What factors should I consider when selecting a power supply?

Consider load requirements, efficiency, power factor, and safety standards.

How do I calculate load requirements?

Sum the wattage of all connected devices and add a safety margin.

What safety standards should be met?

Ensure compliance with UL, CE, and IEC 60950 standards.

Why is efficiency important in power supplies?

Higher efficiency reduces energy consumption and operational costs.

How much headroom should I include when sizing an industrial power supply?

It is recommended to size industrial power supplies with 20-50% headroom above the peak load current. This additional capacity helps accommodate inrush currents, temperature derating, and transients, ensuring reliable operation in harsh environments.

What are the limitations of Class 2 power supplies under UL 1310?

Class 2 power supplies under UL 1310 are limited to a maximum output of 60 VDC/30 VAC and 5 A, with a total power output not exceeding 100 VA. These limitations are designed to minimize fire and electric shock risks, making them suitable for low-voltage industrial applications.

What insulation requirements must industrial power supplies meet for safety?

Industrial power supplies must meet specific insulation requirements such as basic insulation of 1500 VAC and a creepage distance of 4.0 mm, as outlined in IEC 60601-1 derivatives. These standards are critical for ensuring the safety of both patients and operators in medical-industrial hybrid environments.

What efficiency standards should be targeted for industrial power supplies?

For industrial power supplies, it is essential to target efficiency standards of greater than 90% as per IEC 62368-1. This high efficiency reduces heat generation and energy loss, which is crucial for maintaining performance and reliability in industrial settings.

What is the significance of IP ratings for power supplies in industrial environments?

IP ratings, as required by UL 508, indicate the level of protection provided by enclosures against dust and moisture. For industrial applications, power supplies should achieve IP67 ratings to ensure they can withstand dusty and wet conditions, enhancing durability and operational reliability.

Power Supply Selection for Industrial Systems — Knowledge Base

Q: What is power factor?

Power factor indicates how effectively the power supply converts electrical power into useful work.

Learn how to select the right power supply for industrial systems, considering factors like load requirements, efficiency, and safety standards.

Introduction to Power Supply Selection

Choosing the right power supply is crucial for the performance and reliability of industrial systems. A well-selected power supply ensures adequate voltage and current for equipment operation while meeting safety and efficiency standards. Industrial power supplies must be sized with 20-50% headroom above peak load current to handle inrush currents, temperature derating, and transients, ensuring reliability in harsh environments. This article will discuss key considerations for selecting power supplies in industrial applications.

Understanding Load Requirements

The first step in selecting a power supply is understanding the load requirements of the system. Calculate the total power consumption by summing the wattage of all connected devices. Ensure that the chosen power supply can provide at least 20-50% more capacity than the total load to accommodate inrush currents and future expansion. Additionally, consider the maximum output limits set by standards such as UL 1310, which restricts Class 2 power supplies to 60 VDC/30 VAC output and a maximum of 5 A to minimize fire and shock risks.

Efficiency and Power Factor

Efficiency is a critical factor in power supply selection, as it impacts energy consumption and operational costs. Look for power supplies with a high efficiency rating (above 85%) to minimize losses. Efficiency standards target >90% for industrial supplies under IEC 62368-1 to reduce heat and energy loss, with derating curves showing 20-30% capacity loss at 50°C ambient. Additionally, consider the power factor, which indicates how effectively the power supply converts electrical power into useful work. A power factor close to 1 is desirable, and active power factor correction (PFC) is recommended for improved efficiency.

Safety Standards and Certifications

Ensure that the power supply complies with relevant safety standards such as UL, CE, and IEC 60950. Compliance with these standards ensures that the equipment is safe to operate and reduces liability. Notably, IEC 62368-1 mandates hazard-based safety engineering, replacing IEC 60950-1, with dielectric strength tests up to 4000 VAC for double insulation in medical-industrial hybrids. Furthermore, UL 508 requires industrial control equipment, including power supplies, to pass enclosure integrity tests for IP ratings up to IP67 in dusty/wet industrial settings.

Table of Power Supply Selection Criteria

Criteria	Description
Load Requirements	Power consumption of connected devices, with a recommendation for 20-50% oversizing for reliability.
Efficiency	Ratio of output power to input power, targeting >90% efficiency under IEC 62368-1.
Power Factor	Effectiveness of power usage, with a preference for active PFC (>0.95).
Safety Standards	Compliance with industry regulations, including UL 508 and IEC 62368-1.

Conclusion

Selecting the appropriate power supply for industrial systems is essential for operational reliability and efficiency. By considering load requirements, efficiency, and safety standards, engineers can make informed decisions that enhance system performance. Manufacturer recommendations suggest prioritizing DIN-rail mounting and ensuring compliance with relevant standards like UL 508A for industrial control panels to ensure safe integration.

References & Citations

UL Solutions - Power Supply Testing and Certification — Official page detailing IEC 62368-1 and UL 508 paths for industrial compliance.
Industrial Power Supplies Guide - c3controls — White paper on industrial power supply selection, types, specs, and regulatory standards.
Understanding Codes and Standards - Eaton — Video overview of NEC, IEC, and IEEE standards for power systems design in industrial applications.
Power Supply Safety Standards - Volgen — Technical article on IEC 62368-1 and UL 508 safety standards for power supplies.
Power Supply Safety Standards - Bel Fuse — Technical paper on power supply safety marks, including UL 1310 and IEC 62368-1.

Power Supply Selection for Industrial Systems