INOMAX ACS580 & ACS880 – Motor Test Bench & Dynamometer Solutions

High-Performance Regenerative VFDs for Engine, Chassis, E-Drive & Powertrain Testing

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Overview

Motor test benches and dynamometer systems are the foundation of modern powertrain development, electric vehicle validation, and industrial motor manufacturing. Whether testing a 1.5 kW servo motor for a CNC machine or a 5 MW traction motor for an electric bus, the quality of test results depends entirely on the precision, responsiveness, and energy efficiency of the drive system.

At Inomax Technology, we supply ACS580 (general purpose) and ACS880 (high-performance) variable frequency drives to test bench builders, system integrators, and end users worldwide. Our drives are engineered for demanding dynamometer applications: four‑quadrant regenerative operation, Direct Torque Control (DTC) with sub‑5 ms torque response, full torque at zero speed, ultra‑low harmonic AFE (THDi <5%), and common DC bus multidrive architectures.

We are also actively expanding our global partner network. If you are a distributor, system integrator, or project contractor serving the motor test bench industry, we invite you to explore a partnership with INOMAX – factory‑direct pricing, technical support, market protection, and proven technology trusted by industry leaders including AVL, ZF, Huawei, Magtrol, Power Test and Taylor Dynamometer.

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Why Motor Test Benches Need High-Performance VFDs

Four‑Quadrant Operation – The Foundation

A complete test bench must operate in all four quadrants of the torque-speed plane:

• Quadrant I (Forward motoring) – Motor under test accelerates forward

• Quadrant II (Forward generating) – Load motor brakes the MUT, recovering energy

• Quadrant III (Reverse motoring) – MUT accelerates in reverse

• Quadrant IV (Reverse generating) – Load motor brakes the MUT in reverse

Our ACS880 AFE drives are true four‑quadrant regenerative systems, providing two‑way consistent loading capacity for different steering power mechanical tests. The torque response speed of the electric dynamometer reaches the millisecond level, making it ideal for simulated load and new energy industry applications.

Energy Waste – The Hidden Cost of Traditional Test Benches

Traditional DC dynamometer systems or non‑regenerative AC drives use resistors to dissipate braking energy as heat. For a 200 kW test bench running continuously, this wastes over 1.5 million kWh annually – enough to power 150 homes. The heat also requires expensive cooling infrastructure.

Our regenerative AFE solution returns >95% of braking energy to the grid, significantly reducing test energy consumption and realistically recreating the vehicle’s energy management scenario.

Precision Requirements – From Cogging Torque to Efficiency Mapping

Different test types demand different performance characteristics:

Harmonic Interference – Protecting Sensitive Measurement Equipment

Motor test benches are filled with sensitive instrumentation: torque transducers, power analyzers, oscilloscopes, and temperature sensors. High harmonic distortion from standard 6-pulse drives (THDi 40-80%) can corrupt measurements and damage sensitive equipment.

Our AFE drives maintain THDi <5% at 80-100% load, ensuring clean power for accurate measurements without external filters.

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Key Technologies – Professional Solutions for Test Bench Applications

1. Four‑Quadrant Regenerative AFE (Active Front End)

The ACS880 AFE uses IGBT-based active rectification instead of passive diodes, shaping the input current waveform to be sinusoidal and in phase with the voltage. When the load motor operates in generating mode (braking), the AFE returns >95% of the mechanical energy to the grid.

Technical benefits:

• THDi <5% at 80-100% load – Eliminates harmonic interference; meets IEEE 519 without external filters

• Unity power factor (>0.99) – Reduces utility penalties; maximizes transformer utilization

• Regenerative energy recovery – Returns >95% of braking energy to the grid; typical savings of 80-90% vs. resistor-based systems

• Constant DC bus voltage – Immune to grid fluctuations common in industrial environments

For back-to-back test bench configurations (MUT and load motor on a common DC bus), the AFE only needs to handle the net power difference, not the full circulating power – dramatically reducing the required input power rating.

2. Direct Torque Control (DTC) – Precision Under All Conditions

ACS880 DTC technology updates the motor model 40,000 times per second, delivering instantaneous torque response without an encoder for most applications.

Why DTC matters for test benches:

• Full torque at zero speed – 200% torque at 0 Hz; essential for locked‑rotor tests and cogging torque measurement

• Torque response <5 ms – Critical for dynamic load simulation and transient response testing

• Speed accuracy ±0.01% with encoder – Precise speed regulation for efficiency mapping

• Wide speed range – Rated torque from zero speed to 5-6× field weakening; one drive for creep to overspeed testing

• No encoder needed for most applications – Higher reliability; fewer failure points

3. Common DC Bus – Energy Sharing Between Motors

In a back-to-back test bench configuration, two motors are coupled together – one acts as the motor under test (MUT), the other as the load motor. With a common DC bus, the load motor’s regenerated energy flows directly to the MUT, with only the net power difference coming from the grid.

