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Product Overview
Electromagnetic induction powers a CT, which has two windings: a primary winding with a few turns linked in series with the high-current circuit and a secondary winding with numerous turns connected to safety or measurement devices. The primary winding receives a high current while the secondary winding, which is usually tuned to 5A or 1A for most industrial applications, receives a low current. This proportionality—also referred to as the transformation ratio—allows for accurate current monitoring while shielding workers and equipment from potentially dangerous voltages.
CTs require sufficient insulation to maintain high voltage between windings, sufficient linearity to minimize measurement error, and high precision for energy metering. When using a CT, the secondary winding should never be open circuit. This is because an open circuit might result in extremely high voltages that could harm electrical equipment. In conclusion, since they enable more precise current monitoring and improved problem avoidance, current transformers are crucial to ensuring the reliability, efficiency, and safety of modern electrical systems.
CTs require sufficient insulation to maintain high voltage between windings, sufficient linearity to minimize measurement error, and high precision for energy metering. When using a CT, the secondary winding should never be open circuit. This is because an open circuit might result in extremely high voltages that could harm electrical equipment. In conclusion, since they enable more precise current monitoring and improved problem avoidance, current transformers are crucial to ensuring the reliability, efficiency, and safety of modern electrical systems.
- ⚡ Electromagnetic Induction: Powers the CT with primary and secondary windings for safe current transformation.
- 🔒 High Insulation: Maintains safe high voltage separation between windings at all times.
- 📏 High Precision: Ensures accurate energy metering with superior linearity and minimal measurement error.
- ⚠️ Safety Warning: Secondary winding must never be open circuit to prevent dangerously high voltages.
Technical Parameters
| Type | Rated Current (A) | Rated Burden (VA) | Class | Rated Voltage (V) | Rated Frequency (Hz) |
|---|---|---|---|---|---|
| SF45/14 | 30/5A ~ 100/5A | 1.5 ~ 2.5 | 1.0 ~ 0.5 | 720 | 50/60 |
| SF62/20 | 30/5A ~ 200/5A | 1.5 ~ 2.5 | 3.0 ~ 0.5 | 720 | 50/60 |
| SF62/30 | 100/5A ~ 400/5A | 1.5 ~ 5 | 1.0 ~ 0.5 | 720 | 50/60 |
| SF62/40 | 200/5A ~ 600/5A | 5 ~ 10 | 1.0 ~ 0.5 | 720 | 50/60 |
| SF74/40 | 150/5A ~ 600/5A | 2.5 ~ 20 | 1.0 ~ 0.5 | 720 | 50/60 |
| SF74/50 | 250/5A ~ 1000/5A | 5 ~ 20 | 1.0 ~ 0.5 | 720 | 50/60 |
| SF86/60 | 250/5A ~ 1200/5A | 5 ~ 30 | 1.0 ~ 0.5 | 720 | 50/60 |
| SF104/80 | 600/5A ~ 2000/5A | 5 ~ 45 | 1.0 ~ 0.5 | 720 | 50/60 |
| SF140/100 | 1000/5A ~ 3200/5A | 5 ~ 50 | 1.0 ~ 0.5 | 720 | 50/60 |
Outline Drawing (unit: mm)
| Type | A | B | C | D | E | F | G | H | I | J | K | L | M | N | O |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| SF45/14 | 65 | 30 | — | 30 | 53 | 68 | 15 | — | — | — | — | — | 45 | — | — |
| SF62/20 | 78 | 36 | 6.6 | 36 | 55 | 71 | 30.1 | 30.1 | 11 | 23 | 44 | 21 | 62 | 21 | 26 |
| SF62/30 | 78 | 47 | 6.6 | 35 | 55 | 71 | 31 | 31 | 16 | 31 | 44 | 31 | 62 | 21 | 26 |
| SF62/40 | 78 | 47 | 6.6 | 35 | 55 | 71 | 33 | 33 | 11 | 31 | 47 | 41 | 74 | 21 | 31 |
| SF74/40 | 98 | 61 | 6.6 | 45 | 67 | 81 | 41 | 41 | 31 | 41 | 47 | 41 | 74 | 21 | 31 |
| SF74/50 | 98 | 61 | 6.6 | 45 | 67 | 81 | 51 | 51 | 21 | 51 | 68 | 51 | 86 | 31 | 44 |
| SF86/60 | 110 | 56 | 6.6 | 40 | 62 | 76 | 65 | 65 | 31 | 61 | 86 | 61 | 104 | 31 | 56 |
| SF104/80 | 126 | 56 | 6.6 | 40 | 62 | 76 | — | — | — | — | — | 81 | — | — | — |
Frequently Asked Questions (FAQ)
Q
What is the working principle of a current transformer (CT)?
A current transformer operates on the principle of electromagnetic induction. It consists of a primary winding connected in series with the high-current circuit and a secondary winding connected to measurement or protection devices. The high current in the primary induces a proportionally reduced current in the secondary, enabling safe and accurate current monitoring.
Q
What is the standard secondary output current for industrial CTs?
For most industrial applications, the secondary winding of a current transformer is standardized to either 5A or 1A. This allows safe interfacing with metering instruments and protection relays regardless of the primary current magnitude.
Q
Why should the secondary winding of a CT never be left open circuit?
If the secondary winding is left open circuit while current flows through the primary, the transformer core becomes saturated and generates an extremely high voltage across the secondary terminals. This can be dangerous to personnel and can permanently damage the transformer and connected equipment. Always ensure the secondary circuit is closed or short-circuited before disconnecting any instruments.
Q
What accuracy classes are available for these current transformers?
The current transformers in this series are available in accuracy classes ranging from Class 0.5 to Class 3.0, depending on the model. Class 0.5 is suitable for precision energy metering, while higher classes are typically used for general measurement and protection applications.
Q
What rated voltage and frequency do these CTs support?
All models in this series support a rated voltage of 720V and are compatible with both 50Hz and 60Hz rated frequencies, making them suitable for use in a wide range of global electrical systems and industrial environments.
Q
How do I select the correct CT model for my application?
To select the correct CT model, consider the primary current range of your circuit, the required accuracy class, the rated burden (VA) of your connected instruments, and the physical window size needed to accommodate your bus bar or cable. Refer to the Technical Parameters table above to match your requirements with the appropriate model (e.g., SF45/14 for lower currents up to 100/5A, or SF140/100 for high-current applications up to 3200/5A).