The heat dissipation design of solar inverters directly affects their efficiency, lifespan, and stability, especially in high-power operation or high-temperature environments, where effective heat dissipation measures are crucial. The following are common cooling technologies and application scenarios:
1、 Passive heat dissipation (without active components)
Natural heat dissipation through structural design and material properties, suitable for small and medium power inverters (≤ 10kW) or low load scenarios.
1. Aluminum heat sink/fins
Principle: Utilizing the high thermal conductivity of aluminum alloy material (thermal conductivity coefficient of about 200W/m · K), accelerating air convection and heat dissipation by increasing the surface area (fin structure).
Design points:
The direction of the fins is perpendicular to the ground, utilizing the principle of rising hot air to enhance natural convection.
The spacing between fins is 8-15mm to avoid dust accumulation and heat dissipation caused by excessive spacing.
Example: 5kW single-phase inverters often use integrated die cast aluminum shells with fin thickness of 3-5mm and surface area of 0.5-1m2.
2. Heat pipe heat dissipation
Principle: The working fluid (such as water and ethanol) inside the heat pipe evaporates at the high temperature end, conducts heat to the low temperature end for condensation, and efficiently transfers heat through a phase change process (thermal conductivity is 100-1000 times that of aluminum).
Application scenario: IGBT module heat dissipation for medium power inverters (10-30kW), with one end of the heat pipe welded to the bottom of the module and the other end embedded with a heat sink.
Advantage: It can achieve long-distance heat conduction without a fan, avoiding the local hot spot problem of traditional heat sinks.
3. Phase change material (PCM) heat dissipation
Principle: Using phase change materials (such as paraffin and metal alloys) to absorb a large amount of latent heat during the melting process, delaying the rate of temperature rise.
Typical application: Used in conjunction with heat sinks, PCM is filled between the heat sink and power devices. When the temperature exceeds the phase transition point (such as 50 ℃), the material absorbs heat and melts, suppressing temperature fluctuations.
Limitations: It needs to be combined with other heat dissipation methods (such as air-cooled) to release stored heat, suitable for intermittent high load scenarios.
2、 Active heat dissipation (dependent on power components)
Forced heat exchange through active components such as fans and pumps, suitable for high-power inverters (≥ 20kW) or high-temperature environments.
1. Air cooling (forced convection by fan)
Classification and Design:
Axial flow fan: high air volume, low air pressure, suitable for overall cooling of large-area heat sinks (such as 30-100kW inverters), typical wind speed of 5-8m/s, noise ≤ 65dB.
Centrifugal fan: high air pressure, low air volume, used for directional heat dissipation in narrow spaces (such as centralized blowing of IGBT modules).
2. Liquid cooling heat dissipation (liquid circulation cooling)
Principle: The cooling liquid (deionized water or ethylene glycol solution) is driven by a pump to flow through heating components (such as IGBT modules and reactors), using the high specific heat capacity of the liquid (the specific heat capacity of water is 4.2kJ/kg ·℃) to remove heat, and then dissipated through an external heat exchanger.
System composition:
Cold plate: a metal plate (copper or aluminum) that is attached to power devices and has a flow channel design inside.
Circulating pump: head 5-10m, flow rate 5-15L/min, power consumption<100W.
Heat exchanger: air-cooled or water-cooled (such as used for power plant level inverters, paired with cooling towers).
3. Microchannel heat dissipation
Innovative technology: Micro scale flow channels (diameter 0.1~1mm) are machined at the bottom of power devices, and the cooling liquid directly contacts the heat source, quickly dissipating heat through extremely low thermal resistance (<0.5K/W).
3、 Composite heat dissipation technology (combining multiple methods)
Multiple heat dissipation methods are used to work together for complex environments or high power density requirements.
1. Air cooling+heat pipe combined heat dissipation
Typical configuration: The IGBT module is connected to the heat sink through a heat pipe, and the fan forcibly cools the heat sink, suitable for 20-50kW inverters.
Effect: The module junction temperature can be controlled below 80 ℃ (when the ambient temperature is 40 ℃), which is 10-15 ℃ lower than simple air cooling.
2. Liquid cooling+phase change material energy storage
Scenario: Inverters in high-temperature desert areas utilize liquid cooling for heat dissipation during the day and release stored heat through phase change materials at night to avoid condensation caused by temperature differences between day and night.
4、 Key parameters and testing of heat dissipation design
1. Thermal resistance (Rth) control
Definition: Thermal resistance=(device junction temperature - ambient temperature)/power consumption, unit: K/W.
Target value:
The thermal resistance from IGBT module to the casing is ≤ 0.5K/W.
The overall thermal resistance of the machine is ≤ 15K/W (i.e., at a power consumption of 1kW, the shell temperature is 15 ℃ higher than the environment).
2. Temperature rise test
Method: Run at rated load for 2 hours and use an infrared thermal imager to detect the temperature of key parts:
IGBT module junction temperature (Tj): ≤ 125 ℃ (limit temperature of silicon-based devices).
Surface temperature of electrolytic capacitor: ≤ 85 ℃ (life guarantee temperature).
Surface temperature of heat sink: ≤ 60 ℃ (safe temperature for human contact).
Summary: The core principle of efficient heat dissipation
Shortest thermal path: power device → thermal interface material (thermal conductive silicone grease, thermal resistance<0.5K/W) → heat dissipation substrate → cooling medium, reducing contact thermal resistance.
Airflow optimization: Maintain straight convection between the air inlet and outlet to avoid airflow short circuits (such as placing the air inlet at the bottom and the air outlet at the top).
Intelligent control: Combining temperature and load to dynamically adjust heat dissipation intensity, balancing energy efficiency and noise (such as when the fan stops at low loads, relying only on passive heat dissipation).
Through reasonable heat dissipation design, the inverter can maintain a conversion efficiency of ≥ 96% within a wide temperature range of -25 ℃~60 ℃, while extending the lifespan of core components to over 15 years. For extreme environments such as deserts and high humidity areas, targeted heat dissipation solutions need to be strengthened (such as increasing the density of dust-proof nets and using corrosion-resistant coatings), and overheating faults should be prevented through real-time thermal monitoring.
