This section provides overview, applications, and principles of electronic loads. Also, please take a look at the list of 11 electronic load manufacturers and their company rankings.
An electronic load is a loading device that can provide a pseudo-resistance to a circuit. Conventionally, a load has been provided by incorporating a resistor.
However, this requires a huge resistor to apply a large load. Furthermore, to freely change the resistance value, another resistor with a different resistance must be reassembled.
The advantage of electronic load is that the resistance can be changed arbitrarily. It is also possible to perform abrupt switching that cannot be done by hand. For this reason, electronic load is also called resistive load devices.
Electronic loads are used to test the performance of batteries and power supplies. In addition to load performance tests of power supplies and charge/discharge tests of batteries, they are recently used to evaluate stack performance when fuel cells installed in fuel vehicles are connected in series.
Unlike the use of variable resistors to control load current, there is no need to manually move the sliding parts. Because computer-based control is possible, testing can be performed automatically while freely controlling the load current.
Setting an arbitrary resistance value using electronic loads are accomplished by using semiconductor elements instead of resistors as in the past. These semiconductor elements generate a pseudo-resistance by consuming or converting the input power as another form of energy.
There are two types of power consumption/conversion methods.
Thermal Conversion Type Electronic Loads
The input power is converted into heat by semiconductor devices. This produces a voltage drop, which has the same effect as passing through a resistor. However, because of the heat generated, a heat removal system is required.
Power Regenerative Electronic Loads
The input power is converted into alternating current by an inverter. The converted current is returned to the power distribution network, so power consumption is small and there is no need to worry about exhaust heat.
However, since regenerated power energy is returned to the power grid, it is necessary to check in advance whether the environment is suitable for grid-connected operation.
In electronic loads devices, CC, CR, etc. indicate the operating mode of the electronic loads. The following four modes of operation are available for electronic loads. When actually testing, use the correct mode with the correct setting value, and test the device under test to avoid overloading the device under test.
Constant Current (CC) Mode
Operates to deliver a set current regardless of input voltage, within the capability of the SUT (e.g., power supply) and electronic loads. The electronic loads adjusts the current flow so that it does not change even if the voltage of the device under test fluctuates. Therefore, in constant current (CC) mode, the load current is constant with respect to the input voltage.
Constant Resistance (CR) Mode
Within the capabilities of the device under test (e.g., power supply) and the electronic loads, the electronic loads maintains a constant set resistance value, like a fixed resistance. Passive loads are characterized by the fact that after a period of instability immediately after power-on, the balance between heat generation, resistance value, etc. is balanced and a certain resistance value is exhibited.
In constant resistance (CR) mode, the load current fluctuates proportionally to the input voltage, and is used for battery and battery capacity tests, start-up tests of electronic equipment, etc.
Constant Voltage (CV) Mode
Within the capability of the device under test (e.g., power supply) and the electronic loads, the electronic loads works to maintain a set voltage. When the voltage drops, the resistance of the load is increased and the load is controlled in a direction to suppress the current.
In the low voltage (CV) mode, the load current fluctuates and the input voltage remains constant. Because the voltage is constant, the device is used for testing fuel cells, battery chargers, and other devices.
In battery charger testing, complex battery voltage behavior can be simulated with electronic loads.
Constant Power (CP) Mode
Within the capabilities of the device under test (e.g., power supply) and the electronic loads, the electronic loads works to draw power at a set power setting. First, the voltage of the device under test is measured, then the appropriate current is determined from the voltage and the set power value, and the current is drawn so that it flows.
Electronic loads are an indispensable device in the development of power sources, such as power supplies and batteries, for testing them. Although it is possible to provide power with resistors, it is difficult to vary the load intentionally, and the heat generated makes it difficult to maintain stability, among many other inconveniences.
In such cases, programmable electronic loads can be used to create the load in the state required for the test. Since the state of the load is easy to control, it is possible to inspect the load from various angles. When selecting electronic loads device, the following points should be considered
The capacity of the electronic loads device, but it is often not necessary up to the capacity of the power supply of the device under test. For example, when testing a 12V 50A power supply, it may seem that electronic loads of 600W or more is required because the capacity of the power supply is 600W, but in reality, it is often not intended to flow 50A at 12V.
For example, if 20A at 12V and 50A at 5V, then electronic loads of 240W or more would be sufficient.
Electronic loads are generally difficult to use at very small voltages. The minimum voltage that electronic loads device can handle is called the minimum operating voltage.
As can be seen in the maximum load curve of electronic loads device, the lower the voltage, the smaller the voltage, the smaller the current that can be drawn. In other words, when the voltage is low, there is a range in which the device is practically unusable.
Therefore, it should be noted that the equipment under test may not operate if the voltage is below this minimum operating voltage. When selecting electronic loads, it is important to check the minimum voltage at the time of measurement and the minimum voltage that the electronic loads device can handle.
Some electronic loads have products that have a low ambient temperature at which the maximum load can be swept. Particular attention should be paid to resistive-consumption electronic loads, because the ambient temperature rises due to heat generation.
There may be a limit to the time that the maximum load can be maintained. Depending on the method of use, it may be necessary to check the catalog or spec sheet in advance.
*Including some distributors, etc.
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