MEAN WELL RT-125B is an enclosed triple-output AC/DC switching power supply with +5 V, +12 V, -12 V outputs and a total rated output of 132 W. It uses free-air convection cooling and a power-on LED. Select the load on every channel together and observe the CH1 loading recommendation, total-power limit and derating conditions below.
Product Datasheet
Download MEAN WELL RT-125 Datasheet (PDF)
This combined G3 catalog includes the RT-125 section on PDF pages 50, 51. Refer to the complete mechanical drawings and notes when planning installation.
Outputs and Load Conditions
| Complete model |
RT-125B |
| Output configuration |
Three outputs sharing the COM terminal |
| Total rated output power |
132 W |
| CH1 |
+5 V; rated 12 A; current range 0–12 A; ripple/noise 80 mVp-p max.; voltage tolerance ±2%; line regulation ±0.5%; load regulation ±1%. |
| CH2 |
+12 V; rated 5 A; current range 0–6 A; ripple/noise 120 mVp-p max.; voltage tolerance +9/-5%; line regulation ±1%; load regulation ±3%. |
| CH3 |
-12 V; rated 1 A; current range 0–1 A; ripple/noise 120 mVp-p max.; voltage tolerance ±6%; line regulation ±1%; load regulation ±6%. |
| CH1 voltage adjustment |
4.75–5.5 V |
| Typical efficiency |
78% |
To meet the stated voltage tolerance, the datasheet recommends CH1 load greater than 15% of its rated current. For this model that is greater than 1.8 A. This is the catalog recommendation for voltage accuracy; a current range beginning at 0 A does not remove this condition. The other channels have the individual current ranges shown above, with no separate minimum-load recommendation specified for them.
Keep the combined output power within 132 W and each channel within its current range. The separate maximum channel currents are not a promise that all maxima can be drawn simultaneously. Apply any temperature and input-voltage derating as well.
Voltage tolerance includes setup tolerance, line regulation and load regulation. Line regulation is measured from low to high input line at rated load.
Load regulation is measured from 20% to 100% rated load on the channel under test, with the other outputs at 60% rated load.
Unless otherwise specified, parameters are measured at 230 VAC input, rated load and 25°C ambient. Ripple/noise is measured with 20 MHz bandwidth using a 12-inch twisted pair terminated with 0.1 µF and 47 µF capacitors in parallel.
Input and Start-up
| AC input |
88–132 VAC / 176–264 VAC, selected by the manual switch |
| DC input |
248–373 VDC |
| Input frequency |
47–63 Hz |
| Typical AC input current |
3 A at 115 VAC; 2 A at 230 VAC |
| Typical inrush current |
Cold start: 50 A at 230 VAC |
| Leakage current |
<2 mA at 240 VAC |
| Setup / rise time |
500 / 20 ms at 230 VAC; 1,200 / 30 ms at 115 VAC, at full load |
| Typical hold-up time |
25 ms at 230 VAC; 30 ms at 115 VAC, at full load |
| Input surge withstand |
300 VAC for 5 seconds without damage, as specified in the datasheet |
The 300 VAC / 5-second surge statement is a temporary withstand condition, not the continuous AC input rating.
Select the correct 115/230 V input range before operation. The two AC bands do not constitute automatic continuous 88–264 VAC input.
Setup time is measured at the first cold start. Switching the supply off and on very quickly may increase the setup time.
Protection and Operating Features
| Short-circuit protection |
Listed in the datasheet |
| Overload protection |
110–150% of rated output power; hiccup mode with automatic recovery after the fault condition is removed |
| Overvoltage protection |
CH1: 5.75–6.75 V; hiccup mode with automatic recovery after the fault condition is removed |
| Cooling |
Free air convection |
| Indication |
LED indicator for power on |
| Component feature |
105°C long-life electrolytic capacitors |
| Factory test |
100% full-load burn-in test |
The overload percentage is a protection threshold, not a timed peak-power rating or an extra continuous output allowance. The 105°C capacitor rating is not the allowed ambient temperature.
The manufacturer datasheet lists a 3-year warranty; coverage is subject to the applicable manufacturer warranty terms.
