> For the complete documentation index, see [llms.txt](https://mujoseph.gitbook.io/mujoseph-docs/llms.txt). Markdown versions of documentation pages are available by appending `.md` to page URLs; this page is available as [Markdown](https://mujoseph.gitbook.io/mujoseph-docs/emma-mk1-drsstc/testing-and-evaluation.md).

# Testing and Evaluation

## Loaded Resonant Frequency Analysis

The loaded resonant frequency of the Emma Mk1 was measured digitally using the [resonant period capture buffer](/mujoseph-docs/emma-mk1-drsstc/drsstc_driver-firmware-overview/serial-interface.md#dump-resonant-period-capture-buffer-command).

### Operational Parameters

* Open loop frequency: 264 kHz
* Tracked frequency max deviation: +5%, -35%
* PRF frequency: 50 Hz
* PRF fn-time: 200 usec (1% DC)
* OCD limit: 300 A
* Lead time: 25 nsec
* PRF cycles: 100 (burst duration: 2 sec)
* IGBT MFG P/N: [FGA60N65SMD](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/pcb-design/half-bridge.md#igbt-fga60n65smd)
* Breakout: [configuration 1](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/secondary-tank-circuit/topload.md#configuration-1)
* Ground: 4.5' x 4.5' [wire mesh counterpoise](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design.md#rf-ground-counterpoise)

### Data Analysis

The resonant period capture dump was plotted using the [*DRSSTCToolbox*](/mujoseph-docs/emma-mk1-drsstc/drsstctoolbox.md) (see plots below). The <mark style="color:$danger;">red dashed</mark> horizontal lines plot the [max positive/negative tracked frequency deviations](/mujoseph-docs/emma-mk1-drsstc/drsstc_driver-firmware-overview/serial-interface.md#start-frequency-max-positive-negative-deviation) (e.g., +5%, -35%). The <mark style="color:$success;">green dashed</mark> horizontal line plots the requested [start/open-loop frequency](/mujoseph-docs/emma-mk1-drsstc/drsstc_driver-firmware-overview/serial-interface.md#start-frequency) (264 kHz). The <mark style="color:$info;">**black**</mark> dashed line plots the mean of the resonant period capture buffer.

<div><figure><img src="https://2297250131-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FzNHSl7dsTOS0XjlMXnIe%2Fuploads%2FZkTKZWOBDm8Mz4lJtaQc%2F1-4_run_trial2.png?alt=media&amp;token=d513dc2f-a35d-42f4-9258-c019567acee8" alt=""><figcaption><p>Resonant period capture dump trial 1</p></figcaption></figure> <figure><img src="https://2297250131-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FzNHSl7dsTOS0XjlMXnIe%2Fuploads%2F1Ghok6SXueLbYic0RJM0%2F1-4_run_trial1.png?alt=media&amp;token=565f8a42-9f35-4c2b-a70e-d2f1d9edccb6" alt=""><figcaption><p>Resonant period capture dump trial 2</p></figcaption></figure></div>

The *Emma Mk1* has a loaded resonant frequency of approximately $$232,\text{kHz}$$, with a standard deviation of $$\sigma \approx 5.5,\text{kHz}$$, during arc formation. Thus, the primary resonant circuit can be intentionally detuned to this frequency by increasing the primary coil inductance (i.e., increasing the number of turns) to increase power delivery to the [secondary tank circuit](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/secondary-tank-circuit.md) during arc formation.

Unfortunately, this cannot be done with the current [primary coil](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/primary-coil.md); see the[ proposed adjustments](#proposed-adjustments-and-optimizations-for-mk2) below.

## :thermometer:Inverter Thermal Analysis

The thermal performance of the [high-voltage sub-assembly](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design.md#high-voltage-sub-assemblies) PCBs was evaluated using an IR camera.

### Operational Parameters

* Open loop frequency: 264 kHz
* Tracked frequency max deviation: +5%, -25%
* PRF frequency: 200 Hz
* PRF on-time: 200 usec (4% DC)
* OCD limit: 800 A
* Lead time: 25 nsec
* PRF cycles: 2000 (burst duration: 10 sec)
* IGBT MFG P/N: [FGA60N65SMD](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/pcb-design/half-bridge.md#igbt-fga60n65smd)
* IGBT max junction temperature: 347 F (175 C)
* Breakout: [configuration 2](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/secondary-tank-circuit/topload.md#configuration-2-preferred)
* Ground: 4.5' x 4.5' [wire mesh counterpoise](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design.md#rf-ground-counterpoise)

### Test setup

The [Ebox](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/mechanical-design/ebox-assembly.md#overview) acrylic front panel was removed for the duration of the tests since acrylic is opaque to IR. A thermal imaging camera (`TOPDON TC004 Mini`) was used to monitor the pair of [*Half-Bridge*](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/pcb-design/half-bridge.md) PCBs and the [*Voltage Doubler*](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/pcb-design/voltage-doubler.md) PCB during an active burst (see below).

