Four-quadrant
operation
Motoring and regenerative operation in both directions, engineered around the application’s load cycle.
Project referencesMetals & steelIndonesia
INDONESIA · STEEL INDUSTRY
Four-Quadrant Regenerative AC Drive Solution for an Indonesian Steel Mill
DC-to-AC Drive Modernization · Multi-Motor Roller Conveyors · Low-Harmonic Regenerative Technology
INOMAX supplied an engineered ACS880 regenerative drive system for the steel plant’s AC motor application, combining multi-motor control, AFE-based cabinet engineering and competitive project pricing.
298AC motors
4,370 kWConnected motor nameplate power
305Roller sets in the final schedule
2Main drive groups
01 / PROJECT OVERVIEW
Project Overview
DC-to-AC drive modernization with four-quadrant regenerative technology for an Indonesian steel plant.
The customer previously used a legacy DC motor and drive arrangement. Its modernization project moved to an AC motor drive solution, with machinery and motors sourced from an Italian supplier and the drive system supplied by INOMAX. This case focuses on the multi-motor roller conveyor drive package.
INOMAX configured a four-quadrant, low-harmonic regenerative AC drive solution around the approved motor groups and electrical design. The package combines Active Front End (AFE) supply, a common DC bus, motor-side inverter modules and engineered drive cabinets.
The project partner, a system integrator supplying ABB and Siemens solutions, evaluated both ABB and INOMAX proposals. Lower project pricing and a shorter lead time supported the INOMAX offer; factory and steel-plant reference visits gave the customer confidence to proceed.
02 / PROJECT REQUIREMENTS
Modernizing DC Drives
for a Multi-Motor AC System
The modernization combined the transition to AC motors with motor-group selection, regenerative power-flow requirements and practical cabinet engineering.
- DC-to-AC drive modernizationDevelop the AC drive configuration around the replacement motor specifications, mechanical requirements, speed and torque needs, and control interfaces.
- Multi-motor roller conveyor controlAssign motors to suitable conveyor groups and select each inverter for the group’s connected load and operating conditions.
- Regenerative and low-harmonic designCoordinate AFE supply, filtering, common DC distribution and motor-side modules to support the required power flow and electrical network conditions.
- Engineered cabinets and deliveryTranslate the approved motor schedule and electrical design into cabinet layouts, manufacturing, inspection, packing and shipment.
Project constraints
The end customer needed equipment urgently and was sensitive to price. Technical suitability, delivery lead time and purchase cost all influenced the final supplier decision.
03 / INOMAX SOLUTION
An engineered regenerative AC drive system
The project package combined four-quadrant regenerative capability with a multi-cabinet arrangement tailored to the roller conveyor system.
Four-quadrant
Low-harmonic AFE
Active Front End architecture integrated with the project’s filter and electrical design.
Multi-motor groups
Drive ratings and motor grouping based on the approved motor schedule.
Cabinet engineering
TR5 and TR6 cabinet layouts for an integrated industrial drive lineup.
Explore the drive technology and motor groupingRegenerative energy flow, selected motor groups and engineering scope
Regenerative Energy Recovery
During suitable deceleration, braking or other generating conditions, a regenerative drive system can return eligible motor braking energy to the electrical supply. This provides an alternative to dissipating that energy as heat in braking resistors.
Where steel rolling or roller conveyor duties involve braking and reversing, energy recovery can reduce net energy drawn from the grid. The result depends on the load profile, braking frequency, operating cycle and system configuration.
Low-Harmonic AFE and Motor-Group Control
The low-harmonic drive architecture combines active power conversion with the project’s filter and electrical design. Harmonic performance and regenerative operation must be evaluated for the actual network and operating conditions.
A common DC bus serves multiple SMM inverter modules. Each module is selected for its assigned roller motor group or individual auxiliary duty, keeping the configuration tied to the approved motor schedule.
