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# SPICE Model of Current Transformer

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SPICE Model of Current Transformer

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### SPICE Model of Current Transformer

1. 1. Summery　: current transformer <br />A current transformer (CT) <br />usually used for measurement of currents (especially large values)<br />when large values of current are expected, a CT reduces current proportional to the current in the circuit (primary current).<br />Modeling Concept:<br />Use the secondary side of a ‘voltage’ transformer model as a the current sensor then transform by 1/n to another side.<br />All Rights Reserved Copyright (C) Bee Technologies Corporation 2011<br />1<br />1 : n<br />Isensed<br />Isensed/n<br />
2. 2. <ul><li>Modeling Concept: Use the secondary side of a ‘voltage’ transformer model as a the current sensor then transform by 1/n to another side.</li></ul>The current transformer model (primitive)<br />CT Model (Primitive)<br />All Rights Reserved Copyright (C) Bee Technologies Corporation 2011<br />2<br />Isensed<br />Isensed/n<br />(1 : n)<br />+<br />+<br />VOUT<br />VOUT/n<br /><br /><br />
3. 3. <ul><li>Example: Vpower=10kV, Rload=10 , Rburden=10 , and n=1000</li></ul>The current transformer model and its application (Isensed=1kA, VOUT=10V)<br />CT Model and Application<br />All Rights Reserved Copyright (C) Bee Technologies Corporation 2011<br />3<br />Isensed=1kA<br />(1 : 1000)<br />Isensed/n=1A<br />VOUT=10V<br />+<br />+<br />VOUT/n=10mV<br /><br /><br />
4. 4. CT Model and Application<br />The current transformer model and its application (Isensed=1kA, VOUT=10V)<br />All Rights Reserved Copyright (C) Bee Technologies Corporation 2011<br />4<br />Isensed=1kA(peak)<br />VOUT/n=10mV(peak)<br />Isensed/n=1A(peak)<br />VOUT=10V(peak)<br />
5. 5. <ul><li>Lm (CT equivalent inductive magnetization), Rp, and Cp can be measured and added to the model.
6. 6. This will limit the frequency range of the CT</li></ul>CT Model + Lm<br />All Rights Reserved Copyright (C) Bee Technologies Corporation 2011<br />5<br />Measured and Added to the model<br />
7. 7. CT Model Frequency Range<br /><ul><li>Lm and Cp limit the frequency range of the current transformer.</li></ul>All Rights Reserved Copyright (C) Bee Technologies Corporation 2011<br />6<br />FREQUENCY RANGE<br />
8. 8. <ul><li>The leakage inductance and wire resistance of the secondary side can be measured and added to the model for better simulation result</li></ul>CT Model + Lleakage + Rwire<br />All Rights Reserved Copyright (C) Bee Technologies Corporation 2011<br />7<br />Measured and Added to the model<br />
9. 9. Device Modeling<br />Input the current transformer spec: 1:n<br />Measure and input Lm, Rp, and Cp<br />Measure and input Llk, Rlk, and Clk<br />All Rights Reserved Copyright (C) Bee Technologies Corporation 2011<br />8<br />