A braking resistor is required when the Hope65 VFD must stop a high-inertia or regenerative load quickly. During deceleration, the motor can act like a generator and feed energy back into the VFD DC bus. If this energy is not discharged, the DC bus voltage rises and the VFD may trip with overvoltage faults such as E06 deceleration overvoltage or E07 constant-speed overvoltage.
Connect the external braking resistor only to the designated PB and (+) braking terminals. Do not connect the braking resistor to U/V/W, R/S/T, L1/L2, PE, relay, or control terminals.
Select the resistor by matching the exact Hope65 model, braking torque requirement, duty cycle, resistance value, power rating, and minimum allowed resistance. Never use a resistor below the specified minimum resistance for the VFD model.
Only trained and qualified electrical personnel should select, wire, install, test, or replace a VFD braking resistor.
Before touching VFD terminals, braking resistor terminals, or panel wiring, switch off all input power, wait at least 10 minutes, and confirm that the DC bus voltage has discharged to a safe level.
Braking resistors become very hot during operation. Install them away from plastic, paper, cable bundles, oil, dust accumulation, or flammable material.
This article explains how to decide whether a braking resistor is required for the Hope65 Series Smart AC Drive / VFD, how to select the correct resistor, how to wire it to PB and (+), how to mount it safely, and how to troubleshoot braking-related overvoltage or resistor faults.
Use this guide when the VFD trips during stopping, the machine requires rapid deceleration, the load has high inertia, the fan continues spinning, the conveyor pulls the motor during stopping, or the system reports voltage-related faults such as E06, E07, E08, or braking resistor-related errors.
01 Identify LoadCheck if the machine has high inertia, fast stop demand, gravity load, windmilling fan, or regenerative running. | 02 Select ResistorUse the correct resistance and wattage for the exact Hope65 model and braking duty cycle. | 03 Wire SafelyConnect only to PB and (+), use suitable cable, mount in a cooled flame-retardant location, then test at low speed. |
| Product Series | Slanvert Hope65 Series Smart AC Drive / VFD |
| Power Range | 0.75 kW to 22 kW Hope65 models covered by this article |
| Terminal Scope | PB and (+) external braking resistor terminals |
| Typical Applications | Fans, blowers, conveyors, mixers, centrifuges, windmilling loads, fast-stop machines, high-inertia equipment, and controlled deceleration systems |
| User Level | Qualified electrical technician, panel builder, machine integrator, automation engineer, or maintenance engineer |
When a VFD accelerates a motor, electrical energy flows from the supply through the drive to the motor. During normal deceleration, the VFD reduces output frequency and the motor slows down. However, if the motor is connected to a high-inertia or externally driven load, the load may continue rotating and force the motor to generate energy.
This generated energy flows back into the VFD DC bus. If the DC bus voltage rises above the permitted level, the VFD protects itself by tripping with an overvoltage fault. A braking resistor provides a controlled path to discharge this excess energy as heat.
01 Load Inertia
| → | 02 Motor Generates
| → | 03 Braking Resistor
|
| Main rule: If the VFD trips during deceleration and the issue improves when deceleration time is increased, the original stop time may be too aggressive for the load. A braking resistor may be required if fast stop is still needed. | ||||
| Condition | Why It Needs Braking | Typical Symptom Without Resistor |
|---|---|---|
| Short deceleration time | The VFD must absorb energy quickly during stopping. | E06 deceleration overvoltage. |
| Large fan or blower | The impeller stores high rotating energy and may windmill. | Overvoltage during stop or restart. |
| Conveyor with heavy load | Moving material can pull the motor during deceleration. | Overvoltage or uncontrolled coast after stop command. |
| Mixer, drum, centrifuge, roller | Rotating mass continues moving after frequency is reduced. | Trip during deceleration or inability to meet stop time. |
| Frequent start/stop cycle | Repeated braking creates repeated heat load in the resistor. | E08 buffer resistor overload or overheating resistor. |
| Hoist or vertical load | Gravity can drive the motor and regenerate energy. | Overvoltage, unsafe motion, or brake timing issue. Requires specialist design. |
A braking resistor is not automatically required for every VFD installation. Many pumps, fans, and light-duty machines can stop safely by increasing the deceleration time.
