How to Use and Benefit from Power Supplies with Peak Power Capability

As industries advance and automation becomes more prevalent, DC motors have become increasingly integral to both household and industrial applications. These DC motors are commonly used in devices like electric doors, robotic arms, coffee machines, pumps, ATMs, and large printers. However, powering such DC motors or inductive loads—especially during startup—requires power supplies with sufficient peak power capability to deliver very high currents, sometimes several times above their rated output.

Common Approaches to Managing High Inrush Currents

Several strategies exist for accommodating these temporary power surges:

1. Using Higher Rated Power Supplies
   A typical solution is to use an oversized power supply—for example, using a 200W AC-DC converter to power a 100W DC motor with a 200% startup current. While effective, this leads to unnecessary costs and increased physical size.
2. Parallel multiple Power Supply Units
   Connecting multiple power supplies in parallel can provide the needed startup power. However, this approach raises the cost and consumes space. Note: Power supplies with “current sharing” capability are essential when using this configuration.
3. System-Level Optimization
   Implementing a sequential startup for DC motors can effectively lower a system’s peak current demand. While this method is cost-efficient, it may negatively impact the system performance, especially in applications that require multiple DC motors to start simultaneously and demand peak power capability from the power source.
4. Incorporating Buffer Modules or Supercapacitors
   Short-term peak current needs can be handled using supercapacitors or buffer modules, such as those in MEAN WELL’s DBUF Serie (DBUF20 and DBUF40), to supplement the main power supply during startup.

A Better Solution: Power Supplies with built-in Peak Power Capability

Rather than using workaround methods, a more efficient solution is a power supply that can deliver both continuous output and handle short-term peak demands. To meet this requirement, MEAN WELL offers the LRS-N2 and HRP-N3 series. These AC-DC converters provide short-duration peak power—up to 350% for 5 seconds—without the need for oversizing or additional components.

Product Overview

Model: LRS-100N2

Available voltages: 12V / 24V / 36V / 48V

Key Features:

• Delivers up to 200% peak power
• Wide AC input range: 85–264V
• Full protection: Overload, Overvoltage, Overtemperature
• Compact, low-profile design
• Dual certification: UL/EN62368-1 & EN61558-1
• Over Voltage Category III (OVC III)

Models: HRP(G)-N3 Series (HRP-150N3, HRP-300N3, HRP-600N3, HRPG-1000N3)

Available voltages: 12V / 24V / 36V / 48V

Key Features:

• Provides up to 350% peak power for 5 seconds
• Wide input range: 85–264V AC
• Full protection: Overload, Overvoltage, Overtemperature
• Wide operating range: -40℃ to 70℃
• Certified for altitudes up to 5000m
• UL/EN62368-1 recognized/certified
• 5 years warranty

Guidelines for Using Peak Power Models

To safely use these peak power models, observe the following:

• Average Power Output (P_av) should not exceed the rated power (Prated).
• Peak Duration (t): must be ≤ 5 seconds.
• Duty Cycle:    *100%  ≤ 35%

Power Selection Example

Application: 24V DC motor for a ticket printer
Input range: 200Vac – 240Vac
Peak Current Requirement: 12A (288W)
Non-Peak Current Requirement: 1A (24W)
Peak Duration: <3 seconds, max 30% duty cycle

Step 1: Identify candidates based on needed power: HRP-150N3-24 and HRP-300N3-24,
Step 2: Evaluate the smallest suitable unit (e.g., HRP-150N3-24) using peak power formula.

According to application’s conditions, we can get

• V_in = 200-240Vac
• P_pk = 288 W
• t = 3 sec
• T = 10 sec
• P_npk = 24 W
• Duty cycle = 30%
• P_rated = 156W (from the MEAN WELL HRP-N3 product specification)

STEP 3: Verify if the conditions for peak power for HRPG-150N3-24 are met.

1. Confirm the maximum peak power based on the HRP-150N3 specification is sufficient:
   Since V_in = 200-240Vac, the maximum duty cycle = 30%, and required peak power is 288W; based on below diagram; the required P_pk can pass spec peak power requirement.
   
2. Confirm if the maximum peak power width (t) is met:
   t= 3 sec < 5 sec: Pass peak power requirement specification.
3. Confirm if the duty cycles is within the specification:
   Max Duty cycle = 30% < 35%: Pass peak power requirement specification.
4. Confirm if the average power P_av is met (see formula above):
   Calculate if P_av < P_rated (156W)
   P_av = (288*3 + 24*(10-3)) / 10 = 103.2 W
   P_av < P_rated : Pass peak power requirement specification

Conclusion

HRP-150N3-24 is recommended for economical cost and compact size if the input voltage stays >200V AC. In case a full input range  of 100VAC-240VAC would have been needed; the HRP-300N3-24 would be the right solution.

Examples of applications which require peak power

Robotic Arms

Robotic systems require due to the internal DC motors high torque at startup. The HRP(G)-N3 series supports a 350% power peak for 5 seconds, eliminating the need for oversized power supplies while meeting transient power needs.

Large Format Printers

Large industrial printers draw minimal power during operation but require high peak power exceeding 2000W during roller startup. The HRP-1000N3 meets this demand without resorting to bulkier solutions.

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