How sophisticated instrumentation helped a drone maker accelerate motor system testing

The Yokogawa WT1800E Power Analyzer is being used by Atmos UAV to optimise the range, efficiency and safety of Marlyn, the world’s first drone to combine Vertical Take Off and Landing (VTOL) and forward flight in a fully autonomous flight.

Like a fixed wing drone, Marlyn is capable of high-speed flight, which typically enables it to survey an area of 12 square kilometers in a single flight, while the VTOL capability allows it to be launched from almost anywhere. This superior flying performance means that surveyors can dramatically reduce the required flying time, and thus achieve higher productivity and lower operating costs.

Benefiting from the ability to operate safely and reliably in wind speeds up to 45 km/h, Marlyn is being used throughout the world to survey, map, and gather geospatial data in the mining, agriculture, forestry and construction industries, and by government agencies.

The challenge for Atmos was to select a combination of motor system and propeller which could provide the required thrust in-flight and during take-off and landing, while maintaining a flat and safe power dissipation profile across all the varying load conditions.

By using the Yokogawa WT1800E, Atmos was able to significantly reduce the time required to test combinations of off-the-shelf motors and propellers, and enabled them to find the optimal configurations with certainty quickly.

Previous attempts to measure motor/propeller combinations used readings from a temperature sensor as the basis to calculate power dissipation. This was a slow procedure and it was difficult to compare results. By utilising the WT1800E, which provides up to six measurement channels to enable electrical power measurements of up to six voltages and six currents at a sampling of rate of 2MS/s, Atmos was able to take measurements at the motor’s power supply, the motor drive circuit and at the motor simultaneously. These measurements were used to rapidly calculate power dissipation in the motor drive and the motor.

“We performed our first tests without using a power analyzer – it took over four hours to do a test for each single motor drive combination”, says Dirk Dokter, Technical Director & Founding Partner of Atmos, “with a power analyzer, the test time fell dramatically. After fine-tuning the power analyzer test set-up, the time to test a single motor fell to just 30 minutes.”

“The most important question with measurement equipment is: Can you trust the results it produces?”, Dirk emphasizes, “I did not have to worry about the WT1800E on this score – I had total confidence in the values displayed on screen. I know that the WT1800E was telling me the actual power dissipated.”

The WT1800E is a high-performance power analyzser which guarantees a power accuracy of 0.05% of reading, plus 0.05% of range. Unlike measuring instruments which are not designed to measure power as their primary function, the power measuring accuracy of the WT1800E is specified for all factors such as power factor, crest factor, phase angle error, temperature range, warm-up time, stability period and common mode rejection. The high levels of stability also mean that measurements are consistent when repeated over the lifetime of the instrument.

The WT1800E was developed to be flexible enough to provide engineers with accurate and reliable power measurements for applications as demanding as the manufacture of energy efficient devices and appliances, plug-in hybrid/electric vehicles, lighting, aircraft and for renewable energy technologies. With one to six channels and the capability to measure harmonics up to the 500th order, it is the perfect device for comparisons of the input and output of three-phase systems, such as motors, inverters, actuators, energy recovery systems and generators and other applications requiring multiple input channels.

Providing GP-IB, USB and Ethernet Modbus/TCP connections and a web server, the WT1800E also gives engineers a comprehensive tool for power analysis which may easily be integrated with design or production software tool suites.

Dirk adds, “The Marlyn design has exceeded our expectations in terms of reliability. That’s not just in normal operation – because of the results from our power dissipation testing, we know that we can produce more thrust without risk of the drive overheating. We have a safety margin over and above what’s required in normal operation. That’s very important for us, because our name is on the aircraft, and the Atmos brand stands for reliability and performance.”

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