CRA Series Ceramic Resistor Assemblies
Pre-assembled stacked bulk ceramic washer resistor unit — six ceramic washer elements per assembly
Continuous power rating 50W per element — 300W total per assembly
Peak energy rating 130,000 joules per element — 780,000 joules total per assembly
Tolerance options ±5%, ±10%, and ±20%
Negative TCR −500 to −1500 ppm/°C — resistance decreases as temperature rises
Inherently non-inductive construction — energy dissipated uniformly through the entire ceramic mass of all six elements
Ready-to-install format — eliminates on-site stacking, alignment, and terminal assembly of individual washer components
Contact surfaces metallised in aluminium or brass; anti-track coating available between contact areas
What are the CRA Series Ceramic Resistor Assemblies?
The CRA is a factory-assembled ceramic resistor unit built from a coaxial stack of six bulk ceramic washer elements (83-W series) mounted on a common threaded stud with inter-element contact metallisation, end terminals, and mechanical clamping hardware pre-installed. Where the 83-W is supplied as an individual washer for the designer to configure into a stack in the field, the CRA delivers that stack as a single finished assembly ready for direct installation onto a bus bar, terminal post, or panel fixture. Each of the six washer elements contributes 50W of continuous power dissipation and 130,000 joules of peak energy absorption capacity, giving the CRA assembly a total continuous rating of 300W and a total peak energy capacity of 780,000 joules in a single mountable unit.
Each ceramic washer within the CRA assembly is manufactured by sintering resistive particles in a binding medium, producing a dense homogeneous annular body whose resistive material is distributed uniformly throughout the full thickness of the ceramic wall rather than being confined to a surface film or wound wire. This bulk construction means that surge and pulse energy is spread across the entire ceramic volume of all six elements simultaneously, and there is no surface layer to delaminate and no helical conductor to rupture under fault-level transients. The construction is inherently non-inductive, so the CRA presents a purely resistive impedance at switching frequencies and during fast transient events where wirewound assemblies of equivalent energy rating would introduce significant inductive reactance and overshoot. The negative temperature coefficient of resistance (TCR) of −500 to −1500 ppm/°C, shared with all 83-series ceramic components, means the assembly’s resistance falls as it absorbs energy and heats up, allowing circuits to transition naturally from a high-impedance inrush-limiting state to a lower-impedance operating condition without active switching.
The factory-assembled format of the CRA addresses a practical challenge inherent in high-energy washer stacks: ensuring consistent contact pressure, correct element alignment, and reliable inter-element electrical continuity across six ceramic bodies in a heavy industrial environment where vibration, thermal cycling, and mechanical shock are routine. By supplying the stack as a pre-assembled, pre-tested unit with all hardware torqued and verified, the CRA eliminates the risk of improper field assembly and reduces installation time to a single mounting operation. Tolerance options of ±5%, ±10%, and ±20% are available across the assembly, and contact surfaces within the stack use either aluminium or brass metallisation. An anti-track coating is available on the outer and inner diameter surfaces of the washer elements between the contact bands, extending the operating voltage headroom in high-voltage, humid, or contaminated service environments.
CRA Series Ceramic Resistor Assemblies Specifications
A practical overview for engineers and procurement teams evaluating resistive solutions.
Model: CRA
Resistor type: Bulk Ceramic
Description: Ceramic Resistor Assembly
Power Rating: 50W x 6, 130,000joules x 6
Tolerance (%): ±5, ±10, ±20
TCR (ppm/C): -500~-1500
Applications of the CRA Series Ceramic Resistor Assemblies
Where RARA ceramic resistors are deployed in the field.
Dynamic braking and chopper resistors for large AC and DC motor drives — the assembly absorbs regenerated kinetic energy returned from the motor during deceleration, preventing DC bus overvoltage shutdown, in a single bolt-on unit rated to 300W continuous and 780,000 joules peak
Crowbar resistor assemblies for emergency energy dumping — the 780,000-joule peak energy capacity across six elements allows the CRA to absorb the full stored energy of large capacitor banks or rotating machinery in a single fault event, as required for wind turbine and transport power emergency shutdown systems
Capacitor bank charge and discharge circuits — factory-assembled stacked format ensures consistent contact integrity under repetitive high-energy charge-discharge cycles that would risk individual washer displacement or contact degradation in a field-assembled stack
Impulse voltage generators and high-voltage pulse circuits — non-inductive assembly handles high-energy single-shot and repetitive pulse duties without inductive overshoot; pre-tested assembly ensures reliable performance under repeated impulse stress
High-power soft-start and inrush current limiting — negative TCR of all six washer elements acts in concert to limit peak inrush at startup and reduce resistance naturally as the assembly warms to steady-state operating temperature, without active control
Electrical transmission and distribution protection — compact stacked assembly integrates into switchgear and bus bar installations for fault current limiting and surge absorption at power distribution voltage levels
Industrial motor starting and soft-start panels — the pre-assembled format simplifies panel wiring and reduces installation time compared to individually mounted washer resistors, with a single terminal connection at each end of the assembly
Wind turbine and transport traction power protection — the combination of extreme peak energy capacity, robust ceramic construction, and factory-verified mechanical integrity makes the CRA suited to the emergency protection duties required in wind energy converters and rail traction drives
High-energy load testing and acceptance test systems — stable, non-inductive assembly provides a reliable high-power reference load for acceptance testing and power quality measurement of large drives, generators, and power conditioning equipment
Replacement and retrofit of field-assembled washer stacks — the CRA provides a drop-in factory-built alternative wherever individually stacked 83-W washers are currently in service but where improved assembly reliability, reduced maintenance, or simplified spare-parts management is required
Related Products of the CRA Series Ceramic Resistor Assemblies
Model: 83-A
Resistor type: Bulk Ceramic
Description: Axial lead rods
Power Rating: 2.2W~7W
Resistance (Ω): 6~977k
Tolerance (%): ±5, ±10, ±20
TCR (ppm/C): -500~-1500
Model: 83-T
Resistor type: Bulk Ceramic
Description: Tubes
Power Rating: 12W~352W
Resistance (Ω): 1~295k
Tolerance (%): ±5, ±10, ±20
TCR (ppm/C): -500~-1500
Model: 83-R
Resistor type: Bulk Ceramic
Description: Rods
Power Rating: 4.7W~445W
Resistance (Ω): 0.9~244k
Tolerance (%): ±5, ±10, ±20
TCR (ppm/C): -500~-1500
Model: 83-W
Resistor type: Bulk Ceramic
Description: Organic, washers
Power Rating: 3.8W~327W
Resistance (Ω): 20m~6.8k
Tolerance (%): ±5, ±10, ±20
TCR (ppm/C): -500~-1500
Why Choose RARA Ceramic Resistors
What sets RARA apart for engineers and procurement managers in industrial and automotive markets.
01
Unique Negative TCR
The -500 to -1500 ppm/°C negative TCR is a fundamental property of sintered bulk ceramic — exploited in inrush limiting, soft-start, and temperature compensation circuits where resistance must decrease with temperature rise.
02
Surge Tolerant by Design
The bulk distributed construction absorbs pulse and surge energy throughout the entire volume of the component — giving ceramic resistors exceptional pulse handling capability compared to surface-film types of equivalent power rating.
03
Five Form Factors
Axial rods, bare tubes, bare rods, washers, and disks — five geometries covering through-hole PCB, chassis, in-line bus bar, and panel mounting requirements in a single product family.
04
Global Track Record
Trusted by Siemens, Rockwell, Schneider Electric, and Hanwha — deployed in industrial power electronics, inrush protection, and surge limiting applications across six continents.
