How to Dissipate Heat for Heavy-Load Frequency Inverters?

Introduction

A frequency inverter (Variable Frequency Drive, VFD) is an advanced power control device that uses frequency conversion technology and microelectronics to control AC motor power by adjusting the frequency of the power supply.

These devices consist of components such as rectifiers (AC to DC), filters, inverters (DC to AC), braking units, driving units, detection units, and microprocessor units. By using internal IGBT switching, an inverter VFD adjusts the output voltage and frequency, providing the motor with the required power for energy-saving and speed control purposes.

In addition to its core functionality, a variable frequency inverter includes several protective features, such as overcurrent, overvoltage, and overload protection. However, high loads and demanding environments require effective heat dissipation solutions to ensure the reliability and stability of these variable speed drives.

Safety Precautions for Heavy-Duty Inverters in High-Temperature Environments

To ensure the safe operation of heavy-load frequency inverters in challenging environments, follow these precautions:

Monitor Parameters

Regularly check and record the parameters displayed on the human-machine interface. Any abnormalities should be reported immediately.

Maintain Optimal Ambient Temperature

The operating environment should maintain a temperature range of -5°C to 40°C.If it’s over 40 degrees, you have to derate. For components like phase-shifting transformers, the temperature should not exceed 130°C.

Enhance Ventilation in High Temperatures

During summer or in high-temperature environments, enhance ventilation around the inverter. The air should be free from excessive dust, salt, acid, corrosive, or explosive gases.

Protect Against Rain and Moisture

Ensure that rainwater does not enter the inverter, especially during rainy seasons. Use sealed ventilation systems to prevent water ingress.

Clean Regularly

Clean the cabinet’s filter screens weekly. If the environment is particularly dusty, reduce the cleaning interval as needed.

Test Airflow with Paper

A standard A4 paper sheet should firmly adhere to the air inlet filter during normal operation, indicating proper airflow.

Maintain a Clean Environment

Keep the inverter room tidy, remove debris, and ensure proper ventilation and lighting. Cooling systems like air conditioners or fans must be in good working condition.

Failures in power electronics often arise from excessive heat, with over 50% of thermal failures caused by temperatures exceeding rated limits. Therefore, a well-designed heat dissipation strategy is crucial for ensuring reliability and high performance, especially for heavy-load variable frequency inverters that often operate at megawatt levels and generate significant heat.

How to Calculate Heat Dissipation?

Heat dissipation in a variable frequency drive depends on its internal components, such as isolation transformers, power units, reactors, and control systems. The following considerations are key:

Major Heat Sources

1. Power devices (e.g., IGBT, IGCT): Ensure PN junction temperatures do not exceed 125°C, and external casing temperatures remain below 85°C.
2. Power cabinets and units require optimized heat dissipation due to high thermal output.

Impact of Temperature Fluctuations

1. Studies show that when temperature fluctuations exceed ±20°C, the failure rate of components increases by up to 8 times.

Calculation Example

1. If a heavy-duty inverter operates at 1 MW with 3% losses, it generates 30 kW of heat.
2. Use this value to design the cooling capacity required for sustained operation.

Cooling System Design Points

Effective heat dissipation requires a combination of materials, system design, and cooling strategies:

High-Performance Components

Select components with high heat resistance and thermal stability to withstand elevated temperatures.

Low-Power Devices

Use low-loss IGBTs and other efficient devices to minimize internal heat generation. Optimize circuit design to reduce heating elements and adjust switching frequencies.

Cooling Methods

1. Forced Air Cooling: Employ fans to accelerate airflow and dissipate heat from components.
2. Liquid Cooling: Use liquid cooling for megawatt-level variable speed drives, as it efficiently transfers heat to external radiators.

Thermal Optimization

Lower ambient temperatures using air conditioners or industrial cooling systems to enhance heat dissipation.

By implementing these strategies, operators can ensure the frequency inverter operates reliably and efficiently, even in demanding conditions.