Cement Power Resistors, BPR & Non-Inductive Values
Cement power resistors for through-hole loads, current limiting and repair
This collection focuses on ceramic-cased cement resistors, including rectangular wirewound power parts, BPR low-ohm formats, SQP and RX27 listings, and selected products described as non-inductive. Resistance, wattage, body size, lead arrangement and thermal behavior vary by product, so the ceramic case alone does not establish interchangeability.
What is a cement resistor?
A cement resistor is a power resistor enclosed in a heat-resistant ceramic case and filled or bonded with an insulating cement-like material. Many use wirewound construction, while some low-inductance products use a different internal element or winding arrangement. The enclosure helps contain and transfer heat, but it does not make the part cool-running, flameproof, fusible or non-inductive unless those properties are documented.
Products represented
- Rectangular cement resistors: fixed through-hole values in product-specific wattage and tolerance ranges.
- BPR formats: BPR, BPR55 and BPR56 low-ohm products for current limiting or sensing where their exact specifications fit.
- SQP and RX27 listings: ceramic power-resistor families with different dimensions, leads and available values.
- Non-inductive options: selected listings explicitly marked non-inductive; the claim does not cover every product.
- Multi-lead and dual-resistor parts: products with center taps, paired elements or unusual pin arrangements that require circuit-specific matching.
- Temperature-controlled component: one MICRON57 elevator-oriented cement-resistor assembly with a stated thermal function.
How to select
- Choose resistance: distinguish milliohms, ohms and kilohms. For example, 0R22 means 0.22Ω.
- Calculate continuous power: use P = I²R or P = V²/R, then add margin and apply the product's ambient-temperature derating.
- Check pulse energy: continuous wattage does not prove inrush, discharge, braking or repetitive-pulse capacity.
- Verify inductance: use only a product specifically documented as non-inductive where switching speed or frequency response matters.
- Match construction: distinguish ordinary wirewound, BPR low-ohm, cement-film and other stated technologies.
- Check voltage: verify maximum working and overload voltage, particularly for high resistance values.
- Match mechanics: compare body dimensions, lead spacing, lead direction, pin count and PCB clearance.
- Plan cooling: allow airflow and spacing from wiring, plastics and electrolytic capacitors; confirm permissible surface temperature.
BPR versus general cement resistors
BPR parts are commonly offered in low resistance values and may use a different internal geometry from a general rectangular wirewound resistor. A matching resistance and wattage label does not guarantee the same TCR, overload stability, inductance, body size or pinout. For current measurement, verify tolerance, TCR and connection geometry, and use Kelvin routing where required.
Inductive versus non-inductive construction
A conventional wirewound element behaves as both resistance and inductance. That may be acceptable for DC and low-frequency power duties but problematic for fast pulses, snubbers, audio loads or RF work. Only listings explicitly identified and documented as non-inductive should be selected for those requirements; even then, verify residual inductance and frequency behavior.
Power, heat and mounting boundaries
Product titles include multiple power classes, but wattage is valid only under defined thermal conditions. Cement resistors can operate at high surface temperatures. Do not mount them against heat-sensitive materials or assume the PCB alone can tolerate the heat. Check lead temperature, board spacing, ventilation, enclosure temperature and overload conditions.
Load, braking and discharge boundaries
A cement resistor can be used as a load, bleeder, precharge or discharge element only after calculating resistance, continuous power, pulse energy and duty cycle. It is not automatically suitable as a motor-drive braking resistor, amplifier dummy load or mains inrush part. Follow the equipment manufacturer's limits and verify touch-safe and fire-safe installation.
Mixed-product boundaries
Some listings combine ceramic, cement, wirewound, BPR or non-inductive terms. Those terms must be checked at the exact variant level. The MICRON57 product is described for a specific elevator temperature-control application and should not be treated as a universal thermal fuse or ordinary cement resistor. Collection membership does not prove equipment compatibility.
Typical applications
- Power-supply bleeder and discharge paths
- Current limiting and precharge circuits
- Emitter, source and ballast resistance
- Low-frequency dummy loads within thermal limits
- Repair of through-hole power stages using matched dimensions and ratings
- Low-ohm sensing where the exact BPR specification is suitable
Ordering checklist
- Resistance, tolerance and TCR
- Continuous power with derating
- Pulse, surge and overload requirement
- Inductive or documented non-inductive construction
- Working voltage and insulation needs
- Body dimensions, lead spacing and pin arrangement
- Cooling, clearance and surface-temperature plan
- Exact circuit or equipment compatibility
Frequently asked questions
Are all cement resistors wirewound?
No. Many are, but construction varies. Verify the exact product technology.
Does a ceramic case make a resistor flameproof?
No. Flameproof or fusible behavior must be explicitly documented.
Are all products in this collection non-inductive?
No. Only selected listings carry that claim, and their residual inductance still depends on construction.
Can any BPR resistor be used as a current shunt?
No. Check tolerance, TCR, overload stability and connection geometry for the required accuracy.
Can a 10W cement resistor always dissipate 10W?
No. Real capacity depends on ambient temperature, spacing, airflow and the specified derating conditions.
Are equal-value cement resistors direct replacements?
Not necessarily. Match power, pulse behavior, voltage, dimensions, leads, inductance and temperature limits.
Is the MICRON57 part a general replacement?
No. It must match the stated temperature, resistance, current, dimensions and equipment requirements.