ILLUSTRATIVE POWER FLOW
Motoring and regenerative operation
AC NETWORKAC supplyProject AC input
SUPPLY UNITSAFE supply unitsRegenerative power conversion
COMMON DC BUS
INVERTER MODULESMM group A
↓Output reactor↓
Roller motor group
INVERTER MODULESMM group B
↓Output reactor↓
Roller motor group
INVERTER MODULESMM group C
↓Output reactor↓
Roller motor group
Public-facing architecture illustration, not an installation or wiring drawing. Individual motor protection is a separate part of the project integration scope.
Motoring: power flows from the electrical supply through the AFE and common DC bus to the inverter modules and motor groups.
ONE MODULE, MULTIPLE MOTORS
See the motor grouping.
Three examples from the final selection schedule. Select a group to see its motor load and INOMAX module.
Exit Furnace Rollers · Section 1
6×18.5 kW=111 kW
Motor nameplate current total228 A
Selected INOMAX inverter moduleACS880-R72-293A-3+SMM
Output reactor in the scheduleOCL-2.2V/330A
6 × 38 A motor nameplate current. Selection is specific to this project’s load and operating requirements.
PROJECT-SPECIFIC ENGINEERING
From the motor list
to the connection interfaces.
Engineering package
- Motor and roller conveyor schedules
- Motor-group drive and reactor selections
- Electrical single-line design
- Cabinet layouts and motor output connections
Control interfaces
- Start/stop and forward/reverse commands
- Emergency-stop interface
- Running and fault status
- Analog frequency and current signals
04 / PROJECT DATA
Project Scale
and Technical Data
The final INOMAX motor and drive schedule defines the roller conveyor scope below. These figures describe this drive package, rather than the steel mill’s entire electrical installation.
Application and supply scope
| Industry | Steel manufacturing |
|---|---|
| Application | Roller conveyor drive system |
| End-user location | Indonesia |
| Project integrator | System integrator supplying ABB and Siemens solutions |
| Drive architecture | Four-quadrant regenerative, low-harmonic AFE system with a common DC bus and modular motor-drive sections |
| Equipment and motors | Sourced from an Italian supplier |
| Drive system supplier | INOMAX |
FINAL MOTOR SCHEDULE
298 motors · 305 roller sets
| Drive group | Motors | Motor rated power |
|---|---|---|
| TR5 | 131 | 2,533 kW |
| TR6 | 167 | 1,837 kW |
| Total | 298 | 4,370 kW |
- TR5 application scope
- Furnace exit, descaling, entry zone, blooming and slab discharge
- TR6 application scope
- Exit zones, leveling, cooling-bed and shear roller sections
4,370 kW is the sum of connected motor nameplate ratings. It is not the AFE rating or measured simultaneous demand.
Source: final INOMAX roller conveyor motor and drive list, 9 July 2024. Final scope is kept separate from the earlier ABB–INOMAX comparison-stage schedule.
05 / DRIVE SELECTION & CUSTOMER DECISION
Drive Selection:
INOMAX and ABB Proposals
The customer compared motor-group configurations, AFE supply, inverter selections and output reactors against the project requirements. The tables below summarize the original proposal-stage selections.
01 / SUPPLY SIDE
AFE arrangement: five parallel units versus four.
The comparison-stage schedule lists the following arrangement for each of its two supply groups.
Swipe the table to compare both proposals →
| Supply arrangement | ABB proposal | INOMAX proposal |
|---|---|---|
| For each of the two supply groups |
5 units in parallelACS880-907-0900A-3 | 4 units in parallelACS880-2R86-1480A-3 |
AFE comparison from the proposal-stage schedule dated 25 May 2024, repeated for both supply groups. These configurations are shown as proposed; final equipment sizing followed the subsequent project engineering and motor schedule.
02 / MOTOR SIDE
Inverter selections for the same motor-group loads.
Each comparison below pairs the ABB and INOMAX module specified for the listed load, together with the output reactor in the schedule.
