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Dufew Electric Energy Regeneration Unit converts regenerative DC energy from variable frequency drive DC buses into grid-synchronized AC power, allowing recovered energy to be returned to the electrical supply instead of being dissipated through a braking resistor.
In variable frequency drive systems with frequent or sustained regenerative operation, mechanical energy from decelerating motors, high-inertia loads, or descending suspended loads can flow back to the DC bus and cause bus voltage rise. An Energy Regeneration Unit provides an active energy recovery path that converts this DC energy into synchronized AC power and returns it to the grid, reducing heat that would otherwise be generated by resistor-based braking.
The Energy Regeneration Unit operates on the DC side of the VFD and uses an active inverter to transfer regenerative energy back to the AC supply. During regenerative operation, the energy path follows a controlled sequence:
Unlike a conventional braking chopper, the unit does not use a resistor as the main energy-dissipation path. The recovered energy is transferred back to the electrical system, and the unit itself only generates switching and conduction losses associated with the conversion process.
| Comparison | Active Energy Regeneration | Braking Module + Resistor |
|---|---|---|
| Energy handling | Returns regenerated energy to the AC supply | Converts regenerated energy into heat |
| Main application | Frequent or sustained regeneration | Short or intermittent braking |
| Resistor required | Not used as the primary energy path | Required |
| Braking heat | Lower resistor-related heat load | Energy dissipated as heat |
| Energy utilization | Recovered for use by the electrical system | Not recovered |
| Key selection factor | Regenerative power and duty cycle | Braking power and duty cycle |
Neither solution is suitable for every application. For short and infrequent braking events, a resistor-based braking system may be sufficient. Applications with frequent or sustained regeneration require evaluation of the recoverable energy, regenerative power, and operating cycle.
Power conversion stage uses IGBT switching devices and PWM control to convert regenerative DC energy into controlled AC current for grid-side energy recovery.
The inverter regulates feedback current using sinusoidal tracking. Current THD is below 5% under specified operating conditions.
Monitors the VFD DC bus and responds to voltage changes associated with regenerative operation. Threshold depends on system voltage and selected configuration.
Uses the AC supply as reference for voltage, frequency, and phase conditions. Supports automatic phase-sequence identification according to product configuration.
An integrated reactor and filtering components manage inverter switching current and reduce high-frequency interference during energy conversion.
Supported units can operate in parallel with coordinated control. Synchronization response is ≤1 ms for applicable configurations.
Protection functions can include DC-bus overvoltage, AC-side overcurrent, short circuit, overtemperature, grid undervoltage, and phase-related faults. The exact protection set should be confirmed against the selected model's technical documentation.
| Application | Regenerative Condition | Why Energy Recovery Matters |
|---|---|---|
| Elevators | Repeated acceleration, deceleration, and load movement | Frequent regeneration over operating cycles |
| Hoists & Cranes | Lowering suspended loads | Potential energy returned to the DC bus |
| Mine Hoists | Repeated lifting and lowering | Long-duration regenerative operation |
| Centrifuges | High-inertia deceleration | Rotational energy released during braking |
| Test Benches | Repeated motor acceleration and deceleration | Regenerative operation occurs frequently |
| Machine Tools | Rapid spindle deceleration | Short braking cycles generate regeneration |
| Textile Machinery | Repeated speed changes | Regenerative events throughout the cycle |
| Oilfield Equipment | Repetitive mechanical movement | Operating cycles produce recurring regeneration |
Note: Application suitability should be evaluated from actual regenerative power and duty cycle rather than the motor's rated power alone.
The following information represents currently available product data. Final values should be confirmed against the selected model and project specification.
| Parameter | Specification / Selection Basis |
|---|---|
| Conversion Method | IGBT-based PWM active inverter |
| Grid Connection | AC utility supply |
| System Voltage | Available according to selected configuration |
| Energy Conversion | Regenerative DC energy to synchronized AC power |
| Regeneration Efficiency | ≥97% under specified operating conditions |
| Current THD | <5% under specified operating conditions |
| Grid Synchronization | Voltage, frequency, and phase tracking |
| Phase Sequence | Automatic identification according to configuration |
| Filtering | Integrated reactor and noise filtering |
| Cooling | According to selected model |
| Protection | Overvoltage, overcurrent, short circuit, overtemperature, and applicable grid protection |
| Parallel Operation | Available according to system configuration |
| Installation | VFD cabinet or designated electrical enclosure |
| Applicable Standard | GB/T 12668, where applicable |
| Parameter | What to Provide | Why It Matters |
|---|---|---|
| VFD Model | Manufacturer and complete model number | Confirms DC-bus configuration and electrical compatibility |
| System Voltage | 220 V / 380 V / 690 V or applicable | Determines required electrical configuration |
| Motor Power | Rated motor output | Starting reference for system sizing |
| Regenerative Power | Peak and/or continuous regenerative power | Determines required recovery capacity |
| Load Type | Hoisting, high-inertia, overhauling, test bench | Defines the energy-generation pattern |
| Deceleration Time | Required stopping time | Helps determine peak regenerative power |
| Regeneration Frequency | Events per hour, cycle, or shift | Determines operating and thermal requirements |
| Regeneration Duration | Duration of each regenerative event | Important for continuous-duty sizing |
| DC-Bus Voltage | Normal and maximum operating voltage | Confirms compatibility with conversion stage |
| Grid Conditions | Voltage, frequency, and phase configuration | Required for grid-side synchronization |
| Existing Braking System | Braking unit / resistor information | Helps determine integration path |
| Installation Conditions | Cabinet space, cooling, ambient temperature | Determines installation and thermal requirements |
Dufew Electric manufactures power electronics components for industrial drive and power-control applications, with production and inspection procedures covering key electrical, functional, and safety-related requirements.
For an energy regeneration unit, applicable procedures may include IGBT and power-component inspection, PCB assembly inspection, electrical connection inspection, insulation testing, functional testing, protection-function verification, temperature-control verification, grid-side operation testing, and final product inspection. Model-specific test records and technical documents can be provided according to project requirements.
Certification: The supplied product information indicates compliance with GB/T 12668 where applicable. Dufew Electric also maintains ISO and CE-related quality and product compliance documentation. Applicable certificates should be confirmed according to the specific model, configuration, and destination market.
It converts regenerative energy from a VFD DC bus into AC power that can be returned to the utility grid. It is mainly considered for applications with frequent, high-power, or sustained regenerative operation.
Dynamic braking sends regenerative energy to a resistor, where it is converted into heat. Energy regeneration converts the DC energy into synchronized AC power and returns it to the electrical system.
In a properly designed regeneration system, the unit can replace the resistor-based energy dissipation path. However, the existing VFD, DC-bus configuration, protection system, and application duty must be checked before making the change.
Not automatically. Compatibility depends on the VFD's DC-bus voltage, power configuration, electrical interface, load characteristics, and the unit's grid-side requirements. The specific VFD model should be provided for selection.
Parallel operation can be used when additional regeneration capacity is required, provided that selected models support parallel operation and the DC-bus, AC-side connection, synchronization, and thermal conditions are correctly designed.
It can reduce heat from regenerative braking because recovered energy is transferred back to the electrical system rather than being dissipated entirely through a resistor. The unit itself still produces electrical and switching losses and requires appropriate cooling.
Key information includes system voltage, VFD model, motor power, load type, regenerative power, deceleration time, regeneration frequency, regeneration duration, DC-bus voltage, and installation conditions.
Send us your VFD model, system voltage, motor power, load type, regenerative power, and installation conditions. Dufew Electric will evaluate the application and provide a technical recommendation.
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