Key Considerations in Sizing Inverters for Industrial Loads
Inverters are commonly used in industrial and infrastructure projects to convert DC power sources into usable AC power, enabling operation of equipment that requires 230Vac or 400Vac supply when only a DC input is available. These inverters are typically deployed as part of UPS-type systems and are essential for powering loads from battery banks, DC-UPS systems, fuel cells or solar-charged DC busbars.
Common applications include railway signalling systems, telecommunications infrastructure, utility networks, mobile power systems and in-vehicle power conversion. In these environments, inverters must support a mix of inductive, resistive and electronic loads, often in challenging conditions with limited access for maintenance.
Note: This article does not cover grid-tied inverters used in solar PV export systems or renewable energy generation. Powerbox Australia does not supply or support grid-tied inverter platforms.
We’ve compiled this handy guide as a starting point for choosing the right inverter for your industrial application. It highlights several key factors to consider, but isn’t intended to cover every scenario. For help with detailed system design or application-specific requirements, contact a Powerbox Sales Engineer for further advice.
1. Understand Load Type and Electrical Behaviour
Correct sizing begins with a clear understanding of the electrical characteristics of the load. Not all loads behave the same:
- Resistive loads such as heaters or incandescent lamps are predictable and easy to support. They draw a constant current directly proportional to their rated power.
- Inductive loads such as motors, solenoids or compressors exhibit high inrush currents at startup—often 5 to 10 times the nominal full-load current. These surges may last for several seconds depending on the load and its control method (e.g. direct-on-line vs soft start).
- Capacitive loads such as LED drivers, switch-mode power supplies or large DC-DC converters can draw a significant instantaneous peak current during initial capacitor charging.
Example: A 1.5kW blower motor with DOL starting may require an inverter capable of delivering over 6kW for 2–3 seconds. Failing to size for this results in overload shutdown or poor power quality during start-up.
2. Evaluate Surge and Peak Power Requirements
Inverters are typically rated for both:
• Continuous power output (e.g. 2000W), and
• Surge power handling (e.g. 3000W for 5 seconds).
Many industrial loads demand significant short-term peak power, especially when multiple devices start simultaneously or during abnormal load transitions.
When reviewing inverter options:
• Check surge rating (e.g. 150% of nominal for 5–10 seconds)
• Understand the crest factor supported (important for pulse loads)
• Consider coordination with external contactors, soft starters or sequencing to reduce demand
Example: A site using two air-conditioning compressors starting concurrently may require 2x the normal surge handling capacity if startup delay logic isn’t used.
3. Duty Cycle and Operational Profile
The duty cycle of the load affects how the inverter will thermally perform over time:
- If the inverter is running continuously at or near rated power, allow for thermal derating and conservative headroom.
- For intermittent operation, such as timed pump cycles or event-based actuation, a smaller inverter may suffice—provided the internal thermal limits are not exceeded.
Refer to manufacturer temperature rise curves and operating profiles, particularly when mounting in confined spaces or sealed enclosures.
4. Temperature, Altitude and Environmental Conditions
All inverter power ratings are based on standard ambient conditions (typically 25°C and sea-level altitude). Real-world industrial environments often exceed these conditions:
- Derate power at higher temperatures (e.g. reduce 5–10% per 10°C above nominal)
- Altitude derating is typically required above 1000m due to reduced air density
- In sealed cabinets, ensure airflow is available or consider external heatsinking or forced ventilation
Example: A 5kW inverter installed in an IP54 outdoor enclosure at 45°C may require 20–25% power derating unless supplementary cooling is provided.
5. Output Voltage, Frequency and Load Compatibility
Check the required AC output voltage and frequency of your system:
- Standard outputs include 230Vac 50Hz (single-phase) or 400Vac 50Hz (three-phase)
- Some imported or legacy equipment may require 60Hz or specific output voltage tuning
Also consider:
- Whether a neutral is required (especially in three-phase systems)
- Sensitivity of the load to frequency variation (e.g. VFDs, timing circuits)
- Impact of voltage dips during dynamic load transitions
6. Waveform Quality and Harmonics
Industrial equipment—particularly modern electronics—requires pure sine wave output with low harmonic distortion.
- Avoid modified sine wave inverters in professional applications
- Look for <5% Total Harmonic Distortion (THD)
- Evaluate whether additional output filtering is required for long cable runs or sensitive electronics
Example: SCADA systems with PLCs or RTUs may experience fault conditions or communication issues if supplied with modified waveforms or excessive noise.
7. Mechanical Format, Mounting and Compliance
The inverter’s physical format and mechanical design should suit the installation environment and expected service conditions.
- Mounting options include wall mount, chassis mount, DIN rail, or 19” subrack. Select based on available space, enclosure layout and thermal management.
- Consider the required IP rating based on environmental exposure — e.g. IP20 for indoor panels, IP54/IP65 for outdoor or dusty environments.
- In vehicle-mounted or rail applications, verify that the inverter is rated for shock and vibration resistance to avoid premature failure or connector fatigue. Products used in rollingstock, heavy vehicles or mobile surveillance platforms may need compliance with relevant vibration standards (e.g. EN50155 or MIL-STD-810).
