It is not uncommon for many clients, who intend to procure solar PV systems, to emphasize on the cost or kVA capacity of a solar inverter. Depending on the client, some may argue that the cost of a particular brand of solar inverter is too expensive compared to other brands of the same kVA rating. However, there are several other parameters for determining the quality, cost and suitability of a solar inverter in a given application. What this implies is that a client needs to understand what type of use the solar system will be put to. Then discuss it with a solar PV expert who is knowledgeable to match the client's need with the appropriate solar inverter specification. This article will discuss two of those inverter specifications. They include low-frequency inverters and high-frequency inverters.
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Introduction to High-Frequency and Low-Frequency Solar Inverters
High-frequency inverters and low-frequency inverters are two different types of inverters used to convert direct current (DC) power into alternating current (AC) power. Each of these inverters has different characteristics from the other and each of them is more suitable in a given application than the other. Below are the features of the two types of inverters.
Features of High-Frequency Solar Inverters
1 Power Factor: The power factor is 1, indicating that high-frequency inverters have no reactive power during energy conversion, making them highly efficient.
2 Self-Consumption: The self-consumption power is less than 0.1 watts, indicating very low power consumption during operation.
3 Load Capacity: High-frequency inverters cannot handle full loads of inductive loads and have poorer overload capacity. The appropriate power capacity of the high-frequency inverter should be about 2.5 to 3 times the actual load power, considering the starting current of inductive loads is generally 4 to 7 times the rated current. For example, if you choose a 10kVA high-frequency inverter, it can handle a maximum load of 3.5kW to 4.0kW.
Features of Low-Frequency Solar Inverters
1 Power Factor: The power factor is 0.8, indicating the presence of some reactive power when converting electrical energy. This is why many low-frequency inverters are marked as kVA. For example, a 1000kVA low-frequency inverter with power factor 0.8 will produce a maximum output of only 800W.
2 Self-Consumption: The self-loss is very large. That is, the self-consumption ranges from 200 to 300 watts, meaning the inverter consumes a certain amount of power during operation.
3 Strong Load Capacity: It operates stably and reliably with strong overload capacity and resistance to shocks, making it particularly suitable for situations where the load is primarily inductive. It helps to increase power load which translates to increase productivity.
Differences Between High-Frequency and Low-Frequency Inverters
|S/N||High-Frequency Inverters||Low-Frequency Inverters|
|1||They have no reactive power during energy conversion.||There is presence of some reactive power when converting electrical energy.|
|2||They are highly efficient.||They are less efficient.|
|3||They support operation without batteries.||They must be used with batteries.|
|4||They are smaller and lighter compared to low-frequency inverters, providing more convenience in terms of portability.||They are generally heavier compared to high-frequency inverters within the same power range.|
|5||High-frequency inverters support parallel operation, allowing multiple inverters to be connected simultaneously, with a maximum of up to 9 units.||Currently, low-frequency inverters do not support parallel operation.|
Similarities Between High-Frequency and Low-Frequency Inverters
They both produce pure sine wave as an output waveform. A sine wave is what you get from your local utility company and (usually) from some generators.
Conclusion and Assessment Questions
The choice of inverter should be based on actual needs and application scenarios. Low-frequency inverters are suitable for environments requiring high stability and resistance to interference, and where the load is primarily inductive. High-frequency inverters are suitable for environments that require smaller size, lighter weight, lower cost, and support for parallel operation.
As an installer, how would you identify an low-frequency inverter and a high-frequency inverter in a vendor’s shop? Just join our training programming to equip yourself with the trick and skills.
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