In the section below, you can find the most frequently asked questions (and answers) we received.
These are categorized in Operation, Reliability, Compliance, and Others.
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Capacitive loads can be found under many different forms: capacitor banks, batteries, and even power supplies themselves are considered as capacitive loads. The principal issue that can appear on such type of load is at PSU start-up: a discharged capacitor basically acts like a short-circuit at start-up, hence it may overload the output.
One solution is either to add current limiting resistors in series with the capacitive load to limit the output current, or to select a power supply with “constant current limiting” overload protection type. This way, the power supply will automatically limit the current to a certain level stated in the specifications:
![](https://meanwellpowersupplies.com/wp-content/uploads/2023/03/image-20.png)
SPV-150 series specifications
For inductive loads, motors need high current at start-up, therefore a power supply with peak power capability is recommended (or a PSU with constant current limiting overload protection type).
The main issue of dynamic loads is output voltage drop. If the load step is too high in amplitude and too long, it may be able to completely discharge the output capacitors and then create a voltage drop or high ripple at the output. If the frequency of the load changes is high enough, this kind of issue is less likely to happen (please refer to the test reports for more information). One solution could be to put additional capacitors between Power Supply and load.
Some applications may need to draw short peak currents from the power supply. If the PSU overload protection type is hiccup or constant current limiting mode, then it will not be able to provide the current peak needed by the load. Some of our power supplies come with a peak power capability that makes them suitable for these kinds of applications. (e.g. HRP-150N series)
![](https://meanwellpowersupplies.com/wp-content/uploads/2023/03/image-21.png)
For open-frame power supplies with peak capability, the user should refer to the derating curves, and check the thermal requirements (a fan may be required).
In general, there are two circumstances that will cause the power supply to shut down. The first one is the activation of the overload protection (OLP). To deal with this situation, we suggest increasing the rating of the output power or modifying the OLP point. The second one is the activation of over temperature protection (OTP) when the internal temperature reaches the pre-set value. All these conditions will let the Power Supply enter protection mode and shut down. After these conditions are removed, the Power Supply will be back to normal.
When current drawn exceeds the rating of the PSU, the protection circuit will be triggered to protect the unit against overload/overcurrent.
Protections of overload/overcurrent can be divided into several forms:
(1)FOLDBACK CURRENT LIMITING
Output current decreases about 20% of rated current, shown as curve (a) in the figure below.
(2)CONSTANT CURRENT LIMITING
Output current remains at a constant level and within the specified range while the output voltage drops to a lower level, shown as curve (b) in the figure below.
(3)OVER POWER LIMITING
Output power remains constant. As output load increases, output voltage decreases in proportion, shown as curve (c) in the figure below.
(4)HICCUP CURRENT LIMITING
Output voltage and current keep pulsing ON and OFF repeatedly when protection is activated. The unit automatically recovers when the faulty condition is removed.
(5)SHUT OFF
Output voltage and current are cut off when output load reaches protection range.
NOTE: Protection mode of some of the products combines with different types of the forms mentioned, such as constant current limiting + shut down.
![](https://meanwellpowersupplies.com/wp-content/uploads/2023/03/image-9.png)
Recover method:
(1)Auto Recovery: PSU recovers automatically after faulty condition is removed.
(2)Re-power on: PSU restarts by manual AC re-power on after faulty condition is removed.
Note: Please do not operate PSU in overcurrent or short-circuit condition for a long period of time to prevent a shorten lifespan or damaging the PSU.
MEAN WELL has launched ENC, HEP-600C, GC, PA, PB, RPB and RCB series for battery charge applications (30~1000W). However, if these models cannot fulfill your requirements, there is an alternative solution. Power supplies with constant current limiting as overload protection are suggested. Charge current varies in battery percentage (full or flat), there is high possibility to trigger overload protection when battery is low, those with overload protection as hiccup or shutdown will stop charging the battery in low battery condition. Yet, using a power supply as charging purpose is considered as overload usage, modification is required. Please Contact Us for the request.
1. To increase the reliability of the power supply, we suggest users choose a unit that has a rating of 30% more power than actual need. For example, if the system needs a 100W source, we suggest that users choose a power supply with 130W of output power or more. By doing this, you can effectively boost the reliability of the power supply in your system.
2. We also need to consider about ambient temperature of the power supply and whether there is additional device for dissipating the heat. If the power supply is working in a high temperature environment, we need to make some derating to the output power. The derating curve of “ambient temperature” versus “output power” can be found on our specifications.
3. Choosing functions based on your application:
- Protection function: Over Voltage Protection (OVP), Over Temperature Protection (OVP), Overload Protection (OLP), and etc.
- Application function: Signaling Function (Power Good, Power Fail), Remote Control, Remote Sensing, and etc.
- Special function: Power Factor Correction (PFC), Uninterruptible Power Supply (UPS) function.
4. Make sure that the model qualifies for the safety standards and EMC regulations you need.