Shunt

I. Electronics / Power Industry (Most Common)

1. Core Definition and Principle

• Nature: A low-resistance, high-precision power resistor (in milliohm/microohm scale).
• Principle: Connected in series in the measured circuit. A high current produces a millivolt-level voltage drop (U=I×R), and the current is calculated indirectly by measuring the voltage.
• Typical specifications: Rated voltage drop is mostly 75mV/100mV. For example, 100A/75mV corresponds to a resistance of 0.75mΩ.

2. Main Applications

• High-current measurement: Used with millivoltmeters / multimeters to measure high DC current (from dozens to tens of thousands of amperes).
• Range extension: Connected in parallel with a low-range ammeter to shunt most of the current, allowing only a small portion to pass through the meter.
• Current sampling: Used for current monitoring and protection in BMS, motor control, power supplies, charging piles, and energy storage systems.

3. Key Parameters and Selection

• Rated current: Ranges from 5A to 15kA.
• Rated voltage drop: 60mV, 75mV, 100mV, 150mV, etc.
• Accuracy: 0.1%, 0.2%, 0.5%, 1%, etc.
• Material: Usually manganin alloy (low temperature coefficient, good stability).
• Heat dissipation: High-current applications require good heat dissipation to prevent accuracy loss due to temperature rise.

4. Advantages and Disadvantages

• Advantages: Simple structure, low cost, high DC accuracy, suitable for high currents.
• Disadvantages: Voltage drop loss, heat generation, non-isolated, and accuracy affected by reactance at high frequencies.

II. “Shunt” in Other Fields

1. Network Shunt (Traffic Replication / Load Balancing)

2. Hydraulic / Pneumatic Shunt

3. Faucet Shunt (Household)

III. Usage Notes

• Must be connected in series in the measured circuit.
• Rated current should be higher than the actual maximum current (20% margin recommended).
• Secure wiring to reduce contact resistance; four-wire connection is recommended for high-precision measurement.
• Pay attention to heat dissipation to avoid overheating.
• Mainly used for DC or low-frequency AC; use with caution in high-frequency applications.