MEAN WELL IRM-90-48ST Power Supply

What it is

The Mean Well IRM-90-48ST is a 90W, 48V encapsulated AC-DC module from the IRM-90 series. Unlike the open-frame LRS brick or a DIN-rail HDR, this is a potted "green power module" designed to be built into a board or panel: a sealed block with screw terminals, 80-305VAC universal input, and no fan. It sits in the middle of Mean Well's lineup — a step up from the little 5V IRM/IRM-bricks, below the slim DIN-rail HDR units and the PFC-equipped UHP supplies.

What it powers in a printer build

This is a 48V unit, so it is for the 48V rail, not the bed. In a Voron / Klipper / RatRig build that means feeding stepper drivers and motors that run at 48V (high-torque setups, fast travel moves, CoreXY toolhead steppers) through your control board or a dedicated 48V stepper supply input. It does not power a 24V bed heater or 24V electronics, and it does not power a 5V Raspberry Pi. If your printer is a standard 24V build, this is the wrong voltage — match it to a board and steppers actually specified for 48V.

At 1.88A / 90W it is sized for the stepper rail of a single machine, not a whole 350mm bed. Check your driver count and current draw before assuming it covers everything.

The honest wiring & safety story

This module has bare screw terminals carrying live mains on the AC side. There is no enclosure, no IEC inlet, no fuse, and no strain relief in the box — that is your job. To wire it safely you need to provide:

• An inline fuse on the AC input sized to the module, plus external protection appropriate to your mains.
• Proper mains-rated wire, ferrules on stranded conductors, and torque-checked screw terminals.
• Mechanical protection so nobody can touch the live terminals — this is a potted module, but the screw heads are exposed. Mount it where the AC side is enclosed or covered.

This is a Class II supply: double-insulated, so there is no protective-earth requirement on the output side the way an earthed metal-case LRS has. That does not make the mains side safe to touch — 80-305VAC is still lethal. If you are not comfortable terminating mains, this is not the part to learn on.

Why this form factor

Encapsulated IRM modules are chosen when you want the supply on or beside a PCB, sealed against dust and vibration, running silently with no fan to fail. The potting makes it more rugged than an open LRS and tolerant of the rough environment inside a moving printer. The trade-off versus a DIN-rail HDR is that it does not clip into a control cabinet — it bolts down by its mounting holes and you build the surrounding protection yourself.

Verified spec

• Power: 90.24W
• Output: 48VDC @ 1.88A (2.07A peak)
• Input: 80-305VAC universal, 47-63Hz (also 113-431VDC)
• Efficiency: ~93%
• No-load draw: <0.21W
• Size: 109 x 52 x 33.5mm (4.29 x 2.05 x 1.32in)
• Cooling: fanless, free-air convection
• Operating temp: -30 to +80C (derate above +50C)
• Protections: short circuit, overload, over-voltage
• Insulation: Class II, over-voltage category III
• Safety: UL/TUV/EN 62368-1, CB, CE, EAC; 3-year Mean Well warranty

Genuine Mean Well. On sale now while stock lasts.