Revealing the secrets of inverter safety

Although the photovoltaic inverter only accounts for 10% of the cost of the entire photovoltaic system, it is the core component of the entire system and directly affects the user's power generation income. There are many performance indicators to evaluate the quality of an inverter, such as efficiency, reliability, and grid interface friendliness. The author believes that no matter how the inverter manufacturer promotes it, the safety performance of the inverter must be put first. The picture below is a photo of a domestic household photovoltaic rooftop project inverter catching fire that was circulated on the Internet. The cause of the fire is unknown, but we can guess that unsafe products will definitely threaten the safety of users' lives and property. Therefore, when we choose an inverter brand, the first step we need to consider is the safety performance of the inverter.

So, what kind of inverter is a safe inverter? Although, as an electrical product, there is no 100% safe inverter, but excellent products must have considered potential risks at the beginning of the design and minimized the risks. This article will outline some possible safety risks of inverters for readers to make judgments when choosing inverters.

ELECTRIC SHOCK AND ENERGY HAZARD

Voltages other than safe voltages may cause electric shock hazards. The safe voltage limits are as follows:

The following points should be noted in the design of electric shock risk:

1. Inverters are basically protection category I devices, which are protected by basic insulation and chassis grounding. The grounding continuity of the contactable metal must be ensured, and a suitable connection method must be provided to ensure the reliable connection of the ground wire during on-site installation;

2. The selection of safe insulating materials should be determined according to the working voltage and working environment;

3. The electrical clearance and creepage distance must meet the requirements of the standard, and it should be considered that the clearance will not be reduced during transportation and installation;

4. Energy hazard means that the voltage is above 2V and the energy available after 60 seconds is 240VA, or the voltage is above 2V and the stored energy is greater than 20J;

5. Energy hazards should pay attention to the following points in design:

There should be no energy hazards in areas accessible to operators, such as the ports of the inverter connector;

If energy hazards are unavoidable in areas accessible to maintenance personnel, there should be corresponding warning signs and safe operating procedures should be explained in the manual.

Fire and heat hazards

Fire hazard refers to the spontaneous combustion of a product and its spread to the surrounding environment, causing huge personal injury and property damage. For example, the spontaneous combustion of mobile phones is well known.

Two ways to reduce the risk of fire:

Use fire resistant enclosures and select and use materials that reduce the risk of natural or ignition hazards;

Without using a fireproof enclosure, single fault tests are performed on all components to verify that there is no spontaneous combustion or ignition. Thermal hazards refer to burns caused by operator contact with hot accessible parts; the insulation level of insulation is reduced or the performance of safety components is reduced due to the influence of heat; and flammable gases or liquids are generated due to the influence of heat.

The following points should be considered in the design of thermal hazards:

Reasonable layout and good design should be adopted to keep the heating components within a reasonable and safe temperature range;

Consider the degradation of components under long-term thermal conditions;

Limit the temperature of accessible surfaces;

Limit the temperature of the installation surface. The installation surface is not allowed to exceed 90℃.

Mechanical hazards

Mechanical hazards include personal injury caused by sharp edges or corners, moving parts, projectiles, etc. of the product, as well as personal injury and property damage caused by the stability of product installation.

Mechanical hazards should pay attention to the following points in design:

Moving parts should be sealed or equipped with protective parts to prevent human contact, such as fans;

The stability of the floor-mounted high-power inverter should be considered when tilted 10 degrees in any direction in the normal installation position, and the door or other removable device should be in the most unfavorable position at this time;

For wall-mounted small and medium-power inverters, the bracket structure should be able to withstand a force four times the weight of the product without deformation or damage.

Noise Hazards

Any sound that is annoying or unnecessary can be called noise. If the noise measured 1 meter away from the inverter is greater than 80 decibels, it is considered to be a noise hazard.

For small and medium power, although there is no noise hazard, since the use environment is a residential area, the noise risk should be reduced as much as possible to avoid any noise that affects people's lives.

For high-power inverters, if there is a noise risk, the risk should be identified and guidance should be given to reduce the noise.

Chemical hazards

Chemical hazards refer to the materials used in the inverter containing hazardous chemicals, or the production of toxic chemicals or vapors during operation. When choosing an inverter, you should consult the manufacturer or dealer to find out the hazardous substances and content of the product. Products that do not meet national safety standards should not be selected.

Radiation hazards

Radiation hazards include nuclear radiation, ionizing radiation, and electromagnetic radiation. The radiation hazard in the inverter is mainly electromagnetic radiation. Electromagnetic radiation should be designed to ensure that the radiation of the inverter meets the requirements of electromagnetic compatibility standards and does not cause any impact on other devices of the user. It is particularly important to note that the inverter should be tested and verified under various harsh conditions.