Operating Environment and Derating
| Working ambient temperature |
-25 to +70°C, subject to derating |
| Working humidity |
20–90% RH, non-condensing |
| Storage temperature / humidity |
-40 to +85°C; 10–95% RH |
| Temperature coefficient |
±0.03%/°C over 0–50°C on the +5 V output |
| Vibration test |
10–500 Hz, 5 G; 10 minutes per cycle; 60 minutes along each X, Y and Z axis |
| Ambient-temperature derating |
-25 to 40°C: 100% load; above 40°C derate along the plotted line to 50% at 70°C |
| Curve mounting orientation |
Vertical and horizontal |
| Input-voltage derating |
100% across the selected 88–132 VAC or 176–264 VAC band; at 60 Hz |
| Altitude derating |
Above 2,000 m: reduce the allowed ambient temperature by 3.5°C per additional 1,000 m for this fanless model |
The upper temperature limit does not mean full rated load is available at 70°C. Keep the convection airflow path clear and apply both temperature and input-voltage derating. Refer to the original curves when selecting operation between the shown points.
The altitude note supplies a temperature adjustment above 2,000 m; this datasheet does not give a maximum operating-altitude rating.
Dimensions, Mounting and Terminal Wiring
| Housing dimensions, L × W × H |
199 × 98 × 38 mm |
| Case drawing |
902A |
| Drawing tolerance |
±1 mm |
| Base threaded holes |
4-M3; 120 × 80 mm rectangular spacing |
| Side threaded holes |
3-M3; 157 mm horizontal span with 18 mm spacing between the right-hand pair; use the drawing for the third-hole offset |
| Flange holes / slots |
3.5 mm diameter or width as shown |
| Terminal pitch groups |
8.25 mm and 7 mm groups as dimensioned |
| Input terminals |
1 = AC/L; 2 = AC/N; 3 = FG (protective earth) |
| Output common |
7 = COM |
| CH1 terminal |
8 = +5 V |
| CH2 terminal |
6 = +12 V |
| CH3 terminal |
5 = -12 V |
| Unused terminal |
4 = NC; leave unconnected |
Output voltages above are referenced to COM. Observe the specified positive or negative polarity for each channel; connect protective earth to FG. Follow the model drawing for the complete hole positions and terminal layout.
The M3 callouts identify mounting threads, not supplied screw quantities. Thread insertion depth, terminal torque and wire gauge are not specified on these catalog pages; do not infer them from another series.
The catalog pages provide mounting and terminal dimensions but do not identify a dedicated cable, mating-connector, terminal-cover or bracket ordering code.
Safety, Insulation and EMC
| Safety approvals listed |
UL62368-1; TUV BS EN/EN62368-1; EAC TP TC 004; BIS IS13252 (Part 1): 2010 / IEC 60950-1:2005 |
| Dielectric withstand |
Input–output: 3 kVAC; input–FG: 2 kVAC; output–FG: 0.5 kVAC |
| Isolation resistance |
100 MΩ between input–output, input–FG and output–FG; tested at 500 VDC, 25°C and 70% RH |
| EMC emissions |
BS EN/EN55032 (CISPR32) Class B; BS EN/EN61000-3-2; BS EN/EN61000-3-3; EAC TP TC 020 |
| EMC immunity |
BS EN/EN61000-4-2, -3, -4, -5, -6, -8, -11; BS EN/EN55035; BS EN/EN61000-6-2 (BS EN/EN50082-2); heavy industry level; EAC TP TC 020 |
| MTBF, Telcordia SR-332 (Bellcore) |
2853.1 thousand hours minimum |
| MTBF, MIL-HDBK-217F |
373.6 thousand hours minimum at 25°C |
The approvals and compliance entries below are those printed in this datasheet revision. A component listing does not certify the completed end equipment.
The component EMC tests used a 360 × 360 mm metal plate, 1 mm thick. Final equipment must be checked again for compliance with the applicable EMC requirements.
The datasheet specifies harmonic-current testing at 85% load. Keep this condition with the BS EN/EN61000-3-2 reference.
Weight and Packing Reference
| Catalog packing reference per unit |
700 g (0.7 kg) |
| Carton reference |
20 units / 14 kg / 0.85 CUFT |
The per-unit value is the catalog PACKING reference, not a measured net mass or the actual shipping-parcel weight. Carton data is shown separately.
