> 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/hardware-overview/electrical-design.md).

# Electrical Design

## High-Voltage Sub-Assemblies

### Inverter

{% content-ref url="/pages/vkF5dOp17tAW6mzueBcW" %}
[Half-Bridge](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/pcb-design/half-bridge.md)
{% endcontent-ref %}

{% content-ref url="/pages/WaH6CJMsZKg3jL63YO1o" %}
[Voltage Doubler](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/pcb-design/voltage-doubler.md)
{% endcontent-ref %}

### Primary Tank Circuit

{% content-ref url="/pages/w3GddkNvoA8whQXF08HO" %}
[MMC Bank](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/pcb-design/mmc-bank.md)
{% endcontent-ref %}

{% content-ref url="/pages/HZVgIEhCPZ7ZQ1TQnfPb" %}
[Primary Coil](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/primary-coil.md)
{% endcontent-ref %}

{% content-ref url="/pages/08L6W7ynq8aIXEHaYzXP" %}
[Busbar Periscope](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/busbar-periscope.md)
{% endcontent-ref %}

### Secondary Tank Circuit

{% content-ref url="/pages/OTbf8qSjg0rlJZ8serhJ" %}
[Secondary Coil](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/secondary-tank-circuit/secondary-coil.md)
{% endcontent-ref %}

{% content-ref url="/pages/Yv7oIoSUqa7fcNtbRu1c" %}
[Topload](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/secondary-tank-circuit/topload.md)
{% endcontent-ref %}

## Low-Voltage Sub-Assemblies

### Control

{% content-ref url="/pages/2fde1FKwRcpEKAJVKjEN" %}
[Motherboard](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/pcb-design/motherboard.md)
{% endcontent-ref %}

{% content-ref url="/pages/jEDjHaXjALQ2EIRSCjF4" %}
[Raspberry Pi](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/raspberry-pi.md)
{% endcontent-ref %}

### Driver

{% content-ref url="/pages/yOmlh3SQZHM0icEAe3Ko" %}
[GDT Driver](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/pcb-design/gdt-driver.md)
{% endcontent-ref %}

### Feedback

{% content-ref url="/pages/zYGPMFg1VZcDaZgnwAvO" %}
[Current Sense](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/pcb-design/current-sense.md)
{% endcontent-ref %}

## Grounding Diagram

The diagram below illustrates the *Emma Mk1* RF ground connection schema. The <mark style="color:$success;">green arrows</mark> show a potential path of the current impulse due to a primary coil arc strike, returning to RF ground. The Y-capacitor (`Y-cap`) AC-couples the negative rail of the DC bus to RF ground, completing the current loop and providing a safe discharge path.

{% hint style="danger" %}
It is important to use a **Y-capacitor** since they are designed to fail open. Using a different capacitor type can lead to a scenario where it fails shorted, creating an extremely dangerous DC path between the large, high-energy DC bus capacitance, $$C\_{bus}$$, and the negative inverter bus rail, $$V\_{BUS-}$$.
{% endhint %}

<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%2Ft5fxVa5QvjC6bfVDcvcc%2Fimage.png?alt=media&amp;token=57b1da12-6e5c-4130-8e7f-eb1b395a345b" alt=""><figcaption><p><em>Emma MK1</em> RF ground diagram</p></figcaption></figure></div>

### RF Ground Counterpoise

The *Emma Mk1* RF ground was connected to a counterpoise consisting of a 4.5 x 4.5 ft. (1.4 x 1.4 m) wire mesh via a 4 AWG braided copper cable (RV battery jumper cable) since it is run exclusively indoors:

<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%2FteC9NoDeFvvb8AxY96ey%2FIMG_0204.png?alt=media&amp;token=847a89d0-c31c-4270-b53c-25622b591120" alt="" width="375"><figcaption><p><em>Emma Mk1</em> wire mesh counterpoise</p></figcaption></figure></div>

### RF Ground Busbar

All subsystems requiring RF ground are tied together via a screw terminal busbar (see image below) secured to the [Ebox bottom platform](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/mechanical-design/ebox-assembly.md#f-ebox-bottom-platform).&#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%2FypL2ieC5IZsSgSdYFN80%2FIMG_0203.png?alt=media&amp;token=cfcf5635-7ef5-4363-bf89-372ea84d0adc" alt="" width="375"><figcaption><p><em>Emma Mk1</em> RF ground busbar</p></figcaption></figure></div>

### Secondary Coil and Strike Rail RF Ground Connection

Refer to the image below, *Emma Mk1 strike rail and secondary coil RF ground connections.*&#x20;

The [secondary coil](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/electrical-design/secondary-tank-circuit/secondary-coil.md) is connected to the [RF ground busbar](#rf-ground-busbar) via the grounding lug assembly (`B`). The grounding lug consists of a 3D-printed PETG block with an M4 threaded insert. The thin enamelled magnet wire of the secondary is soldered to the threaded insert.

The [strike rail](/mujoseph-docs/emma-mk1-drsstc/hardware-overview/mechanical-design/primary-coil-holder-assembly.md#a-strike-rail) is connected to the RF ground busbar via the strike rail grounding lug assembly (`A`), consisting of a 3D-printed PETG block and a metal M3 set screw.

<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%2F1qFSKpsIo2YLMRT9tRn9%2Fimage.png?alt=media&amp;token=97570f94-6557-4e57-bcac-084313629408" alt=""><figcaption><p><em>Emma Mk1</em> strike rail and secondary coil RF ground connections</p></figcaption></figure></div>

{% hint style="info" %}
The wire connecting the secondary coil ground lug (`B`) has since been replaced with a thicker, 6 AWG wire to provide a lower inductance path to RF ground.
{% endhint %}

## Additional Resources

1. [Kaizer Power Electronics-Grounding, circuit protection, and EMI](https://kaizerpowerelectronics.dk/tesla-coils/drsstc-design-guide/grounding-circuit-protection-and-emi/)&#x20;
2. [Altium-How to Use Class X and Class Y Safety Capacitors](https://resources.altium.com/p/how-use-class-x-and-class-y-safety-capacitors)