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Detailed explanation of the relationship between torque, speed and power

Date:2024-05-10   Author:XINDA MOTOR
For commonly used motors, the three indicators of torque, speed and power are related.

Torque, speed and power are the three main parameters describing power systems in mechanical engineering. The relationship between them can be expressed by the following formula:
1. Power = Torque × Speed
2. Torque = 9550 × power/speed
3. Speed = power / (2π × torque)
Simply put, under the premise of a certain power, the speed and torque are inversely proportional. That is, when the speed increases, the torque will decrease; conversely, when the speed decreases, the torque will increase. This is because torque represents the amount of twisting force an object produces, while rotational speed represents the number of times an object rotates per minute. When the power is kept constant, there is this mutual restriction relationship between these two parameters.
In addition, the output torque of the motor must be greater than the torque required by the working machine to ensure that the motor can effectively drive the working machine.
The specific conversion relationship between them is as follows:
Power = Torque X Speed/9550
(Power P: kW, torque T: Nm, speed n: rpm)
P=Tn/9550
For example, the parameter table of Panasonic servo motor:

Corresponding motor power: 0.64X3000/9550=0.20 Kw
----Dividing line----
Why is there a coefficient of 9550 between power and torque*speed?
The derivation of the relationship between power, torque and speed is as follows:
① Power = force * speed
P=F*V------------------------------------------------ ---------------------[Formula 1]
② Torque (T) = Torque (F) * Radius of action (R) ------ Push out
F=T/R------------------------------------------------ --------------------------[Formula 2]
③Linear speed (V)=2πR*rotation speed per second (n seconds)=2πR*rotation speed per minute (n minutes)/60=πR*n minutes/30--------------- ----------------[Formula 3]
Substituting formulas 2 and 3 into formula 1 we get:
P=F*V=T/R*πR*n points/30=π/30*T*n points-----
P=power unit W,
T=Torque unit N·m,
n minutes = rpm unit rpm
If the unit of P is changed to KW, then the formula is as follows:
P*1000=π/30*T*n
30000/π*P=T*n
30000/3.1415926*P=T*n
9549.297*P=T*n
This is why there is a coefficient of 9550 between power and torque*speed.