Braking Resistors for VFDs / AC Drives
When a VFD-driven motor decelerates a high-inertia load (centrifuge, conveyor, fan), the motor acts as a generator and regenerates energy onto the DC bus. Without somewhere to dump it, bus voltage rises and trips the drive's over-voltage fault. A braking resistor sized for the duty cycle absorbs this energy as heat. Typical industrial drives chop the bus through an IGBT brake module at 10–30% duty; resistor sizing must satisfy both peak power (during deceleration) and continuous average power (across the cycle). Hongyi supplies aluminum-housed and corrugated braking resistors from 100 W to 50 kW per unit, IEC 60322 compliant, with built-in thermostats (NC/NO contact, 120°C trip) for fail-safe drive shutdown. We also supply IP54/IP65 cabinet-mount versions for ABB, Siemens, Schneider, Yaskawa, Danfoss, Delta and Inovance drives.
Key Requirements
- Peak power = ½ × J × (ω₁² − ω₂²) / t_dec — must match the drive's brake-IGBT current rating
- Continuous power = peak × duty cycle (typical 5–25% for industrial cycles)
- Resistance value matched to drive's brake chopper trip voltage (380 V → 47–80 Ω; 690 V → 8–14 Ω)
- Thermostat or PT100 sensor for over-temp shutdown (typical 120°C NC contact)
- IP20 for cabinet mount, IP54/IP65 for outdoor or wash-down environments
- IEC 60322 compliance for short-time overload (5× rated for 5 s minimum)
How to Select
- Get J (load inertia, kg·m²), ω₁ (start), ω₂ (end speed) and t_dec from the mechanical designer
- Cross-check resistance against drive manufacturer's recommended min/max (in the drive manual)
- Add 1.5× safety margin on continuous power for ambient ≥ 40°C or altitude > 1000 m
- Choose corrugated/edge-wound for >10 kW where surface area drives natural cooling
- For frequent-stop applications (>10 brakes/min) consider forced-air or water-cooled cabinet
- Wire to drive's external thermal trip input — never rely on resistor temperature alone
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What braking resistor do I need for a 22 kW ABB ACS580 drive?
Why does my brake resistor get red-hot even though my drive's manual says it's correctly sized?
Can I parallel two smaller braking resistors instead of buying one large unit?
Do braking resistors need a separate IGBT brake chopper, or do drives have it built in?
Sample Request
Standard samples are provided free of charge in reasonable quantities (shipped within 2–3 business days). Custom samples are delivered within 2–4 weeks. Please use the form on the right to tell us:
- Company and contact details
- Target part number or key specs (power / resistance / package)
- Application scenario and estimated annual volume
- Shipping address and expected delivery date