EWS Series Edge Wound Resistors

What are the EWS Series Edge Wound Resistors?

The EWS Series is a range of high-power edge wound resistors designed for demanding industrial applications where large amounts of energy must be dissipated reliably and continuously. Unlike conventional axial wire wound resistors where resistance wire is wound flat against a core, edge wound construction orients the resistive ribbon on its edge as it spirals around the ceramic former. This geometry substantially increases the exposed surface area of the resistive element compared to the core footprint, allowing significantly more heat to be transferred to the surrounding air per unit of physical length. The result is a resistor capable of handling 400W to 1600W of continuous power dissipation in a form factor that remains practical for panel and enclosure mounting.

The resistance range of the EWS Series spans 0.02Ω to 1Ω, reflecting the series’ primary role in braking and motor control circuits where very low impedance loads are required to absorb high currents at relatively low voltages. The low resistance values combined with high power ratings give the EWS Series the ability to handle the large instantaneous currents that arise when a variable frequency drive decelerates a heavy motor load, or when a servo system performs rapid repetitive positioning cycles. Tolerance options of ±5% and ±10% are available across the range, with a temperature coefficient of resistance (TCR) of ±800ppm/°C maximum — appropriate for power dissipation service where precise absolute resistance is less critical than thermal stability and mechanical robustness.

The ceramic former provides both electrical insulation and dimensional stability at the elevated operating temperatures characteristic of sustained high-power duty. The open construction of the edge wound element allows natural convection to remove heat from the resistor body without requiring direct contact with a heatsink, simplifying mechanical installation compared to heatsinkable flat-pack types. This makes the EWS Series straightforward to mount in ventilated control cabinets and drive enclosures, with the element geometry itself acting as the primary thermal management structure.

The EWS Series sits at the single-unit end of RARA’s edge wound product family. For applications requiring higher total power dissipation beyond 1600W, RARA’s EW series provides pre-assembled edge wound resistor assemblies rated from 3kW up to 12kW, where multiple elements are combined into a single structural unit. The EWS and EW series together cover the full range of edge wound braking resistor requirements from individual drive axes up to large multi-motor industrial installations.

Model: EWS
Resistor type: Wire wound
Description: Edge wound
Power Rating: 400W~1600W
Resistance (Ω): 0.02~1
Tolerance (%): ±5, ±10
TCR (ppm/C): 800 max.

Model: K
Resistor type: Wire wound
Description: Non-flammable
Power Rating: 15W-2000W
Resistance (Ω): 1~1200k
Tolerance (%): ±5, ±10
TCR (ppm/C): 200 max.

Model: EW
Resistor type: Wire wound
Description: Edge wound assembly
Power Rating: 3kW~12kW
Resistance (Ω): 0.05~48
Tolerance (%): ±5, ±10
TCR (ppm/C): 800 max.

Model: DBR
Resistor type: Wire wound
Description: Dynamic braking
Power Rating: 8kW~60kW
Resistance (Ω): 1~150
Tolerance (%): ±5, ±10
TCR (ppm/C): 800 max.

Model: RLB
Resistor type: Wire wound
Description: Load bank
Power Rating: 50kW~3000kW
Resistance (Ω): 0.1~1M
Tolerance (%): ±5, ±10
TCR (ppm/C): 200