Swipe the table to compare both proposals →
| Motor group / connected load | ABB proposal | INOMAX proposal | Listed output reactor |
|---|---|---|---|
| 6 × 18.5 kW111 kW · 228 A | ACS880-107-300A-3 | ACS880-R72-293A-3+SMM | OCL-2.2V/330A |
| 4 × 18.5 kW74 kW · 152 A | ACS880-107-210A-3 | ACS880-R55-206A-3+SMM | OCL-2.2V/230A |
| 5 × 18.5 kW92.5 kW · 190 A | ACS880-107-250A-3 | ACS880-R63-246A-3+SMM | OCL-2.2V/250A |
| 10 × 11 kW110 kW · 230 A | ACS880-107-300A-3 | ACS880-R72-293A-3+SMM | OCL-2.2V/330A |
Source: project ABB–INOMAX comparison schedule, 25 May 2024. These are comparison-stage selections, not the final motor totals. Load values are summed motor nameplate ratings. Model pairings do not establish identical specifications or drop-in interchangeability; the application conditions require engineering review.
A Competitive Alternative to ABB for Industrial Drive Projects
The customer evaluated both the proposed drive configurations and commercial terms. INOMAX offered a substantially lower equipment price for the project while addressing the specified drive requirements. The decision also considered lead time, factory capability and operating references. Project pricing is assessed against the agreed configuration and supply scope.
CUSTOMER EVALUATION
Customer Evaluation
and Supplier Verification
INOMAX’s lower price and shorter lead time addressed the immediate project pressures. The customer travelled to China before committing, to see whether the capabilities and operating references supported the offer.
A more competitive project price
The ABB proposal was substantially more expensive. INOMAX’s lower offer directly addressed the end customer’s sensitivity to equipment cost.
Why it mattered
A better fit for the project’s purchasing budget.
A shorter delivery lead time
The project was urgent. INOMAX could offer a shorter lead time than the ABB option under consideration, making delivery a key part of the decision.
Why it mattered
An offer better aligned with the customer’s schedule.
Confidence built through visits
The customer assessed INOMAX’s factory and visited existing steel-plant installations in China before selecting the solution.
Why it mattered
Direct evidence of capability and equipment in operation.
BEFORE THE FINAL DECISION
From the factory floor
to an operating steel plant.
The visit allowed the customer to examine how INOMAX develops and manufactures its drives, and to see the equipment working in a demanding industrial application.
- 01
Assess R&D, production and quality assurance
At the INOMAX factory in China, the customer reviewed the company’s R&D strength, production processes and quality-assurance arrangements. The visit also covered INOMAX’s experience supplying alternatives to ABB and Siemens drives in other projects.
- 02
Visit the Shougang steel-plant installation
INOMAX took the customer to existing steel-plant projects in China, including an installation at Shougang in Beijing. There, the customer saw INOMAX drives operating well in a real steel production environment.
- 03
Choose after weighing the whole offer
With the factory capability and steel-plant operation assessed in person, the customer weighed technical suitability, price, lead time and the supplier’s project experience, then selected the INOMAX solution.
THE DECISION
Competitive pricing and faster availability made INOMAX worth considering. Factory assessment and operating references gave the customer the confidence to choose it.
06 / MANUFACTURING & SITE FEEDBACK
Manufacturing, Delivery
and Site Feedback
INOMAX manufactured the drive cabinets to the project electrical design, prepared the equipment for shipment and received installation photographs and positive feedback from the customer.
01
Cabinet manufacturing
Power modules, internal connections, busbars and local operator interfaces assembled into the engineered lineup.
02
Packing and shipment
Protective wrapping and export packaging prepared for the completed industrial drive cabinets.
03
Customer site feedback
Customer-supplied photographs document the cabinet system and steel rolling application in Indonesia.
Project photographs. Identifying customer markings in the site images have been masked. Select a photograph to enlarge it.
CUSTOMER-REPORTED OUTCOME
Delivered equipment.
Positive site feedback.
The customer shared photographs after delivery and expressed satisfaction with the project. Together with the engineering and manufacturing records, these materials document INOMAX’s supplied drive package. The regenerative system provides energy-recovery capability; actual site energy savings depend on the operating duty and system configuration.
07 / FREQUENTLY ASKED QUESTIONS
Regenerative Drive
Questions & Answers
Ten answers on energy recovery, DC-to-AC modernization, AFE technology, project scope and multi-motor drive engineering.
Can a four-quadrant regenerative VFD reduce energy consumption in a steel rolling mill?
