### LA 55-TP Current Transducer Overview The **LA 55-TP** is a closed-loop (compensated) current transducer manufactured by LEM. It is designed for the electronic measurement of currents (DC, AC, pulsed, and mixed) with galvanic separation between the primary circuit and the secondary circuit. --- ### Technical Specifications | Feature | Specification | | :--- | :--- | | **Primary Nominal Current ($I_{pn}$)** | 50 A | | **Primary Current Measuring Range** | 0 to ±70 A | | **Secondary Nominal Current ($I_{sn}$)** | 50 mA | | **Conversion Ratio** | 1 : 1000 | | **Supply Voltage ($U_c$)** | ±12 V to ±15 V (±5%) | | **Accuracy** | ±0.65% of $I_{pn}$ (at +25°C) | | **Bandwidth (-1dB)** | DC to 200 kHz | | **Package Style** | PCB Mounting (Through-hole) | --- ### Key Internal Components & Technology 1. **Hall Effect Sensor:** The core sensing element located in the gap of the magnetic core. It detects the magnetic field generated by the primary current. 2. **Magnetic Core:** A high-permeability ring that concentrates the magnetic flux generated by the primary conductor. 3. **Compensation Coil (Secondary Winding):** A coil with 1000 turns. The electronics drive a current through this coil to create a magnetic field that exactly opposes (cancels) the primary field. 4. **Operational Amplifier/Driver:** An internal integrated circuit that processes the Hall voltage and controls the secondary current to maintain the "zero flux" condition. --- ### Pin Configuration and Connection The device typically features 3 or 4 pins for PCB integration: | Pin Designation | Description | | :--- | :--- | | **+** | Positive Supply Voltage (+12V to +15V) | | **-** | Negative Supply Voltage (-12V to -15V) | | **M** | Output (Measurement) Pin | | **Primary (Input)** | Through-hole for the primary conductor/wire | --- ### Application Circuit Principles To read the output, a burden resistor ($R_m$) must be connected between the **M** pin and the common ground (0V). The voltage across this resistor is proportional to the primary current. ```python # Calculating Output Voltage (Example) # If Primary Current (Ip) = 50A and Rm = 100 Ohms # Transformation ratio = 1:1000 Is = Ip / 1000 # Secondary Current = 0.05A (50mA) Vm = Is * Rm # Voltage = 0.05 * 100 = 5V ``` --- ### Advantages * **Excellent Linearity:** Due to the closed-loop technology. * **High Immunity:** Low sensitivity to external magnetic fields. * **Fast Response:** Response time is less than 1 µs, making it suitable for high-speed switching circuits.