SELECTION COMPARISON
Overview
These three series are the most commonly used power supplies of MEAN WELL in industrial situations. The difference is first of all in the mounting format: LRS is a closed metal case power supply that needs to be fixed with screws; NDR and SDR are DIN rail power supplies that are directly stuck on the rail.
The second is positioning: NDR is a conventional economical type among rail power supplies, while SDR goes one step further in terms of efficiency and functionality (built-in active PFC).
When selecting a model, first determine the installation method, and then determine the power and voltage.
reference table
| Comparison point | LRS | NDR | SDR |
|---|---|---|---|
| mounting | Screw-fastened, closed housing | DIN rail snap-on | DIN rail snap-on |
| typical scenarios | Installation inside equipment and chassis | Standard configuration in control cabinet | In the control cabinet, there are requirements for efficiency |
| construction features | Ultra-thin closed type, high cost performance | Standard guide rail structure | Rail structure, built-in active PFC |
| common power range | 35–1200W | 75–480W | 75–960W |
| selection focus | cost and size | Easy installation and versatility | Efficiency, reliability, harmonic control |
How to Decide
- First look at the installation location - if there are guide rails in the control cabinet, choose NDR or SDR directly; for fixed installation in the internal space of the equipment, choose LRS.
- Then calculate the power requirement - add the rated power of all loads and leave a headroom (generally recommended is 20%–30%, more for inductive loads or starting shocks).
- Confirm the output voltage - 24V is commonly used in industrial control, but there are also 12V and 48V applications, which must be confirmed according to the actual load.
- Determine whether higher efficiency or harmonic control is required - SDR will be given priority when power grid quality requirements are high or there are requirements for harmonic control.
- Environmental conditions - high temperature, dust or vibration environments require additional confirmation of the operating temperature range and protection requirements.
Why is power headroom important?
Long-term operation of the power supply at full rated power will significantly shorten its life and increase heat generation.
Leaving a headroom is not only a reliability consideration, but also leaves room for additional load later.
It should be noted that the instantaneous current of some loads (such as contactor coil pull-in, motor starting, capacitive load) is much larger than the steady-state current.
When selecting based on steady-state power only, power protection may occur at startup.
If you are not sure about the actual load situation, you can send us the load list to help estimate the required power and model.
Frequently Asked Questions
Can LRS be mounted on rails?
The LRS itself is a closed structure fixed with screws. If rail installation is required, an adapter is usually required. If the cabinet is mainly installed on rails, it is more appropriate to directly choose NDR or SDR.
Can two power supplies be connected in parallel to increase power?
Some series support parallel connection, but you need to confirm whether the specific model has this function and connect according to the official instructions. It cannot be assumed that any model can be connected in parallel.
What do the numbers in the part number represent?
MEAN WELL is generally named "series + power + output voltage", for example, LRS-350-24 means LRS series, 350W level, 24V output. However, some series have structural or functional suffixes, which need to be confirmed by the complete part number.
How much power should I choose?
Add up all load powers and leave a headroom, and consider the inrush current at the start-up moment. The specific load list can be provided and we will help calculate it.
Need help confirming a part number or application?
Send the complete part number, BOM, nameplate or product photos. Documents and images can be shared through WhatsApp, Telegram or WeChat.
