When a power supply is first switched on, it momentarily draws a high peak current to charge its internal capacitors. This is the Inrush Current. If your circuit breaker isn't sized correctly to handle this brief pulse, it will trip immediately upon startup. To avoid this, you must match the MCB’s tripping characteristics with the PSU’s inrush profile.
Step-by-Step Selection Guide
If the specific circuit breaker count isn't listed in your PSU's installation manual, you can determine the correct unit by following these steps:
1. Gather Technical Data: Locate the following values in your PSU's datasheet:
- Inrush Current: The peak current (A) at startup.
- T50: The pulse duration (width) of the inrush current at 50% of its peak value.
- Rated AC Current: The continuous current draw during normal operation.
2. Use the Selection Tool: Access the MEAN WELL MCB Selection Tool.
3. Input Parameters: Enter your specific values into the tool.
4. On-Site Verification: Always verify the calculated results on-site, as local wiring impedance and environmental factors can influence the actual performance.
Example: HLG-600H
Let’s look at the HLG-600H series as an example (using 230VAC input):
- Inrush Current: 70A
- T50: 1000µs (1ms)
- AC Current: 3.3A
When these values are entered into the selection tool, the results provide the maximum number of units per breaker.
The following is a description of the classification of circuit breakers according to the tripping current characteristic curve:
|
Classification |
Tripping Current |
Applicable places |
| A | (2~3)*In | For protection of very sensitive circuits such as semiconductors. |
| B | (3~5)*In | Suitable for computers, electronic equipment and residential circuit protection. |
| C | (5~10)*In | For control circuits of general device, protection of illuminating circuits with high inrush current and all other supplementary circuits. |
| D | (10~20)*In | Protection for high inrush loads like transformers, solenoid valves, etc. |
The first column is the model of the circuit breaker, the first code is the classification of the circuit breaker, and the second code is the rated current. For example, B10 means B type with 10A rated current. The second column indicates the maximum number of HLG-600Hs that can be connected to one circuit breaker. For example, if B10 is selected, only one HLG-600H can be connected, and if D16 is selected, four HLG-600Hs can be connected.
Pro Tip: For most MEAN WELL power supplies, we recommend using MCBs with a "C" or "D" tripping characteristic. These curves are designed to tolerate higher surge currents before tripping, making them ideal for inductive and capacitive loads.
Note:
- MCB data adopts with ABB’s product, relevant data is only for reference. Different set-up may result difference.
- Please contact MEAN WELL technicians for product without T50 information.
- T50 is the time width of 50% of the inrush current value.
Application Scenario: Large-Scale LED Lighting
Imagine installing a stadium lighting system using 20*HLG-600H drivers. If you use standard "B-Type" breakers, you would need 20 separate breakers to avoid tripping during the initial power-up. By switching to "D-Type" breakers, you could consolidate the system to just 5 breakers (4 units each), significantly reducing cabinet space and installation costs.
If your system still trips despite using a D-curve breaker, consider adding an Inrush Current Limiter (ICL-16 series) to the circuit.
For details, please refer to the following technical article " Introduction and Selection: ICL-16 Series and Circuit Breakers "
https://www.meanwell.com/newsInfo.aspx?c=5&i=765
Conclusion
Choosing an MCB isn't just about the rated current; it’s about managing the "startup pulse." By using the T50 and Inrush current data, you can design a system that is both safe and cost-effective. When in doubt, always favor C or D curve breakers for industrial power applications.
If you have any technical issues, feel free to contact our team at contact@powersupplymall.com. We provide professional support and a wide range of power supply solutions.