1. What is the Motor kV to RPM Calculation?

The kV to RPM calculation estimates the rotational speed of an electric motor based on its kV rating (RPM per volt) and the applied voltage, accounting for mechanical and electrical losses.

2. How Does the Calculator Work?

The calculator uses the following equation:

Where:

• \( kV \) — Motor velocity constant (RPM per volt)
• \( V \) — Applied voltage (volts)
• \( Losses \) — Mechanical and electrical losses (RPM)

Explanation: The kV rating indicates how many RPM the motor will turn per volt with no load. Actual RPM under load will be lower due to various losses.

3. Importance of RPM Calculation

Details: Knowing the expected RPM helps in motor selection, propeller matching, and performance prediction for RC vehicles, drones, and other electric motor applications.

4. Using the Calculator

Tips: Enter the motor's kV rating (found in specifications), the voltage you'll be using, and estimated losses (if known). For no-load testing, losses can be set to zero.

5. Frequently Asked Questions (FAQ)

Q1: What exactly is motor kV?
A: kV is the motor's velocity constant, representing RPM per volt with no load. A 1000kV motor will spin at approximately 1000 RPM for each volt applied under no-load conditions.

Q2: How do I estimate losses?
A: Losses typically range from 5-20% of the theoretical RPM. For precise measurements, compare calculated RPM with actual tachometer readings.

Q3: Does battery voltage affect the calculation?
A: Yes, use the actual voltage under load (which may be lower than nominal battery voltage due to voltage sag).

Q4: Why does my motor spin slower than calculated?
A: Load, inefficiencies, voltage drop, temperature, and motor quality all contribute to lower actual RPM than theoretical.

Q5: Can I use this for brushless and brushed motors?
A: Primarily for brushless motors. Brushed motors have different characteristics and may require different calculations.