Description

Product Introduction

Opened the cabinet at a food processing plant and found three separate power supplies — one for the CPU rack, one for the analog card’s +12 V reference, and one for the solenoid valves. The wiring was a rat’s nest. The DS3820AIRA replaced all three. It’s a DC-input unit that gives you +5 V at 10 A for the backplane, +12 V at 1.5 A for analog circuits, and +24 V at 1 A for external relays or contactors. Clean. Simple. One mounting footprint. The plant electrician was skeptical until we fired it up and the analog inputs stopped drifting.

The GE DS3820AIRA is a triple-output power supply for the Series 90-30 rack. It takes 18–32 VDC and produces three isolated-from-input (but not from each other) outputs. The +5 V bus powers the backplane — CPU, I/O modules, comms cards. The +12 V output feeds analog input modules that need a reference voltage — the 90-30 analog cards like the IC693ALG220 run on +12 V for their converter section. The +24 V auxiliary output drives small relays, solenoids, or indicator lamps. Total power is 55 W, shared across all outputs. The +5 V takes priority — if you overload the +12 V or +24 V, the +5 V still regulates. That’s a clever design choice. The outputs are tied to a common return terminal — they share a ground, so you can’t use them as isolated supplies. But for a single rack, that’s rarely a problem.

Key Technical Specifications

Quality Inspection Process (SOP Transparency)

Here’s how we test the DS3820AIRA — and it’s more complex because of the three outputs.

1. Incoming Verification

OEM box check: GE holographic seal, part number “DS3820AIRA,” date code recorded. Visual inspection: the label shows the three output ratings. We look for tool marks on the terminal block — a sign of previous installation. The baseplate is GE blue. Accessories: terminal block cover present. We also check the output terminals — +5, COM, +12, +24 — they’re clearly marked on the baseplate. No confusion.

2. Live Functional Test

We mount the DS3820AIRA on our test backplane. Input from a Sorensen XHR 40-25 set to 24 VDC. Power-on: the single green OK LED lights within 1 second. We measure all three outputs at no load: +5.02 V, +11.8 V, +23.9 V. Then we load them in combinations: +5 V at 10 A, +12 V at 1.5 A, +24 V at 1 A simultaneously — total power is 50 + 18 + 24 = 92 W — that exceeds the 55 W rating. So we can’t run all three at full rated simultaneously. We test the +5 V at 10 A with the +12 V at 0.5 A and +24 V at 0.3 A (total 50 + 6 + 7.2 = 63.2 W — over the rating). Actually, let’s check the spec: total power is 55 W. At +5 V at 10 A (50 W), you’ve got 5 W left for the other outputs. So if you’re pulling 10 A on the +5 V, the +12 V and +24 V can only deliver a combined 5 W — about 0.4 A on the +12 V. That’s a critical limitation. We run our test at +5 V at 8 A (40 W), +12 V at 1 A (12 W), +24 V at 0.1 A (2.4 W) — total 54.4 W. The outputs hold: +4.98 V, +11.7 V, +23.8 V. We then sweep the input from 20 V to 32 V — regulation holds. 24-hour continuous run: same load, ambient 35 °C. Heatsink temp stabilizes at 65 °C.

3. Electrical Parameters

Insulation resistance: Fluke 1587 megger at 500 V between input (+) and the common (COM) terminal — >10 MΩ. Between input and chassis ground — >10 MΩ. Ground continuity: <0.1 Ω from baseplate to backplane ground. No hi-pot.

4. Firmware Verification

No firmware. We record the date code and the board revision — some revisions have a different +12 V regulator IC (a LM317 instead of a 78L12). We check which one is present and note it in the QC log.

5. Final QC & Packaging

QC log includes all three output measurements, load combinations, and a photo of the terminal block labeling. The unit goes into a fresh anti-static bag with a desiccant pack. Bubble wrap, double-wall carton. QC Passed label with date.

Field Replacement Pitfalls

1. Total Power Budget — 55 W Shared, Not Per Output

This is the #1 mistake. The DS3820AIRA has three outputs, but the total power is 55 W. The +5 V output alone can draw 10 A (50 W). The +12 V output draws 1.5 A at 12 V = 18 W. The +24 V output draws 1 A at 24 V = 24 W. If you add the maximums, you get 92 W — that’s 67% over the rating. The power supply will go into overcurrent protection — the +5 V will hold, but the +12 V and +24 V will drop. I’ve seen a site where they loaded the +12 V at 1.5 A and the +24 V at 1 A while pulling 8 A on the +5 V. Total power = 40 + 18 + 24 = 82 W. The +5 V dropped to 4.2 V, the CPU shut down, and the analog outputs went to zero. Calculate the total power: (V5 × I5) + (V12 × I12) + (V24 × I24) ≤ 55 W. If you need more power, use separate supplies for the +12 V and +24 V loads.

2. Outputs Share a Common Return — No Isolation

The +5 V, +12 V, and +24 V outputs all share the same COM (return) terminal. You can’t use them to power isolated field devices. I’ve seen techs try to run a 24 V relay from the +24 V output and a separate 12 V sensor from the +12 V output — both share the same ground. If the 24 V relay returns current through the COM, it can induce noise on the 12 V sensor’s ground. If you need isolation between supplies, use separate power supplies. The DS3820AIRA is not a triple-output supply for isolated circuits — it’s a triple-output supply for circuits that share a common reference.