| Condition | Recommended First Step | Why |
|---|---|---|
| Light load | Increase deceleration time and retest. | The load may not generate enough energy to need resistor braking. |
| Long stopping time acceptable | Use longer F0-14 deceleration time. | Longer deceleration reduces regenerative energy rate. |
| Pump with normal coast-down | Check process valve and water hammer before adding resistor. | Process control may be more important than braking torque. |
| No E06/E07 fault during stop | Do not add resistor unless process requires faster stopping. | Unnecessary resistor adds heat, wiring, panel space, and maintenance risk. |
Step 1 Confirm VFD ModelUse the exact Hope65 model number from the nameplate. | Step 2 Check Load TypeIdentify inertia, stop time, cycle frequency, and regenerative behavior. | Step 3 Choose ResistanceUse recommended braking resistor value and never go below minimum resistance. |
Step 4 Choose PowerUse duty cycle: 10%, 50%, 80%, or application-specific higher power rating. | Step 5 Mount SafelyInstall in a well-cooled flame-retardant area away from cables and material. | Step 6 Test GraduallyStart at low speed and verify E06/E07 no longer occurs. |
Use the table below as a selection reference. Always verify the exact model number from the VFD nameplate before ordering or installing a resistor.
| Hope65 Model | Braking Unit | Resistor at 100% Braking Torque | Power at 10% Duty | Power at 50% Duty | Power at 80% Duty | Minimum Resistance |
|---|---|---|---|---|---|---|
| Hope65G0.75S2B | Built-in | 192 Ω | 0.11 kW | 0.56 kW | 0.90 kW | 42 Ω |
| Hope65G1.5S2B | Built-in | 96 Ω | 0.23 kW | 1.10 kW | 1.80 kW | 30 Ω |
| Hope65G2.2S2B | Built-in | 65 Ω | 0.33 kW | 1.70 kW | 2.64 kW | 21 Ω |
| Hope65G4S2B | Built-in | 43 Ω | 0.33 kW | 1.68 kW | 2.70 kW | 12 Ω |
| Hope65G5.5S2B | Built-in | 31 Ω | 0.46 kW | 2.30 kW | 3.70 kW | 8 Ω |
| Hope65G0.75/P1.5T4B | Built-in | 635 Ω | 0.10 kW | 0.60 kW | 0.90 kW | 240 Ω |
| Hope65G1.5/P2.2T4B | Built-in | 326 Ω | 0.23 kW | 1.10 kW | 1.80 kW | 170 Ω |
| Hope65G2.2/P4T4B | Built-in | 222 Ω | 0.33 kW | 1.70 kW | 2.60 kW | 130 Ω |
| Hope65G4/P5.5T4B | Built-in | 122 Ω | 0.60 kW | 3.00 kW | 4.80 kW | 80 Ω |
| Hope65G5.5/P7.5T4B | Built-in | 89 Ω | 0.75 kW | 4.10 kW | 6.60 kW | 60 Ω |
| Hope65G7.5/P11T4B | Built-in | 65 Ω | 1.10 kW | 5.60 kW | 9.00 kW | 47 Ω |
| Hope65G11/P15T4B | Built-in | 44 Ω | 1.70 kW | 8.30 kW | 13.20 kW | 31 Ω |
| Hope65G15/P18.5T4B | Built-in | 32 Ω | 2.00 kW | 11.00 kW | 18.00 kW | 23 Ω |
| Hope65G18.5/P22T4B | Built-in | 27 Ω | 3.00 kW | 14.00 kW | 22.00 kW | 19 Ω |
| Hope65G22/P30T4B | Built-in | 22 Ω | 3.00 kW | 17.00 kW | 26.00 kW | 17 Ω |
The resistor power rating depends on how often and how long braking occurs. A resistor that works for occasional stopping may overheat if the machine stops frequently.
| Duty Level | Meaning | Typical Application | Selection Rule |
|---|---|---|---|
| 10% braking duty | Occasional braking with cooling time between stops. | Simple fan or conveyor stopping occasionally. | Use only when braking is infrequent. |
| 50% braking duty | Frequent or medium-duty braking. | Conveyors, indexing machines, frequent speed changes. | Use higher power resistor and verify thermal mounting. |
| 80% braking duty | Heavy-duty braking with high heat load. | Centrifuge, high-inertia drum, rapid cyclic stopping. | Use carefully selected high-power resistor and thermal protection. |
| Above 10% frequent braking | Braking is more frequent than light-duty selection. | High-cycle machine, frequent start/stop production line. | Select more power than the light-duty table value according to actual working condition. |
The braking resistor wiring is simple but high-risk if done incorrectly. The resistor must be connected only to the Hope65 braking resistor terminals.