<div data-with-frame="true"><figure><img src="https://2297250131-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FzNHSl7dsTOS0XjlMXnIe%2Fuploads%2FhIsXOPupzdQKJDg6s0ZA%2FThermal%20camera%20setup.png?alt=media&amp;token=ca0e42f3-6224-493f-9e9b-8a550ef2a766" alt="" width="188"><figcaption><p><em>Emma Mk1</em> inverter thermal <br>analysis setup</p></figcaption></figure></div>

### Data Analysis

The image below shows a side-by-side of the thermal camera viewport (left) and a render of the target scene (right).&#x20;

<div data-with-frame="true"><figure><img src="https://2297250131-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FzNHSl7dsTOS0XjlMXnIe%2Fuploads%2FPONUQ4KkJ0n3E0TR0eJ6%2Fimage.png?alt=media&amp;token=10dd0bb2-4c4b-45e6-903d-422a9f441df6" alt=""><figcaption><p><em>Emma Mk1</em> inverter thermal analysis target designations</p></figcaption></figure></div>

The [IGBTs](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/pcb-design/half-bridge.md#igbt-fga60n65smd) `A-D` experienced the largest temperature rise within the primary current loop during the 10-second active burst. Results were as expected. The test is demonstrated in the video below:

{% embed url="<https://youtu.be/H2vvYyfKwKU?si=w7EW4uxAngmtj7MD>" %}
*Emma Mk1* IGBT thermal analysis video
{% endembed %}

The test was focused on IGBT `D` , since it represents the worst-case baseline. Being the furthest from the [muffin fan array](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/mechanical-design/ebox-assembly.md#active-cooling), it experiences the largest temperature rise among the IGBTs.

The thermal camera measures the surface temperature of the IGBT-heatsink combination; it is important to note that the junction (silicon die) temperature of the IGBT will be significantly higher than the reported IR temperature. Even so, IGBT `D` experienced a max temperature rise of about 155°F (68°C), which is well below the [max junction temperature](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/pcb-design/half-bridge.md#specifications) of 347°F (175°C).

Although the implemented active cooling can be considered sufficient, there is significant room for improvement.

### Additional Notes

Referring to the image above: *Emma Mk1 inverter thermal analysis target designations.*&#x20;

Target `E` is the [Capacitor Cradle pilot LED](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/mechanical-design/pcb-rack-assembly.md#capacitor-cradle-assembly).

Target `F` is the rectification diode pair, `D1` and `D2`, on the [Voltage Doubler](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/pcb-design/voltage-doubler.md) PCB. Referring to the video above (*Emma Mk1 IGBT thermal analysis*), the diodes experienced a pronounced temperature rise due the significant current flowing through them. As power is delivered to the [secondary circuit](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/secondary-tank-circuit.md) to sustain the arc, $$V\_{bus}$$ sags substantially (due to the undersized bus capacitance), requiring the mains input to restore the charge on the [bus capacitors](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/pcb-design/voltage-doubler.md#bus-capacitors-als70a362ke250) between PRF cycles.

## Proposed Adjustments and Optimizations for Mk2

* Optimize active cooling. Redesign [*Half-Bridge*](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/pcb-design/half-bridge.md) PCB to directly mate with a dedicated fan assembly to improve IGBT cooling. Re-design the [*MMC Bank*](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/pcb-design/mmc-bank.md) and [*Voltage Doubler*](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/pcb-design/voltage-doubler.md) PCBs to incorporate their own dedicated fan assembly.
* Redesign the [*Current Sense*](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/pcb-design/current-sense.md) PCB. Reduce the physical size substantially, remove the Ethernet interface, and instead mate with the [*Motherboard* ](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/pcb-design/motherboard.md)PCB via the `J6` [pin header](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/pcb-design/motherboard.md#current-sense-interface), allowing the *Current Sense* PCB to be housed within the [*Motherboard Enclosure*](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/mechanical-design/motherboard-assembly.md#motherboard-enclosure).
* Replace the Raspberry Pi 4B with a [Raspberry Pi Compute Module 5 (CM5)](https://www.raspberrypi.com/products/compute-module-5/?variant=cm5-104032). The CM5 PCB supports an external WIFI antenna out-of-the-box via the on-board U.FL connector. This will improve the RF performance substantially. A simple, inexpensive two-layer adapter board to interface the CM5 with the *Motherboard* PCB `J4` [header](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/pcb-design/motherboard.md#wireless-control-interface) can be fabricated or purchased.
* Ensure the primary coil has additional windings (i.e., greater than the minimum required to achieve the nominal resonant frequency of the secondary tank circuit, with a given MMC capacitance) to allow for intentional detuning of the primary tank circuit.
* Replace the voltage doubler topology for the inverter bus source with a bridgeless totem pole PFC (Power Factor Correction) converter [\[1\]](#references). The converter can be controlled using a secondary `STM32G474RE` and a fork of the [*DRSSTC\_Driver*](/mujoseph-docs/emma-mk1-drsstc/drsstc_driver-firmware-overview.md) firmware.

