Shunt power dissipation & temperature rise
Shunt resistors dissipate heat due to I²R losses. Understanding power dissipation is essential for stable measurement, low drift, and safe operation.
Key formulas
- R = V / I
- P = I² · R
- P = V · I (same result if V is the shunt drop)
Why power matters
- Higher power → higher temperature rise → higher drift (TCR effect).
- High temperature can affect nearby components and insulation.
- Thermal gradients reduce repeatability if sensing points are not Kelvin.
Continuous vs duty cycle
If your system runs peaks rather than continuous current, duty cycle is critical. A shunt can handle higher peak current for short durations if average power is managed.
- Define peak current and duration (ms / s).
- Define repetition (how often).
- Consider airflow and mounting mass as thermal buffers.
Thermal design notes
- Mounting: busbar mounting can spread heat, reduce hotspot temperature.
- Airflow: forced airflow dramatically improves thermal margin.
- Derating: use derating at high ambient temperature.
- Sense wiring: use Kelvin taps to reduce errors from temperature gradients.
Calculate your dissipation
Use our calculator to estimate resistance and I²R power dissipation.
Open calculator Request RFQFAQ
Is a 300W shunt always too hot?
Not necessarily. Temperature rise depends on design, mounting, airflow and duty cycle.
Many high-current shunts are designed to dissipate hundreds of watts when mounted correctly.
Does temperature rise affect accuracy?
Yes. Resistance changes with temperature (TCR). Higher temperature rise can increase drift
unless the shunt and sensing method (Kelvin) are designed for stable measurement.