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 motorâ€™s crankshaft.

Simply,Torque is a special type of work that produces rotations.

Torque occurs when a Force acts on a radius

Torque = FÃ—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 = FÂ·v

P = VÂ·I

P = F.s ( For linear Motion )

P = Ï„Â·Ï‰ ( For Rotary Motion )

For Rotary motion, we are finding power so that it is easy for you to understand.

Power = (Force Ã— Distance ) / Time

Power = [Force Ã— Distance (Per Revolution) ] / Time ( in min. )

Distance per revolution = 2Ï€ Ã— Radius

Distance per revolution per time = 2 Ï€ Ã— Radius Ã— RPM

We know that Torque = Force Ã— Perpendicular Distance ( Radius )

Now, Force = Torque / Radius

As we know Power = [ Force Ã— Distance (Per Revolution ) ] / Time (in min. )

Now,putting the value of force and Distance

We get, Power = {Torque/Radius} Ã— { 2 Ï€ Ã— Radius Ã— RPM }

Finally, Power ( in Watt ) = Torque Ã— 2Ï€ Ã— RPM. Or,

Power (in watt ) = (Torque Ã— 2Ï€ Ã— RPS )/60

Now,we get

Torque = (Power Ã— 60)/(2Ï€ Ã—Rps)

Or, (Power )/(2Ï€ Ã—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 Â· meters) or kilogram. meters (Kg Â· m).

Gear Reducer Torque = 9550 * Motor power / Rated Power motorâ€™s input revolution*Ratio* gear reducer efficiency.

The above calculation is the torque equation.

Motor power = torque Ã· 9550 Ã— Rated powerâ€˜s motor input speed /Ratio /service factor.

Here useful converted relationship to Output torqueâ€™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:

**Ï„ = IÎ±**

where I is the rotational inertia (or moment of inertia), and Î± is the angular acceleration around an axis.

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