13th March 2018


You will find handy product or series specific FAQ’s are featured within the product series description under the series image gallery. Below we have listed other FAQ’s that are not necessarily product or range specific for your attention.

Q. What is Power Boost?
A. Power boost is the reserve power that is available constantly of which allows reliable start up of loads with high inrush current.

Q. Why is Power Boost Beneficial?
A. Power Boost is especially useful for applications where loads are active; the high current can cause the power supply unit (PSU) output to dip down if the PSU does not have the capability to withstand this surge current. Consequently, this could reset the system and result in equipment downtime.

Q. What kinds of applications or environment need it?
A. For example, in an EV charging terminal, the power supply is powering all the controls and safety electronics. In such a system there could be up to ten DC/DC converters and POLs. Each converter has an inrush current and all DC/DC converters are connected in parallel. Therefore the total inrush current is the multiple of all the DC/DC converters. Delta’s Power Boost of 150% up to 5 seconds helps to reduce the need for active inrush limiters and/or avoid sequence power on.

Q. What should I consider when selecting a Power Supply Unit (PSU)
A. Efficiency and Reliability are the two most important factors to consider in selecting a PSU. The best way to ensure the reliability of the PSU is to choose one that provides a maximum of 30% more output than your actual total requirement. For example, if your system has a 90W power requirement, you should choose a PSU with at least 120W power output rating. By doing so, you are boosting the reliability of the PSU as well as prolonging the entire system life. An efficient PSU will thus ensure that power loss is minimised and will greatly help to lower your operating costs in the long run. By choosing a cheaper, but less efficient PSU will just mean that you are paying for it through your monthly electric bills. Delta’s CliQ Din-Rail Power Supply easily give our users a substantial efficiency of up to 87%.Other factors to consider include the operating conditions, types of safety certifications, PSU protection and application functions. Please contact your nearest Delta sales representative for a recommendation based on your requirements.

Q. Do you recommend the Output negative (- , Gnd) be tied to Earth Ground (PE/FG)?
A. No, this is not recommended. What we know from the Industrial PS background that it needs to have isolated gnd. In a complete system, there are many components such as VFDs, Servos, Motors, and Contactors which are all switching devices. They will generate a large amount of harmonics if the output ground is tied to FG then the noise from these would possibly get coupled with PS and if the PS is supplying the power to PLCs, Analog devices are susceptible to these noises.

Q. Is there any difference in the output power rating if the PSU is installed horizontally, rather than vertically?
A. Yes. There is a direct impact on the output power rating. We would recommend installing PSU in a vertical orientation to get better performance. More details can be found in your manual.

Q. What does MTBF mean?
A. MTBF means “Mean Time between Failures”. It is a indicator of reliability. Therefore, the higher the MTBF, the more reliable the product is.

Q. Why is important to know the “Inrush Current”?
A. Each time the power supply is turned on; there will be a large “Inrush Current”. This is the inherent property of all Switching Power Supplies. Depending on the design, the Inrush current is limited to 40A, 60A or 80A. It will return back to its normal current rating immediately. Although the inrush current is high it will not damage the supply as the internal components are designed to handle these large pulse currents but it is not advisable to switch On/Off the PS very frequently as this may cause the AC Source circuit breaker to get into protection mode due to large Pulse current.

Q. Will a 3-phase power supply still operate normally if there is only 2-phase power input?
A. Delta’s 3-phase power supply allows for a wide range of input operating voltages. This range from 320Vac to 575Vac with a nominal range of 400Vac to 500Vac. To operate normally, the power supply will require a minimum 2-phase input voltage of 360Vac unlike a minimum 320Vac for a 3-phase power supply. For higher powered models such as the 480W and above, the min 2-phase input voltage is 380Vac. In case the minimum input is lower than this, there will be a power derating. Please contact your nearest sales representative for more details.

Q. In order not to suffer power loss when operating at a higher ambient temperature, would you recommend using an additional fan to cool the power supply?
A. No. This is not recommended due to safety concerns.

Q. How much input surge voltage can a single-phase power supply withstands?
A. The maximum input surge voltage is 300Vac for 0.5 seconds.

Q. What is the power derating curve for side by side installation in a panel?
A. We do not recommend installing 2 power supplies side by side. Each power supply should maintain a minimum distance of 20mm from each other.

Q. Can you tell me the condition when the “DC OK” LED turns on? What are the conditions that will cause the LED to turn off?
A. The LED is directly connected across the output voltage (LED in series with current limiting resistor). The LED will turn ON as soon as the power supply is switched on. The LED will turn off under the following conditions:

  1. When the AC Supply is turned off or not present.
  2. The LED is faulty.
  3. The output voltage is faulty or not present

The LED light will be blinking when it is in the hiccup protection mode.

Q. Why is a range (rating) given (example: 6-16A) and can we use the fuse as the backup?
A. The range is given for the choice of power circuit-breaker to be used for different models. During the safety tests, Delta follows the recommended value advised by safety agencies i.e. 16A min. This is because during safety failure tests, we depend on the power supply fuse to blow rather than the power circuit-breaker to open. But if a lower value power circuit-breaker is used, the power circuit-breaker will trip before the fuse is open thus avoiding the field returns. Therefore we do not recommend using the fuse instead of the power circuit-breaker as the backup.

Q. What is the maximum input surge current the single-phase 240W and 480W can withstand?
A. 100A for the 240W single-phase power supply. 150A for the 480W single-phase power supply.

Q. How much input surge voltage can single-phase power supplies withstand?
A. The maximum input surge voltage is 300Vac for 0.5 seconds.

Q. What is the correct size of ORing Diode to be used to connect two power supplies in parallel?
A. Please refer to the manual for details on the ORing Diode and its connection.

Q. Does Delta’s power supply come with any IP or NEMA protection rating?
A. Currently, both Delta’s PMC and CliQ power supply are certified as Built-In Product hence they do not come with IP level protection. However, Delta will be introducing a new range of CliQ power supply with IP20 protection rating.

Q. What is Advanced Power Boost or APB?
A.Within a multiple loads connection, Advanced Power Boost (APB) can detect a faulty current path and provide a large outrush current to trip the circuit breaker connected to the faulty path. This prevents the system from shutting down while the other connected current paths continue to operate without interruption.