How to choose a DIN rail circuit breaker for MEAN WELL power supplies


In addition to its main function of providing power to terminal devices and systems, the power supply system must also ensure safety during operation. As a rule, for each type of load, according to safety requirements, it is necessary to install one circuit breaker (or simply “automatic”), which opens the power supply circuit when the specified consumption current is exceeded by a multiple. However, for a task involving several power supplies, increasing the circuit breakers, one for each power supply, leads to an increase in the cost and number of the switches themselves and, as a result, unreasonable consumption of free space in the mounting plate or cabinet. A clear example would be an LED lighting system with multiple independent AC/DC power supplies.

Accordingly, in practice, the question often arises - how to optimize the number of circuit breakers depending on the number of subsequent power supplies, their total current consumption and starting currents. To facilitate this calculation, MEAN WELL offers several ways to determine the number of power supplies connected to one circuit breaker (miniature circuit breaker, MCB) of various types. In its calculations, the manufacturer relies on the following classification of types of AC circuit breakers:

Breaker type Breaking current Application
A (2…3)*I H For protecting very sensitive circuits, such as semiconductor circuits
B (3…5)*I H Applicable for computer equipment, electronic equipment and household circuits
C (5…10)*I H For control circuits, lighting with high starting current and other related circuits
D (10…20)*I H Protection for loads with high inrush currents like transformers, solenoids, motors , etc.

Where I H is the rated current.

Types B, C and D are recommended for use with MEAN WELL power supplies. Note: All calculations for the number of circuit breakers are based on ABB product specifications.

The easiest way to determine the number of AC / DC converters for circuit breakers of an acceptable type is to look in the Installation (Mounting) Instructions for a series of power supplies (if available, it is given on the product page, it can be both in Russian and in English) from the manufacturer. For example, for DIN rail power supplies of all SDR series , the number of power supplies will differ for each of the series:

Number of power supplies of the SDR series for circuit breakers of types C and D

The second way to determine the number of AC / DC converters for a circuit breaker of various types and ratings is to use the online calculator on the manufacturer's website. For example, according to the documentation for HDR-100 series DIN rail power supplies, the calculation will look like this:

Online calculator for the number of power supplies for circuit breakers

The number of power supplies per circuit breaker is determined on the basis of three parameters - inrush current, measured in amperes, at a supply voltage of 230V (AC); consumption current (AC Current), also in amperes, at the same voltage; and the duration of half the inrush current pulse (Twidth or T50, measured value, given in the documentation), in microseconds:

The duration of the half-pulse of the inrush current

For some types of power supplies such as AC / DC, for example, LED series, the calculation of the number of power supplies that can be connected to one circuit breaker of a certain type has already been calculated, and this information is in the Specification. For example, for the popular ELG-150 series, it is allowed to connect up to 3 power supplies per type B circuit breaker, or up to 6 power supplies per type C circuit breaker. Also in the Specification there is data for an online calculator with which you can determine the number of units for other types of circuit breakers:

Determination of parameters from the Specification for the ELG-150 series

In some cases, the information given in the Specification for the AC/DC converter series may not be complete for the online calculator - there may be no information on the duration of the half-pulse of the inrush current. In this case, it is advisable to additionally use the Test Report, which the manufacturer issues for each model in the series. For example, for the HDR-100-24 model, for the inrush current, both the nominal value (it must be used for calculation) and the actually measured value are given, and the result of measuring the duration of half the inrush current pulse is given:

Defining parameters for the online calculator from the Test Report

Thus, there are several ways to determine the number of power supplies that can be connected to different types of circuit breakers without exceeding their load capacity, thereby ensuring the creation of an optimal and reliable power supply system.

For questions related to the selection and use of MEAN WELL products, please contact .