In the world of radio-controlled vehicles, power and KV are two important parameters that every hobbyist needs to understand. Power, in this context, refers to the amount of energy that a motor can deliver and the higher the power, the better the performance of the vehicle. KV, on the other hand, refers to the constant that represents the RPM of the motor for every volt of voltage applied to it.
It is a common belief that a higher KV motor provides a higher power output, but is this true? In this article, we will dive into the relationship between KV and power and understand how to determine the power output of a brushless motor.
Table of Contents
Definitions
Before we get into the relationship between KV and power, let’s define these terms. Electrical power is defined as the voltage multiplied by current, and it is expressed in wattage. Mechanical power, on the other hand, is equal to RPM multiplied by torque. When we multiply RPM by torque in foot pounds, we need to divide it by 5252 to get the power in horsepower. If we use RPM in RADS per second and torque in Newton meters, we get the mechanical output power in wattage.
KV is equal to the RPM of the motor for every volt of voltage applied to it. It is a constant represented by the letter “K” and “V”, where “K” stands for constant and “V” refers to velocity. KV is equal to 1 divided by KT, where KT refers to torque.
Power Output Calculation
Now that we have defined KV and power, let’s look at how to calculate the power output of a brushless motor. We can use the KV value to calculate the RPM of a motor system. The formula is KV multiplied by the voltage. If the KV value is 2200 and the voltage is 22.2, we can calculate the RPM as follows: 2200 x 22.2 = 48,840.
Next, we calculate the torque. Torque is equal to KT multiplied by current. If we know the KV value, we can find the KT value by dividing 1 by KV. The formula for torque is KV multiplied by current.
Finally, we can calculate the power output by multiplying the voltage and current. Power = voltage x current.
Example
Let’s look at an example to understand this better. We will compare a 2500 KV motor with a 5000 KV motor, both of which are the same physical size. The 2500 KV motor has a maximum voltage of 24 volts and a maximum current of 50 amps, while the 5000 KV motor has a maximum voltage of 12 volts and a maximum current of 100 amps.
The maximum RPM of the 2500 KV motor is 60,000 RPM, and the maximum wattage is 1200 watts. The 5000 KV motor has a maximum RPM of 30,000 RPM and a maximum wattage of 1200 watts.
Conclusion
As we can see from the example, a higher KV motor does not necessarily provide a higher power output. The power output of a brushless motor is dependent on the voltage and current, not the KV value. The KV value is only used to calculate the RPM of the motor system, and it is the voltage and current that determine the power output.
In conclusion, a higher KV motor provides a higher RPM, but it does not guarantee a higher power output. To determine the power output of a brushless motor, we need to calculate the voltage and current.