IRV / ULV / IRM / ULM 600~1200 Series Metal Clad Resistors

What are the IRV / ULV / IRM / ULM 600~1200 Series Metal Clad Resistors?

The IRV, ULV, IRM, and ULM 600~1200 series represents the highest single-body power rating in the RMS standard metal clad resistor range — a family of high-power wire wound metal clad resistors spanning 600W to 1200W (on heatsink) that are engineered for sustained high-energy industrial applications including motor drives, regenerative braking, and high-power snubber networks.

The four model designations reflect two key variables: enclosure construction type and certification level. The IRV and IRM models are the standard series; the ULV and ULM are their UL-approved equivalents, sharing identical electrical characteristics and dimensions while additionally carrying UL certification for installations where regulatory compliance is mandatory. In terms of construction, IRV and ULV use cement moulding to encapsulate and protect the wire wound resistor element within the aluminium housing, while IRM and ULM use a metal cover — both approaches providing the strong, rugged mechanical protection and IP65-rated environmental sealing that demanding industrial and outdoor installations require.

All four variants share the same extruded aluminium housing, which functions as an integrated heatsink when the resistor body is bolted firmly to a chassis or external heatsink surface. For the higher-power 800W to 1200W models, a mid-point bracket is required to ensure full and even contact with the heatsink surface and achieve the rated power dissipation — a critical installation consideration when operating these models at or near full rated load. The recommended heatsink size for all models is Al 600 × 600 × 5mm.

Three termination configurations are available: tab terminals in parallel connection (Tab TP), tab terminals in serial connection (Tab TS), and flying leads — with the tab terminal configurations offering different resistance range coverage suited to low-resistance and higher-resistance applications respectively. Flying lead specifications are matched to the resistance and current requirements of each model, with standard wire for IRV/IRM variants and UL3512 AWG10 cable mandatory for ULV/ULM variants. Thermostat options (internal and discrete connection) are also available on request across the full range.

Both inductive and non-inductive winding configurations are available. The non-inductive option is essential for snubber and high-frequency switching applications where residual winding inductance would impair transient suppression performance. The resistance range spans 0.1Ω to 175Ω depending on model, winding type, and termination configuration, with tolerance options of ±1%, ±2%, ±5%, and ±10%.

Characterisation testing confirms reliable performance across short-time overload (10× rated power for 5 seconds), moisture resistance (40°C / 95% RH for 500 hours), thermal shock, vibration (10Hz–55Hz, 2 hours per axis), moisture load life, and extended full-power load life (1.5 hours on / 30 minutes off for 500 hours) — meeting the demands of continuous industrial duty cycles.

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: 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: LFH
Resistor type: Horizontal metal clad
Description: Industrial
Power Rating: 300W-2kW
Resistance (Ω): 0.1~7k
Tolerance (%): ±1, ±5, ±10
TCR (ppm/C):

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: 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):