Rig Testing: Thermal Mechanical Cycling of Electromagnetic Propulsion

With the development of new propulsion technologies, our engineering test team has contributed to testing electromagnetic propulsion systems for thermomechanical loads. The team was tasked with building and commissioning a test rig capable of safely testing and validating the impact that high power loads have on the thermal mechanical properties of the electromagnetic propulsion system. To see how our team managed the task, check out this post! This article is aimed at breaking down the test purpose, test article, and test rig for high power cyclical loads.

The purpose of the thermomechanical load cycle testing is to:

·       Investigate the thermal mechanical impact of cyclical loads

·       Quantify the impact of cyclical loads on the magnetic flux at each coil

·       Thermally image the electromagnetic propulsion system for uneven distribution of heat and cooling.

Test Article

The test article is an electromagnetic propulsion systems consist of four groupings of three armature coils (known as poles), one field coil, and two liquid cooling plates. Each of the three armature coils with a given pole are fed high power alternating current (AC) that is 120 degrees out of phase (creating three phase (3Ph) AC). The field coil is provided with direct current (DC) that runs around the perimeter of the engine. Lastly, there are two liquid cooling plates on the engine, front and back.

The test rig was comprised of the following main components:

·       AC power source unit (PSU)

·       DC PSU

·       2-ton electric chiller

·       Pulse Width Modulation (PWM) generation:

o   Analog Discover 2 (for wave generation)

o   Four Elmo gold drum position controllers (3Ph output)

The AC PSU was used to supply power to the four Elmo gold drum position controllers. The Elmos receive AC power and convert to 3Ph AC power. Analog Discover 2 is connected to all four E lmo s as a means to provide a wave form for the 3Ph output. The waveform generation provides the engineering team with more control on amplitude and frequency for the 3Ph AC power. The 3Ph AC power is then provided to each of the four poles.

The DC PSU provided DC directly to the field coil as the required power can be dialed at the power supply with no conversion needed.

The chiller was used to provide a glycol/water mix to the two cooling plates within the electromagnetic propulsion systems. The cooling plates are connected in parallel to maximize the system's cooling capability. 

The engineering team built and commissioned the test rig to perform the intended tasks with all safety checks complete before installing the electromagnetic propulsion system within the rig. The commissioning involved all sensor and parameter checkouts, high power safety relays tested, PSU safety relay integration, waveform generation and control, and coolant loop leak checks. The engineering team controls all test conditions from a computer workstation with a variety of software for each major component.

The instrumentation used for the testing was center around thermal couples attached to various locations around the engine, thermal imagine cameras for the front and rear face, and flux probes perpendicular to front face of each coil, both armature and field.

Testing was devised to use a HiPot test before and after each group of 20 cycles as a means to validate the internal electric degradation.

Thermal cameras are used to locate and monitor any hot spots observed within the testing. The flux probes are used to validate any degradation within the coils ability to output flux throughout the testing. Visual inspections were done after each group of 20 cycles to inspect mechanical issues on the front and rear surface.

Future and further testing:

The engineering team conducted testing using a flat profile for injected current. Further and future testing could be focused on current injection that follows and expected flight profile. This would provide more real-world analysis of impact in the internal of the engine. Additionally, by placing infrastructure around the engine, like the tracks used for the final build, forces can be quantified and linked to further test criteria and knock it off temperatures.

Reach out if you are interested to know more on electromagnetic propulsion testing.