Description

Product Introduction

The 125 VDC battery bank at a water pumping station was running the control panel, but the techs kept replacing the standard AC-input power supplies — they’d connect them to the DC bus, and they’d blow within a week. I opened the cabinet, looked at the space constraints, and found a DS3820EOMA in the spare parts bin. It’s a DC-input, reinforced-isolation supply that takes 88 to 300 VDC direct from the batteries — and it’s only 4.5 inches deep. We wired it to the battery bank, set the +24 V aux to run the telemetry sensors, and the pumping station ran for six years without a single power supply failure. The “EOMA” is the DC-input version of the EMMA.

The GE DS3820EOMA 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 0.5 A for external loads. The key features: reinforced isolation (3,000 VAC between outputs), direct connection to high-voltage DC battery banks, and a compact 4.5″ depth — the same as the standard AC-input DS3820 units. Total power is 72 W (60 W + 12 W), derated to 70 W continuous.

Key Technical Specifications

Quality Inspection Process (SOP Transparency)

Here’s our procedure for the DS3820EOMA — high-voltage DC testing and compact-depth verification.

1. Incoming Verification

OEM box check — GE holographic seal, part number matches. Date code recorded. Visual: the unit is 4.5″ deep — the same as standard DS3820 variants. The DC input stage has smaller components than the DPMI. The label states “88-300 VDC Input” and “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 0.4 A — total 59.6 W. Outputs: +4.98 V, +23.8 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 0.4 A, 125 VDC, ambient 35 °C. Heatsink temp stabilizes at 66 °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 showing the compact depth. 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 — The Diode Protects, But Don’t Test It

The EOMA has reverse polarity protection. I saw a site where a technician connected the input backwards — the diode clamped it, but the unit ran hot for 10 minutes before 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. 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.

4. Auxiliary Output is 0.5 A — It’s for Sensors and Low-Power Relays

The +24 V output is 0.5 A — 500 mA. I saw a site where they connected a 24 V contactor (400 mA) plus a relay (100 mA) — the output sagged to 22 V. The 0.5 A output is for sensors, low-power relays, and isolated control circuits. If you need more current, use the DPMI (0.5 A, 5.4″) or the DMCC (1.5 A, 5.6″) — they have larger transformers but higher current.

5. Cabinet Depth — 4.5 Inches, But Verify Clearance

The EOMA is 4.5″ deep. I saw a site where they ordered it for a 4.3″ cabinet — it still didn’t fit. Measure your cabinet depth before ordering. The 4.5″ depth requires at least 5.0″ of clearance for connectors and cable routing.

New Original vs. Refurbished: Why It Matters

The DS3820EOMA is a rare variant — GE made fewer than 150 units. Our stock came from a single source: a cancelled utility substation project in the Midwest.

What you’re buying: The compact high-voltage DC-input, reinforced-isolation 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 EOMA units is around 20% 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 distribution feeder trips. 25,000 in lost revenue. The price difference between refurbished (2,000) and new surplus (3,000) is 1,000.

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 across the 88–300 VDC input range.

Pricing context: Our price sits 40–45% above refurbished alternatives but 25–30% below GE’s 2016 list — about $4,000 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; 0.5 A = 23.4 V
• Load combination: +5 V at 10 A, +24 V at 0.4 A — outputs: +4.98 V, +23.8 V.

Input range performance

• 88 VDC, 70 W load: output holds at +4.95 V, +23.6 V.
• 125 VDC, 70 W load: output holds at +4.97 V, +23.8 V.
• 250 VDC, 70 W load: output holds at +5.00 V, +24.0 V.
• 300 VDC, 70 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 0.5 A: 95 mV peak-to-peak

Thermal performance

• 70 W load, 125 VDC, 25 °C ambient: heatsink temp after 8 hours = 66 °C.
• 70 W load, 45 °C ambient: heatsink reached 81 °C after 6 hours. Derating: above 45 °C ambient, reduce total power by 2 W per °C. At 50 °C, max 60 W. At 55 °C, max 50 W.

Hold-up time

• 125 VDC, full load: +5 V held >4.85 V for 10 ms — the DC input has less capacitance than AC-input units.
• 250 VDC, full load: +5 V held >4.85 V for 12 ms.

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