- Ensure proper orientation for airflow, cooling and service access. Some models must be mounted vertically to meet cooling performance requirements.
Compliance standards to review:
- EN50155 for railway rollingstock and signalling
- IEC 61000-6-2 / -6-4 for EMC immunity/emissions in industrial environments
- IEC 60335 / 61558 for safety in general appliance and control systems
Quick Reference Checklist
Category |
Consideration |
| Application | Is the inverter installed in a stationary, mobile, vehicle or rail environment? Does it require shock and vibration resistance? |
| Load | Inductive, Resistive or Capacitive type Load? Is high surge current required? |
| Duty Cycle | Continuous or intermittent operation? |
| Ambient | Max expected temperature and altitude? |
| Power Quality | Is pure sine wave output needed? THD limits? |
| Output Parameters | Voltage (230V/400V)? Frequency (50/60Hz)? |
| Form Factor | Wall Mount, Chassis Mount, 19” Mount, IP-Rating |
| Compliance | EMC, Rail, Utility or Telecom standards applicable? |
| Redundancy | Is N+1 redundancy or load sharing required for backup or fault-tolerant systems? |
| Monitoring | Are local or remote monitoring features needed (e.g. alarms, dry contacts, SNMP)? |
The Powerbox Inverter Platform
At Powerbox Australia, we don’t just sell inverters - we work closely with customers to identify and deliver the right inverter solution for their specific application.
Whether it’s a compact DC-AC inverter for an in-vehicle system, a rack-mounted unit for telecom infrastructure, or a configurable platform integrated into a hybrid DC power system, our team can support you from concept through to commissioning. Our offering includes both off-the-shelf products and engineered configurations, ensuring performance, compliance and long-term reliability.
We draw on a trusted portfolio of global inverter partners including Victron Energy, Premium PSU, CE+T Power, Delta_Eltek and Schaefer Elektronik. Each offers unique strengths — from railway-certified and convection-cooled models to scalable modular systems and flexible AC output configurations.
Powerbox adds value through:
• Application engineering and system-level support
• Pre-sale inverter selection based on load and environment
• Integration with batteries, DC-UPS, solar or fuel cell systems
• Local technical advice, configuration and lifecycle support
If you're designing an industrial, utility, telecom or vehicle-based power system, our team can help you make the right inverter selection, backed by over 40 years of experience in industrial power conversion.
Supplier Overview
Powerbox supports inverter platforms from:
• Powerbox Australia – Australian-built inverters engineered for on-board locomotive and heavy transport applications. Designed to operate from 74Vdc nominal input, delivering 230Vac output at 2kW to 4kW. These inverters feature high surge handling, rugged mechanical construction, and are purpose-built to withstand the mechanical and thermal stresses typical of rail environments. Ideal for integration into rollingstock systems where durability and local support are critical.
• CE+T Power – Modular, rack-mount inverters with inherent N+1 redundancy and hot-swappable architecture. CE+T’s solutions are optimised for telecommunications, data centres, and critical infrastructure applications where AC backup must be delivered from a DC power plant. Their compact form factor and integrated monitoring capabilities make them an ideal choice for high-availability systems where uptime and serviceability are essential.
• Eltek (Rectiverter) – An integrated inverter/rectifier platform purpose-built for industrial AC/DC UPS systems, combining rectification, inversion and AC transfer switching in a single module. Designed to operate within 48Vdc, 110Vdc, or 220Vdc power systems, the Rectiverter delivers flexible AC output with optional DC backup and native system integration. Commonly deployed in public safety networks, substation control systems, and critical telecom sites requiring compact, resilient power conversion.
• Premium PSU – Industrial-grade and EN50155-certified railway inverters designed for rollingstock and trackside applications. Available in convection-cooled or fanless variants, Premium PSU’s range supports 24Vdc to 110Vdc inputs and delivers clean, regulated 230Vac or 400Vac output. These inverters are engineered for rail vibration, extended temperature range, and compliance with rail EMC and surge immunity standards.
• Schaefer Elektronik – Rugged, high-spec industrial inverters offering configurable input and output voltages (e.g. 24Vdc to 220Vdc input, 230Vac or 400Vac output) and selectable output frequency (50/60Hz). Designed and manufactured in Germany, these units are suitable for use in power utilities, military platforms, and custom OEM applications where mechanical robustness, long lifecycle, and compliance with stringent environmental standards are required.
• Victron Energy – Pure sine wave, cost-effective inverters well suited to basic vehicle-mounted, mobile, and light industrial systems. These inverters are known for their ease of integration, flexible AC output options, and compatibility with both lithium and lead-acid battery systems. Ideal for use in utility vehicles, portable equipment enclosures, and remote infrastructure deployments where cost, reliability and simplicity are key.
Need Support?
For detailed product selection, application engineering or help with system integration, get in touch with the Powerbox team. We’re here to support your next inverter deployment - whether it’s a standalone unit or part of a complete power system.