Benefits:

• Reduces required input power by 50% or more

• Virtually eliminates energy waste

• Smaller AFE rectifier – lower capital cost

• Multiple inverter modules can share one AFE

4. Master‑Slave Torque Control for Coupled Test Benches

For test benches with two motors coaxially coupled, our master‑slave torque control ensures perfect coordination:

• Master drive operates in speed control (typically the load motor)

• Slave drive operates in torque control, receiving torque reference from master

• Result – Seamless transition between motoring and generating modes; precise load simulation

• Redundant master capability – If master fails, slave can automatically assume master role

5. High Overload Capacity – Handling Peak Test Demands

Motor testing often requires short-duration peak torque conditions:

• Locked‑rotor testing – 150-200% torque at zero speed

• Overload testing – 150-200% torque for 60 seconds

• Impact/reversal testing – Rapid torque reversals for dynamic testing

Our drives deliver:

• ACS880 – 200% torque for 60 seconds, 250% for 30 seconds (ACS890 multi-module)

• ACS580 – 150% for 60s (constant torque), 120% for 60s (variable torque)

6. Wide Speed Range – One Drive for All Tests

From creep speed (0.1 RPM) to overspeed (120% of rated), our drives deliver full torque across an exceptionally wide range:

• Open loop (sensorless) – Rated torque from 0.5 Hz; speed accuracy ±0.5%

• Closed loop (with encoder) – Full torque from 0 Hz; speed accuracy ±0.01%

• Field weakening – Full power up to 5-6× base speed

This means one drive handles low-speed cogging torque measurement, rated speed efficiency mapping, and overspeed testing – eliminating the need for multiple drive configurations.

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Test Bench System Architectures We Support

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Test Types Supported – Complete Coverage

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Technical Specifications – Professional Grade

ACS580 Series (Cost‑Effective for Smaller Test Benches)

ACS880 Series (High‑Performance for Professional Test Benches)

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Real Projects – Proof of Performance

Our drives are already specified and used by world‑leading test bench manufacturers and end users. These projects demonstrate the performance and reliability you can offer to your customers.

Case highlights:

• AVL – Our ACS880 AFE drives power engine, chassis and electric drive test benches globally, delivering <5 ms torque response and >95% energy recovery.

• ZF – Used for motor and transmission testing with precise torque control across wide speed ranges.

• Huawei – Validated EV drive motor performance including temperature rise, overload, field weakening and efficiency mapping.

• Magtrol / Power Test / Taylor Dynamometer – Standard drive platform for their dynamometer systems.

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For Distributors, System Integrators & Project Contractors

Why Partner with INOMAX?

Partnership Models

Distributor Support Program

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Frequently Asked Questions

For End Users (Technical)

Q1: How much energy can a regenerative AFE drive save on a motor test bench?

For a 200 kW test bench operating 4,000 hours/year with 80% energy recovery and $0.12/kWh electricity, annual savings exceed $20,000. The mechanical energy generated by the prime mover is converted into electrical energy and fed back to the grid, providing significant energy saving effect.

Q2: What is the torque response time of ACS880?

<5 ms from zero to rated torque in open loop (without encoder). This is critical for dynamic load simulation and transient response testing.

Q3: Can ACS880 control both induction motors and permanent magnet motors?

Yes. ACS880 is a universal drive supporting both asynchronous induction motors and permanent magnet synchronous motors (PMSM), including dedicated MTPA and field‑weakening control algorithms.

Q4: What is the maximum output frequency for high‑speed motor testing?

500 Hz standard (30,000 RPM for a 2-pole motor). Extended options up to 1,200 Hz (72,000 RPM) and specialized solutions up to 3,200 Hz available.

Q5: Does the AFE drive require external harmonic filters?

No. The AFE maintains THDi <5% at 80-100% load without external filters, meeting IEEE 519 requirements.

For Distributors & Partners (Commercial)

Q6: What is the minimum order quantity (MOQ) for distributors?

No strict MOQ for initial orders. Volume discounts apply from 10 units per order. For OEM/private label, MOQ is negotiated.

Q7: What is the standard warranty period?

2 years from date of manufacture or 12 months from commissioning, whichever comes first. Extended warranty up to 5 years available.

Q8: What is your typical lead time?

Popular models (≤250 kW) – 3-5 working days from our China factory + shipping. Larger units (250-6,000 kW) – 2-4 weeks.

Q9: Do you offer market protection?

Yes. Exclusive territory agreements (subject to minimum commitment) and project registration. Registered projects are protected – we will not quote directly or work with other distributors.

Q10: Can you customize drives for my OEM requirements?

Yes: private labeling, custom parameter presets, special enclosures, modified firmware, custom voltage/frequency ranges.

Q11: What technical support can I expect for my customers?

Free pre-sales support: drive sizing, harmonic analysis, configuration recommendations. Post-sales: remote diagnostics (free), on-site commissioning (fee-based). Product training for your technical staff.

Q12: How does INOMAX compare to ABB, Siemens or Danfoss?

We are legitimate competitors. Our ACS880 uses the same Direct Torque Control (DTC) technology as ABB ACS880. Performance specifications match or exceed competition. Price is 20-30% lower. Lead times are shorter. Customization is more flexible.

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Ready to Partner with INOMAX?

Join a growing network of distributors and system integrators who have discovered that INOMAX delivers premium performance at a competitive price – with real factory support.

Apply for distributorship today:

• Fill out the form below with your company information and market focus

• We will contact you within 24 hours to discuss partnership terms

• Receive distributor pricing, marketing materials, and technical documentation