eliminate no-load error ε
0With load ε
LEffect, make that the voltage ratio between A-N terminal and a '-n ' terminal concerns that error is less, that is: (U
2'-U
1)/U
1≈ 1.
A '-n ' terminal is as the voltage transformer function terminal use of transformer.
1) the no-load error ε of voltage ratio relation
0Compensation
No-load error ε
0Show that by Fig. 3 method compensates, the low pressure miniature transformer T of parallel connection, the difference in magnitude when secondary output terminals is used to compensate zero load.
Except carrying out the compensation of no-load error, also has the voltage transformer error compensation way of a lot of other kinds with this mode of miniature transformer T.If no-load error ε
0Also there is phase difference, can be at the secondary side parallel impedance Z of low pressure miniature transformer T
b, carry out phase compensation, as shown in Figure 4.The secondary winding of the shared low pressure miniature transformer of difference in magnitude and phase difference T, and the number of turn of secondary winding can design according to compensation rate.Usually the power consumption of low pressure miniature transformer T is in the mW level, secondary side parallel connection capacitive reactances Z
b
No-load error ε
0Also can compensate by method shown in Figure 5, low pressure miniature transformer T has 2 secondary winding, increases an independently phase compensation terminal, like this than the be more convenient for impedance Z of selecting phase adjusted to use of Fig. 4
b, the capacitor that can need compensate by phase difference calculating earlier, ratio difference is regulated separately with another secondary winding.
2) load error ε
LCompensation
Fig. 6 is the load error compensation way.Series compensation Current Transformer CT before secondary voltage terminal a-n
BSecondary load Z
FBecause Z
FOn voltage be directly proportional with the secondary load electric current, can compensate because of secondary load and be increased in Z among Fig. 1
1+ Z
2On pressure drop.In the design, compensation Current Transformer CT
BThe design of secondary current should be far longer than the output current of terminal a-n, to guarantee that measurement mechanism, metering device insert the load shunting that produces and need; Z
FWith Z
1+ Z
2Be directly proportional, and Z
FWith compensation Current Transformer CT
BSecondary current long-pending, equal Z
1+ Z
2Long-pending with the transformer secondary load current; Compensation Current Transformer CT
BSecondary winding and a winding reversed polarity.
3) ERROR CONTROL of composition error characteristic compensation and compensating element,
With no-load error ε
0Compensation and load error ε
LCompensation combine, just constituted the composition error characteristic compensation, see accompanying drawing 7.
General general distribution transformer, at full capacity and under unloaded two kinds of situation, primary voltage and secondary voltage only than variable quantity about 5% to 8%, guarantee that voltage transformer lead-out terminal a '-n ' satisfies 0.2 grade of level requirement, no-load error ε
0Compensating element, T and load error ε
LCompensating element, CT
BERROR CONTROL get final product at 1 grade or 2 grades.For example, when transformer had 5% deviation, the error range of compensation rate was: 100%-5%+5% (1 ± 2%)=95%+5% ± 0.1%=100% ± 0.1%, satisfy 0.2% level requirement; For example, 8% deviation, the error of compensation rate are 100%-8%+8% (1 ± 2%)=92%+8% ± 0.16%=100% ± 0.16%,, also satisfy 0.2% level requirement.
4) has the single-phase transformer overall structure of instrument transformer function
Fig. 7 in fact also is the single-phase transformer overall structure circuit diagram with instrument transformer function, increases a current mutual inductor coil CT.Secondary terminal a '-n ' and k
1-k
2, constituted the secondary terminal of the instrument transformer function of transformer.CT can design by the conventional current mutual inductor coil, and increases number of ampere turns of CT also than being easier at low-voltage terminal, guarantees that CT satisfies accuracy requirement.When low-power consumption requires, CT and CT
BCan combine together.
5) three-phase transformer part
Fig. 8 is the three-phase transformer overall structure figure with instrument transformer function.Circuit Fault on Secondary Transformer neutral point and voltage transformer neutral point be " n " terminal altogether.Compensation way is a benchmark with the phase voltage still, and during use, a '-n terminal can be combined into corresponding and terminal: an a '-b ' A-B with b '-n terminal.Current Transformer Secondary terminal K
A1-K
A2, K
B1-K
B2, K
C1-K
C2Only corresponding to the electric current of transformer secondary output a, b, c.
Be example with a 10KV/50KVA single-phase transformer below: transformer voltage ratio is 10KV/380V, short-circuit impedance 6%, no-load loss 2%.According to above-mentioned parameter, the exciting current 100mA under the rated primary voltage, the rated primary voltage load current 5A under at full capacity, the load current about 132A of rated secondary voltage under at full capacity, the short-circuit impedance of converting secondary side is 0.173 Ω.When the actual product impedance is perception, can adopt capacitor, reach emotional resistance compensation purpose through secondary coil reverse (180 ° of phase shifts).
The no-load error compensation uses low pressure miniature transformer T to be annular core, and core section is long-pending can select 6cm
2, the close 0.8T of magnetic, adopting line directly is enamelled wire coiling 3210 circles of 0.18mm, and its secondary winding selection wire directly is the enamelled wire coiling of 0.56mm, and the coiling number of turn is confirmed according to the actual no-load error measured value of transformer.When no-load error+2%, when the secondary line number of turn was selected 3210 * 0.02=64 circle, the phase difference compensation winding can differentially-wound group parameter on year-on-year basis equally be selected, and condenser capacity is selected to confirm according to the phase difference degrees of offset.
Compensation Current Transformer CT
BPress the 300AT design, annular core, no-load voltage ratio is got 150A/1A and is considered that its secondary load resistance is by 0.173 * 150=26 Ω, and core section amasss 6cm
2, it directly is the enamelled wire coiling of 1mm that secondary winding adopts line, 0.5 grade.