Current Sense Transformers

Part Number	Description / PDF	Quantity
749251070 Würth Elektronik Midcom	CURR SENSE XFMR 1:70 10A SMD	435
749252060 Würth Elektronik Midcom	WE-CST CURRENT SENSE TRANSFORMER	1999
749252070 Würth Elektronik Midcom	WE-CST CURRENT SENSE TRANSFORMER	1996
749251050 Würth Elektronik Midcom	CURR SENSE XFMR 1:50 10A SMD	593
749252100 Würth Elektronik Midcom	WE-CST CURRENT SENSE TRANSFORMER	1995
749252040 Würth Elektronik Midcom	WE-CST CURRENT SENSE TRANSFORMER	2000
749252030 Würth Elektronik Midcom	WE-CST CURRENT SENSE TRANSFORMER	1994
750316796 Würth Elektronik Midcom	CURRENT SENSE TRANSFORMER	297
749251100 Würth Elektronik Midcom	CURR SENSE XFMR 1:100 10A SMD	75
749252050 Würth Elektronik Midcom	WE-CST CURRENT SENSE TRANSFORMER	1997
749252020 Würth Elektronik Midcom	WE-CST CURRENT SENSE TRANSFORMER	1990
749251040 Würth Elektronik Midcom	CURR SENSE XFMR 1:40 10A SMD	0
750316794 Würth Elektronik Midcom	CURRENT SENSE TRANSFORMER	225
749251125 Würth Elektronik Midcom	CURR SENSE XFMR 1:125 10A SMD	85
750316795 Würth Elektronik Midcom	CURRENT SENSE TRANSFORMER	0
750316793 Würth Elektronik Midcom	CURRENT SENSE TRANSFORMER	225
749252125 Würth Elektronik Midcom	WE-CST CURRENT SENSE TRANSFORMER	1990
749251060 Würth Elektronik Midcom	CURR SENSE XFMR 1:60 10A SMD	0
749251030 Würth Elektronik Midcom	CURR SENSE XFMR 1:30 10A SMD	0
749252150 Würth Elektronik Midcom	WE-CST CURRENT SENSE TRANSFORMER	1934

Current Sense Transformers

1. Overview

Current Sense Transformers (CSTs) are specialized electromagnetic devices designed to accurately detect and measure alternating current (AC) in electrical circuits. By converting primary current signals into proportional secondary currents or voltages, CSTs enable safe and reliable monitoring for control systems, energy management, and protection circuits. Their importance in modern technology spans power electronics, industrial automation, renewable energy systems, and smart grid infrastructure, where precise current measurement is critical for efficiency optimization and system safety.

2. Main Types and Functional Classification

Type	Functional Features	Application Examples
Open-Circuit Core CST	Low cost, wide current range, moderate accuracy	Smart meters, household appliances
Closed-Loop Core CST	High accuracy (0.1%~0.5%), low phase error	Motor drives, precision power supplies
Hall Effect Integration	DC/AC hybrid measurement, galvanic isolation	Electric vehicle BMS, energy storage systems
High-Frequency CST	Operates >100kHz, minimized core loss	Wireless charging systems, induction heating
Miniature Surface-Mount	Compact size, PCB-mountable	Consumer electronics, IoT devices

3. Structure and Components

Typical CST construction includes: - Magnetic Core: Made from ferrite, silicon steel, or nanocrystalline materials to ensure high permeability and low loss - Primary Winding: Single-turn or multi-turn conductor depending on current range - Secondary Winding: Multi-turn coil with precise turns ratio for signal scaling - Insulation System: Epoxy resin or plastic housing meeting UL/IEC dielectric standards - Termination: Screw terminals, PCB pins, or integrated connectors Advanced models incorporate shielding layers and temperature-compensated materials for enhanced stability.

4. Key Technical Specifications

Parameter	Typical Range	Significance
Current Ratio	100:1 to 5000:1	Determines scaling factor for measurement
Accuracy Class	0.1% to 1%	Critical for metering and control precision
Frequency Range	50Hz-1MHz	Dictates application suitability
Phase Shift	<1	Affects power factor calculation accuracy
Isolation Voltage	2.5kV-10kV	Ensures safety in high-voltage systems
Operating Temp.	-40 C to +125 C	Environmental reliability indicator

5. Application Fields

Major industries and equipment utilizing CSTs include:

Energy Sector: Smart grids, substation protection relays
Industrial Automation: Variable frequency drives, PLC systems
Renewable Energy: Solar inverters, wind turbine converters
Transportation: EV charging stations, traction control systems
Consumer Electronics: Smart home appliances, power banks

6. Leading Manufacturers and Products

Manufacturer	Representative Product	Key Features
ABB	ACS711	2kV isolation, 1% accuracy for EV charging
LEM	HASS 25-S	Open-loop sensor with 120A measurement range
TE Connectivity	CurrentSense 55512	Surface-mount design for PCB integration
Vacuumschmelze	DIN43858	High-frequency capability up to 500kHz
Allegro Micro	ACS37610	Digital output with I C interface

7. Selection Guidelines

Key considerations for CST selection:

Required current ratio and measurement range
Accuracy demands (metering vs. protection applications)
Environmental conditions (temperature, humidity, vibration)
Frequency characteristics of the target circuit
Space constraints and mounting requirements
Cost-performance balance for mass production

Example: For PV inverter applications, select a closed-loop core CST with >200kHz bandwidth and IP67 rating to ensure reliable operation under fluctuating environmental conditions.

8. Industry Trends

Emerging trends shaping CST development include:

Integration with digital interfaces (CAN, Modbus) for smart systems
Wide bandgap semiconductor compatibility (SiC/GaN circuits)
Nano-material core adoption for reduced size and weight
AI-enhanced error compensation algorithms
Increased adoption in EV infrastructure and energy storage systems

Market forecasts indicate 8.2% CAGR through 2030, driven by renewable energy integration and industrial IoT expansion.