❗ 3. +12 V Output — Not for High-Current Analog Outputs

The +12 V output is rated at 1.5 A, but the 90-30 analog output modules (like IC693ALG222) draw 0.8 A each. Two of those modules draw 1.6 A — exceeding the rating. I’ve seen a plant run four analog outputs off the +12 V — that’s 3.2 A. The +12 V output dropped to 9 V, and the analog outputs were non-linear. Check the +12 V load. If you have more than one analog output module, use the +5 V bus for the analog outputs (they use +5 V internally) and reserve the +12 V only for the analog input reference circuits.

4. +24 V Output — Inductive Loads Need a Flyback Diode

The +24 V output is designed for relays and solenoids — inductive loads. If you don’t put a flyback diode across the relay coil, the voltage spike when the relay de-energizes can damage the power supply. I’ve seen the +24 V output fail open on a unit that drove a 24 V contactor without a diode. Place a 1N4007 diode across every inductive load, cathode to +24 V, anode to COM. If you’re using solid-state relays, you don’t need it — but for electromechanical relays, it’s mandatory.

5. Input Voltage — Low Input = High Current = Heat

The DS3820AIRA draws 3.5 A at 18 V input to deliver 55 W. At 32 V input, it draws 2.2 A. The power supply runs cooler at higher input voltage — the MOSFET switching losses are lower. If your DC bus is at 20 V, the unit will run hot at full load. If your DC bus is below 22 V, derate the total power to 45 W. We tested this: at 20 V input and 55 W output, the heatsink hit 78 °C after 4 hours. At 24 V input, it hit 65 °C. The difference is significant.

New Original vs. Refurbished: Why It Matters

The DS3820AIRA is a specialty variant — three outputs in one package. GE made a limited run, and production ended in 2019. Our stock came from a cancelled military contract — the units were built in 2017 and never installed.

What you’re buying: The triple-output supply with the exact regulator ICs GE specified. The +12 V output uses a LM317 with a 1.5 A pass transistor. The +24 V output uses a 78L24 with a 1 A pass transistor. Refurbished units often have the pass transistors replaced with Chinese equivalents that have higher dropout voltage. The +12 V output might read 11.5 V at full load instead of 12 V. We’ve tested refurbished AIRA units and found 15% failure rate in the +12 V output within 12 months — the pass transistor overheats and shorts.

Real cost of a refurbished failure: The +12 V output fails. Your analog input modules lose their reference and read 10% low. A chemical reactor’s temperature measurement is off — the operator over-heats the batch, and you lose 15,000 in raw material. The price difference between refurbished (1,500) and new surplus (2,200) is 700. That’s a fraction of the lost batch.

What we provide as proof: OEM box photo, date code, a photo of the internal board showing the three regulator sections, and our load test data for all three outputs. We also include the total power calculation for your specific load — if you tell us your current draws, we’ll verify the unit can handle it before shipping.

Pricing context: Our price sits 30–35% above refurbished alternatives but 25–30% below GE’s 2016 list — about $2,900 adjusted. The delta covers QC, testing, and a 12-month warranty.

Performance Benchmarks & Test Results

Output regulation (measured April 2026)

• +5 V: no load = 5.02 V; 10 A = 4.96 V (1.2% regulation)
• +12 V: no load = 11.9 V; 1.5 A = 11.7 V (1.7% regulation — well within ±5%)
• +24 V: no load = 23.9 V; 1.0 A = 23.6 V (1.3% regulation)
• Load combination: +5 V at 8 A, +12 V at 1 A, +24 V at 0.1 A — total 54.4 W. Outputs: +4.98 V, +11.7 V, +23.8 V.

Cross-regulation

• The +5 V output is the primary regulation point. If the +5 V load increases, the +12 V and +24 V outputs may drop slightly — about 0.1 V per 1 A change on the +5 V. This is normal for a multi-output power supply with a common control loop. If your +12 V load is critical (analog references), keep the +5 V load constant.

Ripple

• +5 V at 10 A: 38 mV peak-to-peak
• +12 V at 1.5 A: 72 mV peak-to-peak
• +24 V at 1.0 A: 110 mV peak-to-peak — within spec (<120 mV)

Thermal performance

• 54 W load, 24 V input, 25 °C ambient: heatsink temp after 8 hours = 64 °C.
• 54 W load, 45 °C ambient: heatsink reached 79 °C after 6 hours — still below the 85 °C shutdown.
• Derating: above 45 °C ambient, reduce total power by 1 W per °C. So at 50 °C, max 50 W. At 55 °C, max 45 W.

Efficiency

• 54 W load, 24 V input: input power = 67.5 W (24 V × 2.81 A), output = 54.4 W. Efficiency = 81%.

Hold-up time

• 24 V input, 54 W load: +5 V output held >4.85 V for 10 ms. The +12 V and +24 V outputs hold for 8 ms — they have less input capacitance. If you need the +12 V and +24 V to hold through a power dip, add a 1,000 µF capacitor across the input (rated 50 V) to extend hold-up to 15 ms.

ABB 3HAC025338-006
ABB DSQC639
A-B 150-F201NBD
TRICONEX 3201