Hope65 VFD PB and (+)
| → | External Resistor BR
| → | Energy Dissipation Heat
|
| Do not connect the braking resistor to any terminal except PB and (+). Wrong wiring can damage the braking circuit, damage the VFD, and create fire risk. | ||||
Braking resistors convert electrical energy into heat. The resistor can become extremely hot during braking. Mechanical installation must be planned as carefully as electrical wiring.
| Installation Item | Correct Practice | Risk If Wrong |
|---|---|---|
| Mounting location | Install in a well-cooled location with free air movement. | Resistor overheating, E08 fault, fire risk, cabinet overheating. |
| Nearby material | Keep flame-retardant material around the resistor. | Plastic, cable insulation, dust, or oil can overheat or ignite. |
| Cable routing | Use suitable shielded/high-temperature cable and secure it mechanically. | Loose wiring, electrical noise, insulation damage, or terminal overheating. |
| Panel ventilation | Ensure heat from resistor does not raise VFD cabinet temperature above safe level. | VFD overheat, shortened component life, repeated trips. |
| Human access | Guard or label the resistor area to prevent accidental touch. | Burn injury due to high resistor temperature. |
Braking resistor installation is mainly a hardware task, but stop behavior and overvoltage behavior also depend on drive parameters. Change parameters only after confirming machine safety.
| Parameter / Group | Purpose | Braking Relevance |
|---|---|---|
| F0-14 | Deceleration time 1 | Short deceleration time increases regenerative energy rate and can trigger E06. |
| F1-06 | Stop method | Deceleration stop uses ramp control. Free stop lets motor coast and does not control deceleration time. |
| F1 acceleration/deceleration method | Linear or S-curve ramp | S-curve can reduce mechanical shock during speed change but does not replace correct resistor sizing. |
| F8-03 | Overvoltage stall gain | Affects overvoltage stall response. Adjust only with technical understanding. |
| F8-04 | Overvoltage stall protection voltage | Defines overvoltage stall protection threshold behavior. |
| F8-13 to F8-15 | Fault history | Confirms whether the issue is E06 deceleration overvoltage, E07 constant-speed overvoltage, E08 buffer resistor overload, or braking resistor short circuit. |
| Fault | Meaning | Likely Braking-Related Cause | First Action |
|---|---|---|---|
| E05 | Acceleration overvoltage | Motor/load may already be rotating or externally driven during start. | Check load rotation, input voltage, speed tracking need, and braking design. |
| E06 | Deceleration overvoltage | Deceleration time too short, high inertia, no braking resistor, or resistor under-sized. | Increase F0-14 deceleration time. If fast stop is required, install/select correct resistor. |
| E07 | Constant-speed overvoltage | Load drives motor during operation, windmilling fan, gravity or process back-drive. | Check regenerative load behavior and braking resistor requirement. |
| E08 | Buffer / snubber resistor overload | Abnormal voltage condition, repeated stress, or power/braking issue. | Check input voltage, braking duty, and resistor installation condition. |
| Fault history value 38 | Braking resistor short circuit | Wrong resistor, damaged resistor, shorted wiring, or incorrect terminals. | Power OFF, discharge, inspect resistor and PB/(+) wiring before reset. |
| Application | Braking Risk | Recommended Approach |
|---|---|---|
| Fan / blower | High inertia and windmilling can regenerate energy. | Use longer deceleration first. Add resistor if fast stop or frequent stop is required. |
| Conveyor | Heavy material can pull motor during stop. | Check load direction, brake timing, and stop time. Use resistor for rapid stop. |
| Mixer / drum / centrifuge | Large rotating inertia stores high energy. | Select higher duty resistor and allow cooling time between stops. |
| Pump | Usually less braking demand, but reverse flow or pressure can back-drive. | Check process valve, water hammer, and stop ramp before adding resistor. |
| Hoist / vertical load | Gravity regeneration and safety risk. | Do not trial randomly. Use specialist design with mechanical brake, braking resistor, and safety review. |
| Problem | Likely Cause | Corrective Action |
|---|---|---|
| E06 during deceleration | Deceleration too short, resistor not installed, wrong resistor value, or resistor disconnected. | Increase deceleration time, check PB/(+) wiring, and verify resistor selection. |
| Resistor becomes extremely hot quickly | Duty cycle too high, resistor power rating too low, repeated braking, poor ventilation. | Use higher power resistor, improve cooling, increase stop time, or reduce braking frequency. |
| Braking resistor short circuit fault | Shorted resistor cable, damaged resistor, incorrect resistance, or wrong terminal wiring. | Power OFF, discharge, inspect resistor and wiring before reset. |
| No improvement after resistor installation | Wrong terminals, open resistor circuit, incorrect resistor value, or issue is input overvoltage rather than regeneration. | Check PB/(+) wiring, measure resistor continuity, and check input voltage. |
| E08 buffer resistor overload | Abnormal voltage range, heavy repeated braking, or power/braking circuit stress. | Check input voltage, resistor duty, cooling, and braking cycle. |
| Cable insulation damage near resistor | Cable routed too close to hot resistor body. | Re-route cable, use heat-resistant cable where needed, and add mechanical protection. |
To reduce troubleshooting time, share the following information:
Smidnya technical support can help review your Hope65 model, motor rating, load inertia, stop time, braking duty cycle, resistor resistance, resistor wattage, PB/(+) wiring, and overvoltage fault history before commissioning.