To compare power supply efficiency at part load, ask for input and output power at the operating points your machine actually uses. A single published efficiency value is not a curve, and a machine that spends most of its time at a small control load cannot be evaluated only at rated output. Procurement needs a comparable duty-cycle evidence packet—not an extrapolated percentage.
Start with machine states, not a preferred power rating
List the states that have different auxiliary demand: controls awake before production, active handling, waiting for an upstream process, and any permitted standby state. Record the duration and real output demand of each. A motor or heater branch should not be casually counted as a load on the auxiliary supply just because it is in the same machine.
The useful question is: which documented supply performs adequately at those specific states? “Most efficient” is incomplete unless the compared input, load, ambient and measurement methods are comparable. Do not turn a tiny sample from one operating point into an overall ranking.
The LRS-150-12 is an evidence example, not a measured curve
The WEHO LRS-150 table identifies the 12V model at up to 12.5A and lists 87.5% in its efficiency row. The authentic photographed unit agrees on its nominal 12V12.5A output. Neither the adopted product-page row nor the approved sheet supplies a complete part-load efficiency curve. Therefore this article does not assign efficiencies to 10%,25%,50% or 75% load.
This distinction matters even when the table value looks precise. A percentage can identify a documented point or an entry to clarify with the supplier. It cannot provide a missing curve’s shape, low-load loss or standby consumption. Nor does the generic series name prove that every voltage variant has the same efficiency behavior.
Request a table that can be compared
For each relevant operating state, ask the supplier or qualified test team to identify the input condition, stabilized output voltage/current, true input power, output power, ambient condition and measurement uncertainty. Keep the delivered model and document revision on every record. Include low-load or standby behavior if those states materially affect the equipment’s operating time.
| Record field | Why procurement needs it |
|---|---|
| Full model and revision | Prevents mixing voltage variants or changed hardware. |
| Actual input condition | Separates supply comparisons taken on different AC conditions. |
| Output power and operating state | Connects the observation to the machine duty cycle. |
| Input power method | Clarifies what the efficiency calculation uses. |
| Temperature and stabilization | Distinguishes a comparable steady record from a transient observation. |
| Uncertainty and repeat count | Keeps small apparent differences from becoming unsupported claims. |
Efficiency at a defined point is output power divided by input power. For a DC output, the adopted voltage and current observations must correspond to that same point. Have qualified personnel choose suitable input-power instrumentation and safe test arrangements; ordinary current readings alone do not automatically establish true AC input power.
Weight energy by the real duty cycle
For a state lasting a known interval, input energy depends on its input power and duration. Add the state energies to understand a documented cycle. Do not take an unweighted average of percentages and call it the machine’s energy efficiency: different states may transfer very different amounts of energy.
If only one state has been measured, label the conclusion accordingly. If the standby architecture changes between designs, describe that change separately rather than attributing every difference to the power supply. A calculation example with hypothetical values may explain a method, but it is not a measurement of the pictured WEHO unit; this guide intentionally does not fabricate such a result.
Do not trade away electrical fit for a percentage
An efficiency comparison follows a successful fit check. Confirm the real voltage window, steady and changing demand, permitted input condition, protection behavior, environmental exposure and installation constraints. A promising percentage cannot fix an incorrect output voltage, unknown peak demand or unsuitable enclosure.
The pictured LRS-150-12 is a shallow enclosed chassis:159mm along the roof’s long axis,97mm across the terminal edge and 30mm from base to roof. Its mechanical drawing gives threaded equipment-plate fixing features; it is not a DIN-rail model. Avoid attaching it to a rail merely because nearby control components use rails.
Keep document conflicts visible
The actual photograph reads AC INPUT100–240VAC3.0A50/60Hz. The approved sheet and public page contain different input-range wording, including a public switched-input description that is not reflected by an invented switch on this source unit. Do not combine those statements into a new operating specification. Obtain the applicable supplied-revision instructions before acceptance; preserve the real nameplate as photographed.
Frequently asked questions
Can the published 87.5% be used at every load?
No part-load curve was adopted here. Treat it as the published table entry and request the applicable conditions and additional points.
Is choosing a larger supply always less efficient at a small load?
A general assumption is not a model comparison. Obtain comparable evidence at the real load and input, then consider the rest of the fit requirements.
What if the supplier has no part-load data?
Record that evidence gap. Agree a safe, qualified acceptance method or select a candidate with sufficient comparable data; do not substitute invented curve points.
Sources and boundaries
WEHO LRS-150 English product page, reviewed 8 October 2026; exact enterprise-drive LRS-150/主图.jpg and 细节.jpg; full approved LRS-150 specification and drawing. No efficiency measurement, product ranking or machine compatibility test is reported.
