introduction:
What is a fuel cell?
The basic working principle of all fuel cells is the same: the chemical energy of hydrogen is converted into electrical energy. But several different types of fuel cell technology have been developed. In addition to PEM, PAFC and SOFC, there are alkaline fuel cell (AFC) and molten carbonate (MC) fuel cells. Among them, PEM fuel cells are widely used in the automotive industry due to their relatively low operating temperatures and high efficiency.
However, a single cell can only produce a voltage of no more than 1V, so for testing low-voltage energy sources such as fuel cells, there is a problem in how the test device can carry a large current under a low voltage state.
Idex test program introduction:
Hardware requirements:
Today's electronic loads have internal resistance, so the corresponding minimum load voltage is higher when the current is large. So how can we achieve low voltage load or even OV load?
At this time, we need an "auxiliary power supply", which is used to provide the voltage of the internal transistor of the load in the linear region, that is, the minimum operating voltage, when the electronic load is loaded with different currents.
Take the Idtech IT8811 electronic load as an example, as shown in Figure 1:
figure 1
It is apparent from the figure that the larger the load current, the higher the minimum operating voltage of the load.
To achieve the OV load of the electronic load, the "auxiliary power supply" can be a very common source of regulation, but the current on the parameter must be higher than the maximum current value to be carried by the electronic load.
Program architecture:
Understand the specific requirements of the "auxiliary power supply", let's take a look at the wiring method and various points of attention for implementing this test solution, as shown in Figure 2:
figure 2
It is not difficult to see the wiring method of this test scheme from Figure 2, but the necessary point is that the remote sense function of the electronic load must be turned on and the positive and negative sense lines are connected to the positive and negative electrodes of the fuel cell. The purpose of this connection is to let the voltage sampled by the electronic load sense terminal be the voltage across the fuel cell, so that the voltage displayed on the electronic load panel is the voltage across the real fuel cell, so the auxiliary voltage of the "auxiliary power supply" can be ignored. .
Precautions:
1. Since the current noise of the “auxiliary power supply†itself is superimposed on the test product, we need to choose a low-noise “auxiliary power supply†as much as possible.
2. The electronic load must be selected to have a rated power greater than the sum of the power of the test product and the power of the "auxiliary power supply". For example, if the power of the test product is 100W, it is not enough to select the rated power of the electronic load to be 100W. Assuming that the power of the “auxiliary power supply†is 50W, we need to select 150W or more for the rated power of the electronic load.
In summary, the difficulty in the test of fuel cells and low-voltage products is the load test at 0V or ultra-low voltage. The test solution provided by Idex is simple, convenient and low-cost, without special hardware support. Realize OV loading. The electronic loads mentioned in the test scheme as well as the "auxiliary power supply" Itech are available.
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