Model 81D

Specs

  • Secondary: 8.25” x 34” winding length, 24AWG wire (same as 81G)
  • Topload: 34” x 8” corrugated drain pipe covered with foil tape (same as 81G)
  • Primary: 15T of 3/8” soft copper tubing, 3/8” edge-edge spacing (same as 81G)
  • Primary Capacitor: 5s16p CDE942C20P15K MMC, 0.48uF @10KVDC, 216A RMS, 6912A peak
  • Frequency: Secondary system is 70kHz, primary is detuned to roughly 65kHz (turn 4)
  • Bridge
    • Layout: H-bridge with voltage doubler for 680VDC with 240VAC input
    • IGBT: 2x Mitsubishi CM300DY-24H
    • Bus capacitor: 5500uF @ 900VDC. 2x CDE 520C 11000uF, 450VDC inverter-grade electrolytic in series. 15kOhm / 10W bleeder/balance resistors
    • Bus: Laminated, 1/16” aluminum, 1/16” G10/FR4 insulating layer
    • Rectifier: Semikron semipak SKKD81/16
    • Snubber: 2x Aerovox RBPS direct-mount, 2uF 1000VDC each
  • Driver: UD2.7C
  • Feedback/OCD: 50:20:1 current transformers, Fair-rite Type 77 (5977003801 and 5977006401)
  • Interrupter: Dual Channel MIDI Interrupter
  • OCD: Currently set to 800A. Could probably handle 1000A+
  • Arc length: ~7ft with ~200VAC input running ~45uS on-time while playing music.

Introduction

In early 2018, I was bit by the DRSSTC bug when it became apparent just how much heavy iron I had accumulated in my quest to bring my 15kVA Pole Pig powered SGTC online.

I already had a large heatsink salvaged from a 7kVA UPS system. I figured I could reconfigure my existing CDE 942C MMC to get one good for 0.48uF, 10kVDC 216A RMS. I simply needed a driver, bus caps, interrupter, IGBTs, laminated bus, gate drive transformer, and a few other odds and ends to construct the bridge.

This coil is based around a full bridge of CM300DY-24H modules, a voltage doubler arrangement for 5500uF @900VDC, Gao Guangyan’s UD 2.7 driver, and the same 8” secondary and 3/8” primary from the 8” SGTC”.

This coil saw first-light Sept 17 2019, and the first full-power run was conducted Sept 21 2019 without any issues whatsoever.

Construction

Bridge


MMC


Driver

The driver is Loneocean’s UD 2.7C, with the HFBR series ST fiber module installed.


Testing

Results of low-power testing were promising. Phase lead was adjusted for minimal ringing on the DC bus.

  • Yellow: Gate voltage
  • Cyan: Bus voltage
  • Magenta: Primary current

Videos

Low power

High power