Current Sense TransformersAs their name implies, current sense transformers “sense,” or detect, an electrical current (typically AC), accurately measure it based on Ohm’s Law, and/or “transform” it into more usable voltages for various instruments and devices.

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When only current sensing is needed, the primary winding is a conductor integral to the application that passes directly through the resistor. If the electrical current needs to be transformed, the current sense transformer may have both primary and secondary windings, or it may utilize a wire from the circuit to serve as the primary winding.

Current sense transformers “transform” AC electrical currents from larger-current values into smaller currents that are better suited for instruments, protective relays, and control circuits. This is achieved by developing a current in the secondary winding that is proportional to that of the primary. The isolation aspect of the transformer keeps the high voltage of the primary system separate from the instrument, safety circuit, or control circuit on the other side, thereby protecting them.

Current sense transformers must draw on some of the primary circuit’s energy to complete tasks, but the load is negligible. Plus, if the loss becomes a serious concern, the output voltage can be amplified as needed. Current sense transformers can also be used to trigger circuit events when the sensed current reaches a specified level. Large current transformers are an essential component in power systems as a whole and are often used in generating stations, electrical substations, and industrial and commercial electric power distribution.

Current Sense Transformers

Current Sense Transformers from Triad Magnetics

current-sense-cse186l-rt_4778Current sense transformers engineered and manufactured by Triad Magnetics are precise, easily implemented, and highly reliable even under harsh conditions. Since 2005, all of our standard products have met the requirements of RoHS 2015/863/EU.

Triad Magnetics’ ISO 9001:2015 certified U.S. Design Center offers complete custom current sense transformer design services. Our capabilities include rapid design, prototyping, and testing. In addition to creating a completely custom current sense transformer for your application, our engineers also have the capabilities to modify existing “off-the-shelf” current sense transformers to help you get the product you need.

Triad Magnetics is proud to offer five different standard product lines related to Current Sense Transformers, including the following:

CST206/CST306 Series High-Frequency Current Sense Transformers – The CST206/306 series is extremely reliable for operations across a frequency range of 20 kHz to 200 kHz. These models are specifically designed for detecting the current passing through a conductor in switching power supply applications. Constructed of materials UL-rated to 130 ºC (266 ºF), these transformers are also available with a center tap option. The rated primary current creates a temperature rise of approximately 40 °C (104 ºF), the maximum recommended terminating resistance is 1 ohm per turn, and the primary is inserted through-hole in the unit’s casting.

CSE5 Series High-Frequency Current Sense Transformers – The CSE5 series is specifically designed to monitor electrical currents at 250 kHz and higher. With a primary current rating of 10 amps, these surface-mounted transformers have an operating temperature range of -15 °C (5 ºF) to 105 °C (221 ºF). Common applications include AC current detection, output supply for control circuit, and switching power supply.

CSE Series Low-Frequency Current Sense Transformers – The CSE series is expertly designed to monitor electrical currents in low-frequency applications. These transformers are provided with a Recognized Component electrical insulation system (OBJY2), Class 130 (B), designated B3.

CST Series Low-Frequency Current Sense Transformers – The CST series operates effectively from 50 Hz to 60 Hz. These models are constructed with materials UL-rated to 130 ºC (266 ºF). The third pin on these transformers is for mechanical support only. Pin diameters are 0.8±0.1 mm, and pin lengths are 5±1 mm.

CST25 Series Current Sense Transformers – The CST25 series is ideal for monitoring currents in high-frequency applications such as switch-mode power supplies and LED lighting. These transformers feature a built-in sense winding, allowing for optimal ease of use, and are fully encapsulated to facilitate a high isolation of 4000 VAC between primary and secondary windings. Users can choose from four popular turn ratios: 1:50, 1:100, 1:200, and 1:500.

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Ready to learn more? Browse our online catalog of current sense transformers to see how we can help with your specific application needs. For more information about our custom current sense transformer capabilities and services, contact our team today!

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