High Voltage Enclosure

This git repository contains all of the design files (both mechanical and electrical) as well as extensive documentation for the high voltage safety enclosure. It is meant to be living and not used simply as a reference. Any updates to the design should be uploaded to the repository, along with any necessary updates to the documentation files. Keeping these files up-to-date is important, especially since new high voltage enclosures or maintenance / part replacement on existing enclosures may require the files to be used again at any given time (unlike former research projects, which will be used as references but more likely than not will never be built again).

Note: Do NOT make a new commit to this repository while Solidworks is open!! Solidworks creates a bunch of temporary journal files and mod files while it is open which should not be committed to the repository.

Overview

The high voltage safety enclosure is an assembly designed to protect someone in the event of a catastrophic mechanical failure of a converter under test or improper use of electrical equipment during a test which would otherwise result in the possibility of the person touching something at high voltage. The enclosure consists of the following parts:

• A cover which can be lowered to cover a portion of the lab bench and raised to allow access to the test setup
• A latching mechanism which holds the cover in the raised position
• A button assembly which detects when the cover is open or closed and which drives the electrical components of the enclosure
• An HV Electrical Box which contains electronics to operate the high voltage contactors and bleeder resistors on the input side of the converter under test
• An Auxiliary HV Electrical Box which is an optional assembly containing electronics to operate bleeder resistors on the output side of the converter under test

The cover protects a person against catastrophic mechanical failure and against unintentional contact between a foreign object and the converter under test. The electrical boxes and button assembly ensure that the converter under test can only be energized (i.e. connected to the power supply) when the cover is down; when the cover is up, bleeder resistors are automatically connected across the input to bleed any large input capacitors that may be energized (and, if the auxiliary HV Electrical Box is used, bleeder resistors are automatically connected across the output to bleed any large output capacitors as well).

Repository Structure

The following is a guide to where various files and components are located in this repository.

• The mechanical folder contains all of the CAD models of nearly every component used in the mechanical portion of the HV enclosure. Since the enclosure was designed in Solidworks, all CAD files are .sldprt, .sldasm, or .step files. Notably, this folder does not include any bolts, nuts, or L brackets used in the cover, and does not include the gate latch used in the latching mechanism. Below is a list of the kinds of files that can be found here:
  • All 8020 beams used in the cover and electrical boxes
  • All acrylic pieces used in the cover and electrical boxes
  • 3D exported renderings of the various PCBs in the design
• The electrical folder contains all of the Altium component libraries, schematics, and layouts for the various PCBs designed for the HV enclosure. Below is a list of the PCBs used in the design:
  • Main Board: this board connects to the incoming 12 V DC supply from the wall, sends power to the other boards, operates the contactors, sends signals to operate the bleeder resistors, receives the signal from the button detecting when the cover is closed or not, and displays the state of the system to the user.
  • HV Board: this board connects the power supply and the converter under test. It contains the high-voltage JFETs that connect/disconnect the bleeder resistors across the input of the converter, as well as mounting holes for the contactors which electrically connect/disconnet the power supply from the converter under test.
  • Auxiliary HV Board: this board connects the converter under test with the load. It contains high-voltage JFETs that connect/disconnect the bleeder resistors across the output of the converter.
  • Button Board: this board houses the lever switch which detects when the cover is closed, which is sent to the Main Board.
• The production folder contains all of the files that will be uploaded to various supplier websites for custom fabrication:
  • The .STL file of the button board holder model
  • The .DXF files for all of the acrylic panels
  • The .DXF files for all of the aluminum heat sinks
  • The .ZIP files containing the gerbers for all of the PCBs
• The docs folder contains more documentation and useful reference material:
  • BOMs for the mechanical and electrical components used in the HV enclosure (as well as the suppliers and supplier links of those components)
  • What supplier manufacturing options were selected when ordering the parts for the HV enclosure
  • Assembly instructions for the HV enclosure
  • Documents describing what needed to be considered and what principles were followed throughout the design process
  • All photos and screenshots used in the repository

Quick Specifications

The following is a list of the most important specifications of the system as designed in the first prototype:

• Rated voltage: 1000 V
• Rated current (banana plugs): 25 A per plug
• Rated current (Phoenix connector): 75 A per pin
• Bleeder resistor value: 4x 390 Ohms in parallel (total 97.5 Ohms)
• Bleeder resistor power ratings: 100 W per resistor (continuous, with heat sink); 12.5x overload for 2 seconds
  • Maximum power dissipation is 5 kW for 2 seconds across entire resistor bank - appoximately enough to discharge 10 mF of input capacitance at 1000 V, reducing the voltage on the input bus below 100 V in a little over 2 seconds (see datasheet, page 3 "Power Overload" graph for details)

Credits

First prototype designed and assembled by Ben Liao in late 2023 to mid 2024 (completed August 2024). Contributors to this first iteration included Logan Horowitz, Nathan Biesterfeld, Nathan Miles Ellis, and Robert Pilawa. Original documentation written by Ben Liao.