2.3. Motor Spec

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Quick Theory

Motor specification calculations compute thrust per motor and estimate ESC current requirements using the following formulas:

Thrust Per Motor Calculation

$T_{motor} = \frac{(T/W) \times m \times g}{n}$

ESC Current Calculation

$I_{ESC} = \frac{V_{avg} \times n}{P_{hover}}$

Symbol	Description	Unit
$T_{motor}$	Thrust Per Motor	N (Newtons)
$T/W$	Thrust-to-Weight Ratio	- (dimensionless)
$m$	Total Mass	kg (kilograms)
$g$	Gravitational Acceleration	m/s² (approx. 9.81)
$n$	Number of Motors	count
$I_{ESC}$	ESC Current	A (Amperes)
$V_{avg}$	Average Pack Voltage	V (Volts)
$P_{hover}$	Hover Power	W (Watts)

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The Motor Spec Calculator offers Standard and Advanced options for users to choose from.

Regardless of the option selected, the motor spec calculation results provide the following information:

• Thrust Per Motor [N]
• ESC Average Current [A]
• ESC Peak Current [A]
• Recommended ESC Rating [A]

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2.3.1. Standard

Input Parameters

• Drone Weight (kg)
• Target Thrust-to-Weight (T/W) Ratio
• Battery Voltage: Based on Li-Po battery
• Motor Count
• System Efficiency: Power efficiency

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2.3.2. Advanced

Input Parameters

• Drone Weight (kg)
• Target Thrust-to-Weight (T/W) Ratio
• Battery Cells: Based on Li-Po battery, 3.7V per cell
• Drone Type
• Motor Count (manual adjustment)
• System Efficiency: Power efficiency
• Rotor Diameter (inch)
• Air Density
• Figure of Merit (FM): Coefficient representing propeller performance efficiency

  To learn about propeller performance using CAD, please refer to Advanced Simulation: CFD Analysis.

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