How can reliable measurements be achieved in electric motor testing laboratories?
In electric motor testing laboratories, the quality of the electrical power supply is crucial to ensuring accurate test results. Harmonic distortion, high-frequency noise and transients generated by electronic power supplies can alter measurements, affecting the evaluation of the actual performance of the components under test.
To meet this requirement, IREM has developed a 150 kVA three-phase AC-AC linear power supply system, a Power Quality solution based on electromechanical technology that is completely free of power electronics.
The equipment uses a servo-controlled three-phase variable autotransformer with continuous regulation and a series transformer, eliminating at the source the harmonic distortion phenomena typical of inverter, PWM and double-conversion AC-DC-AC architectures. The result is an output voltage that preserves the harmonic profile of the utility supply without introducing additional disturbances.
Performance of the 150 kVA system
The system is supplied directly from a 400 V three-phase mains supply, with an operating frequency of 50–60 Hz, and provides continuous output voltage regulation from 4 V to 400 V.
The rated power is 150 kVA (433 A line current), while the regulation accuracy maintains the static error within ±0.5% of the set value.
A feedback control system continuously monitors the input voltage and automatically adjusts the autotransformer contact position, ensuring a stable RMS value even in the presence of mains fluctuations or load variations.
Why does an electromechanical architecture improve test quality?
The absence of electronic switching devices provides a waveform free from notches, ripple and high-frequency noise.
This enables laboratories to analyse exclusively the actual behaviour of the component under test, preventing the power supply from introducing errors into efficiency measurements, iron and copper loss evaluations, or the thermal behaviour of electric motors, inverters and their associated drives.
With the continuous increase in electric motor efficiency classes and the reduction of tolerances permitted in certification tests, access to a zero-distortion power supply is becoming an increasingly important requirement for obtaining reliable results.
Analog control and dynamic voltage stabilisation
Voltage regulation is managed through a remote interface with a standardised 0–10 VDC analogue signal, which drives a servomotor coupled to the autotransformer.
The system’s linear response replaces traditional manual or relay-based regulation while maintaining all the advantages of electromechanical technology and ensuring continuous, precise stabilisation of the output voltage.
Thermal stability and long-term reliability
The equipment is designed to ensure high reliability even under continuous-duty operation.
The windings use Class H insulating materials, while the conductor sizing is designed to operate within Class F limits, providing a thermal margin of approximately 25°C. This improves the ability to withstand overloads and transients while extending insulation service life.
Cooling is achieved exclusively by natural convection (AN method). The absence of cooling fans eliminates one of the main causes of failure, reduces routine maintenance, eliminates acoustic noise and increases the Mean Time Between Failures (MTBF).
Which design solutions improve safety?
The structure is manufactured from high-strength sheet steel with an IP21 degree of protection when the doors are closed.
During inspection activities, IP2X protection is ensured by transparent solid polycarbonate protective barriers that allow visual inspection of the internal components while maintaining protection against direct contact.
Applications in testing laboratories and industry
The system has been designed for all applications where electrical precision and reliability are fundamental requirements.
It is used in testing laboratories for electric motors, inverters and isolation transformers, in research and development centres dedicated to the certification of electromechanical components, in industrial production lines subject to unstable voltage conditions, and in the marine and railway sectors, where variable voltage and frequency power supplies are required.
In addition to providing an extremely clean power supply, the system eliminates measurement artefacts, reduces electromagnetic interference and maintains a stable output voltage even in the presence of fluctuations in the industrial power grid.
Scalability up to 1 MVA
The architecture developed by IREM is fully scalable and can be custom engineered.
The technology can be configured for single-phase and three-phase systems with voltages ranging from 110 V to 690 V and power ratings up to 1 MVA, adapting to the specific requirements of testing laboratories and industrial applications requiring the highest Power Quality standards.