## Gallery

### Test Runs

[YouTube playlist](https://youtube.com/playlist?list=PLZGtKHhJn5iQ\&si=abTwr9UqHmu2Q8un)

{% embed url="<https://youtube.com/shorts/S0B3wtATwnc?si=zZjl7WrYhCWCx4xv>" %}
*Emma Mk1* 15-second burst
{% endembed %}

### Long Exposure Photos

<div><figure><img src="https://2297250131-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FzNHSl7dsTOS0XjlMXnIe%2Fuploads%2FZ5p4L3S4fNiJPM0OYMNb%2F4.png?alt=media&amp;token=01d021eb-1cdb-44f5-a928-27e7e83c22a8" alt=""><figcaption></figcaption></figure> <figure><img src="https://2297250131-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FzNHSl7dsTOS0XjlMXnIe%2Fuploads%2FxOQiVxdpemQH8Y0JZ3wR%2F6.png?alt=media&amp;token=ac371ceb-6353-4a5a-a872-4455090eb1d0" alt=""><figcaption></figcaption></figure> <figure><img src="https://2297250131-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FzNHSl7dsTOS0XjlMXnIe%2Fuploads%2FAUjfBJ8iBfeu8B0QhU6H%2FIMG_1349.png?alt=media&amp;token=01cc468b-6fd1-478d-85d1-e00656679764" alt=""><figcaption></figcaption></figure> <figure><img src="https://2297250131-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FzNHSl7dsTOS0XjlMXnIe%2Fuploads%2FBUbLTNh1LHWV2IXruynG%2FIMG_1354(2).png?alt=media&amp;token=2a2e85d2-fbc8-4907-983f-38963bfca492" alt=""><figcaption></figcaption></figure> <figure><img src="https://2297250131-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FzNHSl7dsTOS0XjlMXnIe%2Fuploads%2FcGrogVlfybYQZxFt8nAM%2FIMG_1354(3).png?alt=media&amp;token=67c67ab4-84c2-4742-9ed5-8f40eb52bdd6" alt=""><figcaption></figcaption></figure> <figure><img src="https://2297250131-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FzNHSl7dsTOS0XjlMXnIe%2Fuploads%2FloWKXzfa72LfRhAgOEdA%2FIMG_1359(1).png?alt=media&amp;token=277f3984-0d8b-47ce-b4df-c2c6ed31ec45" alt=""><figcaption></figcaption></figure> <figure><img src="https://2297250131-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FzNHSl7dsTOS0XjlMXnIe%2Fuploads%2FsbjJYk7jCt1v6c2efJpy%2FIMG_1362(2).png?alt=media&amp;token=1ec51a1a-6b9d-437b-91c7-0965d188a51b" alt=""><figcaption></figcaption></figure> <figure><img src="https://2297250131-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FzNHSl7dsTOS0XjlMXnIe%2Fuploads%2F6AFPFSaQJ22fQUJ3FdCQ%2FIMG_1362(3).png?alt=media&amp;token=06830903-7db5-435b-9d2c-e8d29567520c" alt=""><figcaption></figcaption></figure> <figure><img src="https://2297250131-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FzNHSl7dsTOS0XjlMXnIe%2Fuploads%2FqPkWDJUJ8iQZ9RINWvCk%2F1.png?alt=media&amp;token=ec093fd1-9549-459b-b2d1-b6fdcac9fec7" alt=""><figcaption></figcaption></figure> <figure><img src="https://2297250131-files.gitbook.io/~/files/v0/b/gitbook-x-prod.appspot.com/o/spaces%2FzNHSl7dsTOS0XjlMXnIe%2Fuploads%2FCp4uFo5WLfCv16m0El6w%2F3.png?alt=media&amp;token=df64010f-4a9c-498e-8b01-7d2bf039be52" alt=""><figcaption></figcaption></figure></div>

## References

1. [AN4539 - HRTIM Cookbook](https://www.st.com/resource/en/application_note/an4539-hrtim-cookbook-stmicroelectronics.pdf)