Motor Torque calculations
Motor Torque calculations is very easy for anyone if you know the basic idea and formula related to it.
The 3 factors that determine the type of work A motor can produce
1.speed
2.Torque
3.Horsepower
But here we will know about how to calculate Torque for motors.
Work:- Work is defined as Force applied over a distance but, In the case of Flywheel wenches and motors , The work is called Torque.
Torque :- Torque is a measure of how much a force acting on an object causes that object to rotate.
Or,
Torque is a rotating force produced or available at a motor’s crankshaft.
Simply,Torque is a special type of work that produces rotations.
Torque occurs when a Force acts on a radius
Torque = F×r , typical unit for measurements of Torque is N-m or pound feet.
Why ,I am saying Torque is a type of work.When you will see the unit of both you will understand.
So,to calculate Torque we need two things
1.Force Applied
2.Distance of force from centre of rotation.
Power :- Rate of doing work. Unit of power is watts (J/s) or horse power.
P = E/t
P = F·v
P = V·I
P = F.s ( For linear Motion )
P = τ·ω ( For Rotary Motion )
For Rotary motion, we are finding power so that it is easy for you to understand.
Power = (Force × Distance ) / Time
Power = [Force × Distance (Per Revolution) ] / Time ( in min. )
Distance per revolution = 2π × Radius
Distance per revolution per time = 2 π × Radius × RPM
We know that Torque = Force × Perpendicular Distance ( Radius )
Now, Force = Torque / Radius
As we know Power = [ Force × Distance (Per Revolution ) ] / Time (in min. )
Now,putting the value of force and Distance
We get, Power = {Torque/Radius} × { 2 π × Radius × RPM }
Finally, Power ( in Watt ) = Torque × 2π × RPM. Or,
Power (in watt ) = (Torque × 2π × RPS )/60
Now,we get
Torque = (Power × 60)/(2π ×Rps)
Or, (Power )/(2π ×Rpm)
Must read :- Calculating brake horsepower
This is the basic formula for calculations of Torque but only problem you face is unit conversion.
Note :-For calculations of Torque if motor you need to know power ( in watt or horsepower)
Now, I am writting directly formula with unit.
Torque in Imperial units can be calculated as
Tinlb = Php 63025 / n
where
Tinlb = torque (in lbf)
Php = horsepower delivered by the electric motor (hp)
n = revolution per minute (rpm)
Alternatively
Tftlb = Php 5252 / n
where
Tftlb = torque (lbf ft)
1 ft lbf = 1.356 Nm
Torque in SI units can be calculated as
TNm = PW 9.549 / n
where
TNm = torque (Nm)
PW = power (watts)
n = revolution per minute (rpm)
DC Motor Torque Calculations
the total torque developed of a DC machine is,
This torque equation of DC motor can be further simplified as:
Gear motor Torque calculations
Gear box output :- Multiply the gear ratio by the input torque
The torque unit is N.m (Newton · meters) or kilogram. meters (Kg · m).
Gear Reducer Torque = 9550 * Motor power / Rated Power motor’s input revolution*Ratio* gear reducer efficiency.
The above calculation is the torque equation.
Motor power = torque ÷ 9550 × Rated power‘s motor input speed /Ratio /service factor.
Here useful converted relationship to Output torque’s unit :
100 N.m = 885.07457 9349 Ibs in
100N.m = 885.07458 ibf.in
100 N/m = 0.5710147 ib/in
Servo motor Torque calculations
Torque Required By a Servo Motor = (Torque Due to Force of Gravity on Links and Payload) + (Torque Due to Angular Acceleration of Links and Payload)
This torque due to angular acceleration is calculated using the following equation:
τ = Iα
where I is the rotational inertia (or moment of inertia), and α is the angular acceleration around an axis.
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