OmronC500-PS221-ESYSMAC C500 Rack Power Supply Unit, 100-120 / 200-240 V AC In, 5 V DC 7 A and 26 V DC 0.8 A Out

Product Description

What this part is

This is the power supply unit for an Omron SYSMAC C500 programmable controller rack. It occupies the leftmost position on the C500 CPU backplane and converts mains AC into the regulated low-voltage DC rails that the CPU, the backplane and every I/O unit in the rack run from. It is not a CPU, not an I/O module and not a standalone bench supply: without a C500 backplane it does nothing, and the C500 rack will not run without it.

Decoding the part numbers

C500 — the SYSMAC C500 mid-range PLC platform. PS — power supply. 221 — the rating/model within the range. -E — the export/CE-market build with the wide selectable mains input.3G2A5-PS221P-E and 3G2A5-PS221-E are Omron’s older internal designations for the same unit. Both appear on cartons and in machine documentation of this era, and either number will get you here. Omron used the 3G2A5 prefix across the C500 range before the C500-prefixed catalogue numbers took over, so a machine drawing calling for a 3G2A5-PS221-E is calling for this part.

Published specifications

Function: rack / backplane power supply unit for SYSMAC C500Input: 100–120 / 200–240 V AC selectable, 50/60 Hz — the range shown on this unit’s rating plateInput power: approximately 150 VAOutput: 5 V DC at 7 A and 26 V DC at 0.8 A (26 V rail commonly quoted as 24 V DC on some data sheets)Mounting: plugs onto and screws into the leftmost slot of a C500 CPU backplane; no separate DIN rail or panel mountingFront-face indication: POWER LED, plus the AC input and earth terminal block behind the terminal coverManufacturer status: discontinued and out of production; alternate designation 3G2A5-PS221-E

What these specs mean in practice

The number that matters when you are configuring a rack is not the 7 A headline but the current left over. Roughly 2 A of the 5 V budget is consumed by the C500 CPU and the backplane itself, which leaves in the order of 5 A on the 5 V rail for the I/O units. Add up the 5 V consumption of every input, output, analogue and special I/O unit you intend to fit and keep the total under that figure; a rack that boots but drops out intermittently under load, or throws random I/O faults, is very often an overloaded rack supply rather than a failing module. The 26 V rail is the small auxiliary supply and is easy to overrun if several units draw from it.

Check the voltage-selection arrangement on the unit against your incoming supply before applying power. Applying 230 V to a supply strapped for 115 V is the classic way to destroy one of these.

Quantity and configuration

One power supply unit, as photographed. This is the power supply only.

What is not included

C500 CPU unit, backplane/base rack, expansion racks, I/O units, memory unit or memory cassette, battery, programming console, connecting cables, terminal-block screws beyond those fitted, terminal cover if not visible in the photographs, and manual. If you are rebuilding a C500 rack from parts, budget separately for the backplane and the CPU — those are the expensive and scarce items, not the supply.

Installation and setup notes

Power down and isolate before removing or fitting; the unit is hot-swap-hostile and pulling it live will drop the whole rack. Confirm the mains selection strapping, torque the AC and earth terminals properly, and land a genuine protective earth — the C500’s noise immunity depends on it. On a rack that has been standing for years, expect the CPU’s own memory-backup battery to be flat regardless of the condition of this supply; that battery is a separate part and is not included.

Interchange guidance

Interchangeable with other C500-PS221-E / 3G2A5-PS221-E units. Not interchangeable with the CV500-PS221, which serves the entirely different CV-series backplane despite the similar number — a common and expensive mix-up. Other C500 supply variants in the range differ in input voltage and output current and are related models, not equivalents: check both the input range and the 5 V/26 V figures against the rack’s requirement before substituting. There is no modern drop-in replacement; C500 racks are maintained from used and new-old-stock parts, which is what this is.