ULV 300 Resistor Specs: Detailed 210W Free-Air FL=1000
Measured across standard test conditions, the ULV 300 resistor delivers up to 300 W on a heatsink and approximately 210 W in free air (FL=1000). For thermal-critical applications—braking, load-dumping, energy recovery—understanding the 210W free-air limit and the FL=1000 test condition is essential to avoid premature failure. The following data-driven overview and procedures give engineers the tests, derating math, and mounting checks needed for reliable integration.
1 — Product overview & key specifications
1.1 Electrical specification breakdown
| Parameter | Typical Value / Notes |
|---|---|
| Resistance values | 0.1 Ω – 10 kΩ |
| Tolerance | ±1% / ±5% |
| Rated power | 300 W (Heatsink) / ~210 W (Free-air FL=1000) |
| Temp. coefficient | ±50–250 ppm/°C |
| Max continuous current | P=I²R (Observe Vmax) |
| Test conditions | Ambient 25°C, FL=1000 standard |
2 — Thermal performance & derating
2.1 Free-air vs heatsink ratings (FL=1000)
FL=1000 indicates the standard free-air test condition. In practice, a heatsink or forced airflow raises allowable dissipation. Designers must map their actual convection (air speed, orientation) to the FL=1000 baseline before relying on published ratings.
2.2 Derating curves: ambient and altitude
| Ambient (°C) | % of Rated Power |
|---|---|
| 25°C | 100% (210W) |
| 50°C | 80% (168W) |
| 75°C | 60% (126W) |
| 100°C | 40% (84W) |
3 — Electrical behavior and performance under load
Transient Handling: Pulsed energy capability is driven by element thermal mass. For pulse trains, convert energy to average power: P_avg = E_pulse × pulses_per_second. Example: 500 W for 1 s every 10 s yields 50 W average, well within the 210W free-air limit.
4 — Mounting & installation best practices
- Heatsinking: To reach 300W, use a dedicated machined plate with thermal interface material (TIM).
- Torque: Apply 8–10 N·m for M6 fasteners in a cross pattern to ensure uniform contact.
- Clearance: Maintain minimum creepage distances per system voltage to avoid dielectric breakdown.
5 — Test procedures & validation
Lab validation should reproduce FL=1000 conditions. Place thermocouples on the element and log temperature rise until steady state. Acceptance criteria: temperature rise must remain within datasheet limits after 30 minutes of continuous load at 210W.
Frequently Asked Questions
What exactly does FL=1000 mean for the ULV 300 resistor?
FL=1000 denotes the standardized free-air test/load condition used to rate the resistor’s free-air power. It defines convection and thermal boundary conditions in the test. Engineers should reproduce equivalent convection in lab validation to ensure the ~210W number applies.
How do I convert pulse energy in joules to average watts?
Use P_avg = E_pulse / T (where T is the period). This average power must be compared to the derated continuous power at your specific ambient temperature to confirm safe operation.
Is heatsink mounting always required to exceed 210W?
Yes. For sustained continuous dissipation above 210W, a heatsink or forced-air arrangement is the only reliable path to approach the 300W maximum rating without exceeding the element's thermal ceiling.
How does altitude affect the ULV 300 power rating?
Higher altitudes have lower air density, reducing convection efficiency. A typical derating of 10% per 1000m above 2000m altitude should be applied to the free-air rating.
Disclaimer: Specifications are subject to change. Always consult the latest manufacturer datasheet before final PCB layout.
