Current sense transformers are designed to convert current up to values suitable for measurement and correspond the accuracy requirements for this type of transformers.
The specific feature of these transformers is obligate presence of load resistance in the secondary winding's circuit. The load resistance value is strictly regulated by the requirements for the transformation coefficient accuracy. Recommended load resistance nominal value for each current sense transformer produced by Epcos is specified in the manufacturer's documentation.
The fractional deviation of Rt from set value leads to changing of
transformation error and a degradation of transformer's measuring characteristics. A significant growth of load resistance creates a high voltage in the secondary winding of the transformer. The voltage value is sufficient for breakdown of insulation and functional loss of a transformer.
Formulas:
| Bmax= | Vsense,max⋅ δmax |
| ns. ⋅ Ae⋅ fOSC |
| Bmax - Maximum magnetic flux density in the ferrite core of the current sense transformer; |
| Vsense,max - Maximum output voltage of the measurement signal; |
| δmax - Maximum duty cycle; |
| nвтор - Number of turns of the secondary winding of the current sense transformer; |
| Ae - Effective magnetic area of the ferrite core; |
| fOSC -Operating frequency of the switching operator IC. |
| Typical values for Ae and Bmax are listed separately for each type of Epcos transformer in the technical data book. |
| RT= | Vsense,max⋅ ns |
| Iprim, max |
| RT - Resistance of burden resistor; |
| Vsense,max -Maximum output voltage of the measurement signal; |
| ns - Number of turns on the secondary side of the CT; |
| Iprim,max - Maximum primary current (peak current). |
Current sense transformer series
| B82801A (on the base of EE4.2 core) |
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Inductance Operating voltage Measured current |
33...1840 µH; 500 V (АС); 7 А. |
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| Lmin, µH | Turns ratio Nprim.:Nвтор. |
DC resistance Rmax, mΩ | Voltage-time product V ⋅ µs |
Recomm. RT | Ordering code | |
| primary | secondary | |||||
| 33 | 1 : 20 | 2.5 | 320 | 5.76 | 20 | B82801A0333A020 |
| 74 | 1 : 30 | 2.5 | 800 | 8.6 | 30 | B82801A0743A030 |
| 132 | 1 : 40 | 2.5 | 1300 | 11.5 | 40 | B82801A0134A040 |
| 205 | 1 : 50 | 2.5 | 2200 | 14.4 | 50 | B82801A0214A050 |
| 295 | 1 : 60 | 2.5 | 3600 | 17.3 | 60 | B82801A0304A060 |
| 400 | 1 : 70 | 2.5 | 4600 | 20.0 | 70 | B82801A0404A070 |
| 820 | 1 : 100 | 2.5 | 8700 | 28.8 | 100 | B82801A0824A100 |
| 1280 | 1 : 125 | 2.5 | 13000 | 36.0 | 125 | B82801A0135A125 |
| 1840 | 1 : 150 | 2.5 | 21000 | 43.2 | 150 | B82801A0185A150 |
| B82801B (on the base of EE5.0 core) |
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Inductance Operating voltage measured current |
80...8000 µH; 1000 V (АС); 20 А. |
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| Lmin, µH | Turns ratio Nprimary:Nsecondary |
DC resistance Rmax, mΩ | Voltage-time product V ⋅ µs |
Recommended RT | Ordering code | |
| Primary | Secondary | |||||
| 80 | 1 : 20 | 0.6 | 400 | 10.0 | 20 | B82801B0803A020 |
| 180 | 1 : 30 | 0.6 | 870 | 15.0 | 30 | B82801B0184A030 |
| 320 | 1 : 40 | 0.6 | 1140 | 20.0 | 40 | B82801B0324A040 |
| 500 | 1 : 50 | 0.6 | 1500 | 25.0 | 50 | B82801B0504A050 |
| 720 | 1 : 60 | 0.6 | 1980 | 30.0 | 60 | B82801B0724A060 |
| 980 | 1 : 70 | 0.6 | 3000 | 35.0 | 70 | B82801B0984A070 |
| 2000 | 1 : 100 | 0.6 | 5500 | 50.0 | 100 | B82801B0205A100 |
| 3000 | 1 : 125 | 0.6 | 6500 | 62.5 | 125 | B82801B0305A125 |
| 8000 | 1 : 200 | 0.6 | 33240 | 100.0 | 200 | B82801B0925A200 |
| B82801C (on the base of EE12.6 core) |
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Inductance Operating voltage Measured current |
1400...22400 µH; 1500 V (АС); 40 А. |
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| Lmin, µH | Turns ratio Nprimary.:Nsecondary. |
DC resistance Rmax, mΩ | Voltage-time product V ⋅ µs |
Recommended RT | Ordering code | |
| primary | secondary | |||||
| 1.4 | 1 : 50 | 0.28 | 400 | 124 | 50 | B82801C0145A050 |
| 5.6 | 1 : 100 | 0.28 | 1000 | 248 | 100 | B82801C0565A100 |
| 12.6 | 1 : 150 | 0.28 | 2200 | 372 | 150 | B82801C1265A150 |
| 22.4 | 1 : 200 | 0.28 | 2900 | 496 | 200 | B82801C2245A200 |
Replacement of Transformer Series B82801A0* with New Series B82801A1*
To streamline the product range the following types from the B82801A0* series of EPCOS SMT current sense transformers are being withdrawn.
- EE4.2 SMD Current Sense Transformer series B82801A0* produced by TDK (Epcos) must be withdrawn. As a replacement, the company is introducing the new series B82801A1*
- The new series B82801A1* is pin-compatible with the B82801A0* series and the majority of the electrical characteristics are unchanged. Details about mechanical and electrical differences are explained in the TDK (Epcos) informational newsletter.
- Samples of the new B82801A1* series are available. The part numbers are: B82801A1214A050 B82801A1824A100 B82801A1185A150 have already been released for mass production. The remaining types in the B82801A1* series are expected to be released for production in February / March of 2019.
Additional information
The selection of current sense transformers produced by EPCOS according to parameters
In order to choose required current sense transformers produced by EPCOS one can use
the program at TDK-EPCOS website
Stock status
To know the actual prices , availability at stock one can use our online-shop.
