What is the relationship between motor torque and speed? First of all, we need to understａnd what is the motor output rated speed and motor output torque, which are closely related to each other.

Rated speed is the speed of the motor at rated power. That is, the motor speed when full load, so it is also called full load speed. It is represented by the symbol "N" and the unit is "revolution/minute".

Motor torque is the output torque of the motor, also known as motor torque, and the output power of the motor, the commonly used unit is N*m (N*m).

The torque output of the motor is related to the speed and power of the motor.

P=T*ω (power = torque * angular velocity)

T=9550P/n This formula is commonly used in engineering: torque; Power; The calculation formula of the relation between speed and speed.

T-- torque (unit: N.M) 9550 -- consider it as a constant P-- motor power (unit: kW)

N -- Output speed (unit: RPM)

The relationship between the speed and torque of the DC motor is expressed in a curve form, and the curve in FIG. is obtained.  

When the supply voltage is fixed, the characteristics of the DC motor become a straight line descending from left to right as shown in the curve.

The top left corner of the line is angular velocity without load, and the bottom right corner is torque at startup. In addition, when the supply voltage increases, the line will move parallel to the upper right, and when the voltage drops, it will move parallel to the lower left.

In the previous DC motor, you can see that torque increases in direct proportion to current. And this time we can know the nature of the speed will rise after increasing the voltage. This is a very useful property for control.

Another property that needs to be noted is that the DC motor, based on the relation T = KT, produces torque proportional to the current even when the speed is zero. This means that in the positioning control, even if a large external force is applied, it can control the current and keep the stop position.

The induction motor and stepper motor do not have it, this is only the dc motor and brushless DC motor have the property.