How to select a motor for your FPV
Motor size and performance parameters are different, and directly determine the power output of the aircraft, how to choose a suitable motor has become a major issue.
As we all know, the brushless motor model of the crossing machine is composed of two parts, one is the size of the stator, such as 2204 motor, the diameter of the stator is 22mm, and the height is 4mm; the other part is the kV value, which means that the speed of the motor increases with each 1 volt voltage increase, such as Each increase of 2V speed of 2300kV motor will increase 2300 rpm. Understanding this issue of motor thrust and efficiency will give you a better grasp. Everyone knows that P = UI, the larger P, the more power is consumed. Please note that the P value here is not 100% output as power, and may even be lower than 40% under extreme conditions. With reference to the full throttle push-to-weight ratio, the weight of the 210 and 220 series is calculated as 400g, and the 250 and 280 series is calculated as 600g. The following takes RC timer FR2304 2700kV motor as an example. The pull curve under different blades is as follows (take 3s battery as an example):
We found that all curves have a tendency to bend upwards, especially with the 5045 three-blade propeller (purple curve). At this time, the pulling force is only 250g, which means that the motor load is more likely to suddenly increase when the output is close to the limit. However, the increase in tensile force is small, in other words, the efficiency decreases, and the greater the degree of bending, the more serious the efficiency decline. This is not a good phenomenon. Imagine that you need a full-throttle rescue in case of an emergency, and the current does not increase much when the pull force is increased. As a result, the motor heats up and demagnetizes, the ESC heats up, and even burns. Therefore, while taking the tension into consideration, attention should be paid to the magnitude of the current and the slope of the curve. If one of these two items is too large, then this combination should be considered inappropriate. Based on this principle, let’s compare the popular 2205-2550kV and 2206-2100kV racing motors. Take the RC timer FR series as an example:
It can be easily seen that the working current range of the two motors is almost the same, and the difference between the maximum pull forces is less than 100g. It is obvious that the 2205 motor performs poorly under the 5045 three-blade propeller. If you like the feel of the three-blade propeller, do not choose It did, but it performed surprisingly well with the 6040 two-bladed paddle, and the efficiency did not drop but rise near the limit zone, so players who choose 280 racks with 6040 paddles must be surprised. Therefore, for different combinations, you need to analyze the curve specifically. Do not arbitrarily match or hearsay, and remember that the maximum pull is not necessarily the best. Here are the curves of the 2306 motor. Let’s compare them and find the one that suits you best:
In addition, talk about the ESC briefly. The choice of ESC is very narrow. The mainstream choices are generally 12A and 20A. Some violent configurations may use 30A. The rule is also very simple: general ESC can work at 150% overload for about 30 seconds without much damage. With reference to the motor curve, you can choose the appropriate one, such as full throttle 24A, you can also choose 20A ESC, because most people do not It will be full of throttle for a long time (of course, it is ordinary people …) If it exceeds 28A, it is recommended to get 30A. In short, it is safe and appropriate, and the scale can be controlled by itself.