Discharge Resistor: Resistance Range 10kΩ to 10MΩ

Q: What happens if a discharge resistor fails?

Failure can leave capacitors charged at dangerous voltages, creating shock hazards, potential arc flashes during maintenance, and possible capacitor dielectric breakdown from sustained overvoltage.

Component Specifications

Definition

A discharge resistor is a critical safety component in capacitor bank arrays, designed to provide a controlled path for discharging stored electrical energy after system de-energization. It prevents dangerous residual voltage that could cause electric shock, equipment damage, or fire hazards. These resistors are typically connected in parallel with capacitor banks and feature specific power ratings, resistance values, and thermal characteristics to handle discharge currents without overheating or degradation.

Working Principle

The discharge resistor operates on Ohm's Law (V=IR), providing a controlled resistance path for capacitor discharge. When the capacitor bank is disconnected from the power source, the resistor creates a circuit that allows stored energy to dissipate as heat through the resistor material. The discharge time constant (τ = R×C) determines how quickly the voltage decays to safe levels, with proper sizing ensuring discharge within required safety timeframes (typically to less than 50V within specified minutes).

Materials

High-temperature ceramic or metal alloy resistive elements (nichrome, kanthal, or ceramic composites), alumina or steatite ceramic substrates, high-temperature silicone or epoxy encapsulation, nickel-plated copper or stainless steel terminals, ceramic or mica insulation layers.

Technical Parameters

Parameter	Typical range	Notes & selection driver
Power Rating	5W to 500W
Discharge Time	≤ 5 minutes to 50V
Voltage Rating	1kV to 15kV
Resistance Range	10kΩ to 10MΩ
Dielectric Strength	2× rated voltage + 1000V
Insulation Resistance	≥ 1000 MΩ
Operating Temperature	-40°C to +200°C
Temperature Coefficient	±100 to ±500 ppm/°C

Ranges are indicative industry figures for RFQ preparation, not a supplier commitment. Confirm every value and standard with the legal manufacturer before ordering.

Standards

IEC 60243, IEC 60076, UL 94, DIN EN 60115

Parent Products

This component is used in the following industrial products

Capacitor Bank Array

A modular assembly of multiple capacitor banks designed for industrial power factor correction applications.

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Engineering Analysis

Risks & Mitigation

Electric shock from residual voltage
Thermal runaway from insufficient power rating
Insulation breakdown from moisture ingress
Mechanical failure from vibration stress
Corrosion of terminals in harsh environments

FMEA Triads

Trigger: Overheating due to excessive discharge current
Failure: Resistance value drift or open circuit
Mitigation: Implement thermal protection, use resistors with adequate power derating, and ensure proper ventilation

Trigger: Moisture absorption in encapsulation
Failure: Reduced insulation resistance leading to leakage current
Mitigation: Use moisture-resistant materials, conformal coating, and sealed enclosures

Trigger: Mechanical stress from vibration
Failure: Cracked resistive element or broken connections
Mitigation: Secure mounting with vibration dampeners and use flexible lead connections

Industrial Ecosystem

Compatible With

Typical Suppliers & Equivalents

Compliance & Inspection

Tolerance

Resistance tolerance typically ±5% to ±10%, power rating derated by 50% at maximum operating temperature

Test Method

High-pot testing at 2× rated voltage + 1000V for 60 seconds, resistance measurement at 25°C ±5°C, thermal cycling from -40°C to +125°C for 100 cycles, humidity testing at 85% RH and 85°C for 1000 hours

Procurement Evaluation Criteria

A practical evidence checklist for RFQ preparation and supplier evaluation.

Technical documentation

Request current drawings, revision history, and a signed specification sheet.

Manufacturing capability

Verify equipment lists, process limits, capacity, and representative production evidence.

Inspection readiness

Confirm test methods, calibrated equipment, sampling plans, and traceable reports.

Supplier transparency

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Manufacturers of Discharge Resistor

Manufacturer profiles associated with Discharge Resistor.

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Frequently Asked Questions

Why are discharge resistors necessary in capacitor banks?

Discharge resistors are essential for safety, preventing hazardous voltage buildup that could cause electric shock, equipment damage, or fire when capacitors retain charge after system shutdown.

How do you calculate discharge resistor values?

Resistance is calculated using R = t / (5×C), where t is desired discharge time (seconds) and C is capacitance (farads), ensuring voltage drops to safe levels (typically <50V) within required timeframes.

What happens if a discharge resistor fails?