A four-quadrant regenerative VFD can return eligible braking energy to the electrical supply during regenerative operating conditions. The actual energy savings depend on the motor load profile, braking frequency, operating cycle and system configuration.
Can INOMAX AC drives replace legacy DC motor drive systems?
INOMAX can evaluate DC-to-AC drive modernization projects based on motor specifications, mechanical requirements, speed and torque characteristics, control interfaces and the intended operating cycle. The replacement solution must be engineered for the specific application.
Is INOMAX a cost-effective alternative to ABB regenerative drives?
INOMAX provides project-specific industrial drive solutions for applications requiring regenerative operation and specialized motor control. In this Indonesian steel mill project, the customer evaluated both INOMAX and ABB proposals and selected INOMAX. Lower project pricing and shorter lead time were part of the decision, alongside factory assessment and operating references. Commercial comparisons depend on comparable equipment configurations, supply scopes and terms.
What is an Active Front End (AFE) drive, and why is it used in industrial drive systems?
An Active Front End (AFE) is an active power-conversion stage used between the AC supply and a drive system’s DC link. Depending on the system design, an AFE can provide controlled power conversion and support regenerative power flow back to the electrical supply. AFE selection depends on the application’s power-flow requirements, electrical network, harmonic requirements and overall system configuration. The INOMAX project documentation includes an AFE-based configuration for the steel mill roller conveyor drive system.
Did the customer compare INOMAX and ABB drive solutions?
Yes. During the project evaluation, the customer considered both ABB and INOMAX drive proposals and selected the INOMAX solution for the project scope. The evaluation involved motor-group configuration, drive selection, power conversion equipment, output reactors and overall electrical system arrangement. This page summarizes the approved technical selections; detailed commercial terms and confidential source documents are not disclosed.
Did INOMAX supply the motors and the entire steel mill production line?
No. The motors and associated equipment were sourced from an Italian supplier, while INOMAX supplied the drive system. INOMAX’s scope included drive configuration, project-specific electrical engineering, cabinet arrangement, manufacturing and delivery of the supplied drive equipment. Responsibilities for installation, commissioning and other site activities are governed by the project contract.
Can INOMAX provide customized VFD solutions for steel mills and roller conveyor systems?
INOMAX can evaluate project-specific drive requirements for steel mills, roller conveyors and other industrial motor control applications. The engineering process may include motor schedule review, drive sizing, multi-motor grouping, electrical topology, cabinet layout, output reactor selection and control interface definition. The final configuration depends on the motor data, operating requirements and agreed project scope.
What information is required to select a VFD for multiple motors?
For a multi-motor drive system, the engineering team typically needs:
- Motor quantity and rated power for each group
- Motor voltage, rated current, speed and type
- Required operating speed range and load characteristics
- Start/stop, forward/reverse and emergency-stop requirements
- Acceleration, deceleration and duty-cycle requirements
- Supply voltage, available fault level and installation conditions
- Required motor protection, communication and control interfaces
- Whether regenerative operation is required
These details help determine the appropriate drive rating, motor grouping, protection arrangement and cabinet configuration.
What documents can INOMAX provide for an industrial VFD project?
Depending on the agreed project scope, engineering documentation may include motor and drive schedules, electrical single-line diagrams, cabinet layout drawings, drive configuration lists, control I/O lists, connection diagrams and product technical documentation. For this steel mill project, the available materials include motor schedules, TR5 and TR6 cabinet layouts, electrical topology drawings and control interface information.
Does INOMAX have experience with large-scale industrial drive cabinet manufacturing and delivery?
This project provides a documented example of INOMAX manufacturing and delivering a multi-cabinet drive system for a steel mill roller conveyor application. Project records include cabinet layout drawings, photographs of manufactured equipment, internal cabinet components, export packaging and customer-shared site photographs. Industrial OEMs, system integrators and engineering contractors can contact INOMAX to discuss similar multi-motor VFD systems, high-power drive configurations and customized industrial drive requirements.
DISCUSS YOUR APPLICATION
Planning a DC-to-AC
or regenerative drive project?
Send INOMAX your motor specifications, operating cycle and existing drive arrangement to discuss a project-specific regenerative AC drive solution.