IRM/ULM 1600W to 2800W Series Metal Clad Resistors

What are the IRM/ULM 1600W to 2800W Series Metal Clad Resistors?

The IRM/ULM 1600–2800 is a high-power aluminium-housed wire-wound metal clad resistor engineered for demanding industrial applications where robust construction, wide thermal tolerance, and reliable overload performance are essential. Available in four frame sizes, the series covers a continuous power range of 570W to 750W in free air, with a resistance range of 0.3Ω to 144Ω (inductive) or 0.3Ω to 37Ω in non-inductive configuration — making it well suited to motor drive braking choppers, snubber circuits, and industrial power source applications.

The extruded aluminium housing provides both mechanical rigidity and effective passive heatsinking when chassis-mounted, dissipating the sustained thermal loads generated in continuous braking and dump-load duty. An operating temperature range of –55°C to +200°C accommodates the extremes of industrial environments, from cold-start conditions to undercabinet heat soak in enclosed drive enclosures.

Three tolerance classes — ±1%, ±5%, and ±10% — are available, with a temperature coefficient not exceeding ±260ppm/°C. The IRM series offers flexible dielectric strength options (AC 1500V, 2500V, 3500V, or 4500V for 1 minute), while the ULM series carries UL certification with a standard dielectric strength of AC 2200V for 1 minute (system input voltage max. 600V), with higher dielectric options also available. Insulation resistance is guaranteed at 20MΩ minimum. Both inductive and non-inductive winding configurations are offered, with flying lead options in UL3512 AWG10 and AWG14. A thermal protector option is also available for over-temperature shutdown in enclosed or high-duty-cycle installations.

The IRM/ULM has been verified across a comprehensive qualification test programme, including vibration (10Hz–55Hz, 2 hours per axis), short-time overload at 10× rated power for 5 seconds, moisture resistance at 40°C/RH95% for 500 hours, thermal shock cycling, and 500-hour load life testing — confirming the structural and electrical integrity required for continuous industrial service.

Braking & snubber application note: In variable-speed drive and inverter systems, the IRM/ULM is typically connected across the DC bus via a braking chopper transistor. During motor deceleration or overhauling load conditions, regenerative energy raises the DC bus voltage above the regulation threshold, causing the chopper to switch the braking resistor into circuit. The IRM/ULM absorbs this energy as heat, clamping the DC bus and protecting the drive from overvoltage faults. Its high short-time overload capability — 10× rated power for 5 seconds — is specifically sized to handle these repetitive pulse loads without degradation.

Model: IRM, ULM
Resistor type: Metal clad resistor
Description: UL/CE, aluminum housed, chassis mounted
Power Rating: 1.6kW-2.8kW
Resistance (Ω): 0.3~144
Tolerance (%): ±1, ±5, ±10
TCR (ppm/C): 260 Max.

Model: IRH, IRV, ULH, ULV
Resistor type: Metal clad resistor
Description: UL/CE, aluminum housed, chassis mounted
Power Rating: 60W~500W
Resistance (Ω): 0.1~6.8k
Tolerance (%): ±0.5, ±1, ±2, ±5, ±10
TCR (ppm/C): 260 Max.

Model: IRVA
Resistor type: Metal clad resistor
Description: Chassis mounted assembly
Power Rating: 300W-450W
Resistance (Ω): 30~15k
Tolerance (%): ±1, ±2, ±5, ±10
TCR (ppm/C): 260 Max.

Model: IRV, ULV, IRM, ULM600-1200
Resistor type: Metal clad resistor
Description: UL/CE, aluminum housed, chassis mounted
Power Rating: 600W-1.2kW
Resistance (Ω): 0.1~175
Tolerance (%): ±1, ±2, ±5, ±10
TCR (ppm/C): 260 Max.

Model: SFH/SFV
Resistor type: Metal clad resistor
Description: Industrial
Power Rating: 60W~200W
Resistance (Ω): 0.1~2.2k
Tolerance (%): ±1, ±5, ±10
TCR (ppm/C):