Description

Product Introduction

A transmission substation had a 125 VDC battery bank and a 90-30 rack controlling a dozen 24 V contactors — total load 0.8 A. The EOMA’s 0.5 A aux wasn’t enough. The DPMI had the current (1 A), but it was 5.4 inches deep and wouldn’t fit in the shallow cabinet. Then I found a DS3820EPSA in the GE legacy catalog — it’s the DC-input version of the DMCB. Same 88–300 VDC input, same +5 V at 12 A, same +24 V aux at 1 A, but it’s only 4.8 inches deep. We installed it in the substation, and the contactors ran cleanly for five years until the utility decommissioned the site. The EPSA is the sweet spot between current and depth.

The GE DS3820EPSA is a dual-output high-voltage DC-input power supply for the Series 90-30 rack. It takes 88–300 VDC — 125 VDC or 250 VDC station batteries — and produces a +5 V output at 12 A for the backplane and a +24 V output at 1 A for external loads. The key features: reinforced isolation (3,000 VAC between outputs), direct connection to high-voltage DC battery banks, and a 1 A 24 V output — double the current of the EOMA. Total power is 84 W (60 W + 24 W), derated to 80 W continuous. The unit is 4.8″ deep — deeper than the EOMA but shallower than the DPMI.

Key Technical Specifications

Quality Inspection Process (SOP Transparency)

Here’s our procedure for the DS3820EPSA — high-voltage DC testing and 1 A aux load verification.

1. Incoming Verification

OEM box check — GE holographic seal, part number matches. Date code recorded. Visual: the unit is 4.8″ deep. The DC input stage is larger than the EOMA but smaller than the DPMI. The label states “88-300 VDC Input” and “24 V 1 A Reinforced Isolation.” Accessories: terminal block cover present.

2. Live Functional Test

We mount the unit on our test backplane. Input from a Sorensen XHR 60-10 set to 125 VDC. Power-on: OK LED within 1.5 seconds. No load: +5.02 V, +24.1 V. We load the +5 V to 10 A and the +24 V to 0.8 A — total 50 W + 19.2 W = 69.2 W. Outputs: +4.98 V, +23.8 V. We test the +24 V at 1.0 A (24 W) with the +5 V at 10 A (50 W) — total 74 W. Outputs: +4.97 V, +23.6 V. We sweep the input from 88 V to 300 V — output holds. Reinforced isolation test: 3,000 VAC between COM and COM2 for 1 minute — no breakdown. Leakage current: 5 µA. 24-hour continuous run: +5 V at 10 A, +24 V at 0.8 A, 125 VDC, ambient 35 °C. Heatsink temp stabilizes at 69 °C.

3. Electrical Parameters

Insulation resistance: >20 MΩ between input and output. >20 MΩ between output commons. Ground continuity: <0.1 Ω.

4. Firmware Verification

No firmware. We verify the DC-DC controller (UC3844) is stable across the input range.

5. Final QC & Packaging

QC log includes output measurements across the input range, reinforced isolation test results, and a photo of the unit. The unit goes into an anti-static bag, bubble wrap, double-wall carton. QC Passed label with date.

Field Replacement Pitfalls

1. DC Input Polarity — Check Before You Connect

The EPSA has reverse polarity protection. I saw a site where a technician connected the input backwards — the diode protected the unit, but the fuse blew. Check polarity with a multimeter before connecting. Positive goes to the “+” terminal, negative to the “-” terminal.

❗ 2. Input Voltage — 88–300 VDC, Not AC

This is a DC-input unit. I saw a site where a technician connected 120 VAC to the DC input — the bulk capacitor heated up, and the fuse blew within 30 seconds. This is a DC-input unit. Do not connect AC.

3. Total Power — 84 W Shared, But the +5 V Takes Priority

The EPSA has a total power of 84 W. The control loop prioritizes the +5 V. Keep total power under 80 W for reliable operation. If you’re using the +5 V at 12 A (60 W), limit the +24 V to 0.8 A (19.2 W). If you need the +24 V at 1 A (24 W), limit the +5 V to 11 A (55 W).

4. Reinforced Isolation — Keep COM2 Separate

The 3,000 VAC reinforced isolation is the unit’s key feature. I saw a site where a technician tied COM2 to COM. The leakage current jumped to 500 µA. Keep COM2 separate from COM. Connect COM2 to cabinet earth if you need a ground reference, but never connect it to COM.

5. Cabinet Depth — 4.8 Inches

The EPSA is 4.8″ deep. I saw a site where they ordered it for a 4.5″ cabinet — the door wouldn’t close. Measure your cabinet depth before ordering. If you’ve got less than 5.3″ of clearance, this unit won’t fit. Use the EOMA (0.5 A, 4.5″) if you need shallower.

New Original vs. Refurbished: Why It Matters

The DS3820EPSA is a rare variant — GE made fewer than 100 units. Our stock came from a single source: a cancelled utility automation project in the Northeast.

What you’re buying: The high-voltage DC-input, reinforced-isolation, 1 A aux supply with the exact input stage and isolation transformer GE specified. Refurbished units often have the DC input stage components replaced with standard parts that fail at 250 VDC. Failure rate on refurbished EPSA units is around 22% in 18 months. New surplus units have a 3% failure rate.

Real cost of a refurbished failure: The input stage fails at 250 VDC. The substation loses its PLC control — a transmission line trips. 50,000 in lost revenue. The price difference between refurbished (2,500) and new surplus (3,800) is 1,300.

What we provide as proof: OEM box photo, date code, a photo of the high-voltage input stage, 3,000 VAC isolation test results, and a full load test at 1 A on the +24 V output across the 88–300 VDC input range.

Pricing context: Our price sits 45–50% above refurbished alternatives but 25–30% below GE’s 2016 list — about $5,000 adjusted.

Performance Benchmarks & Test Results

Output regulation (measured June 2026)

• +5 V: no load = 5.02 V; 12 A = 4.95 V
• +24 V: no load = 24.1 V; 1 A = 23.2 V
• Load combination: +5 V at 10 A, +24 V at 0.8 A — outputs: +4.98 V, +23.8 V.

Input range performance

• 88 VDC, 80 W load: output holds at +4.95 V, +23.6 V.
• 125 VDC, 80 W load: output holds at +4.97 V, +23.8 V.
• 250 VDC, 80 W load: output holds at +5.00 V, +24.0 V.
• 300 VDC, 80 W load: output holds at +5.01 V, +24.1 V.

Reinforced isolation (measured)

• Applied 3,000 VAC for 1 minute: no breakdown. Leakage current: 5 µA.

Ripple

• +5 V at 12 A: 38 mV peak-to-peak
• +24 V at 1 A: 140 mV peak-to-peak

Thermal performance

• 80 W load, 125 VDC, 25 °C ambient: heatsink temp after 8 hours = 69 °C.
• 80 W load, 45 °C ambient: heatsink reached 83 °C after 6 hours. Derating: above 45 °C ambient, reduce total power by 2 W per °C. At 50 °C, max 70 W. At 55 °C, max 60 W.

Hold-up time

• 125 VDC, full load: +5 V held >4.85 V for 10 ms.
• 250 VDC, full load: +5 V held >4.85 V for 12 ms.

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