The relationship between torque and power of DC motors
The power of the DC motor should be selected according to the power required by the production machinery, and the motor should be operated under extra load as much as possible. Pay attention to the following two points when selecting:
① If the motor power is too small. The appearance of a "small horse cart" will form a long-term overload of the motor. Make its insulation damaged by heat. Even the motor was burned.
② If the motor power is too large. The appearance of "Big Marathon Trolley" will appear. The output mechanical power cannot be fully utilized, and the power factor and power are not high, which is not only obscure to users and the power grid. And also waste of electricity.
To accurately select the power of the motor, it is necessary to pass the following calculations or comparisons:
P = F * V / 1000 (P = Calculated power KW, F = Needed pulling force N, working machine linear speed M / S)
For the stable load continuous operation method, the power of the required motor can be calculated by the following formula:
P1 (kw): P = P / n1n2
Where n1 is the power of the production machinery; n2 is the power of the motor, that is, the power of the transmission.
The power P1 obtained by the above formula is not necessarily the same as the commercial power. thus. The extra power of the selected motor should be equal to or slightly greater than the calculated power.
In addition. The most common method is to select the power of the motor by analogy. The so-called analogy. It is compared with the power of the motor used in similar production machinery.
The specific method is: understand how much power is used by similar production machinery of this unit or other nearby units, and then select a nearby power motor for test run. The purpose of the test run is to verify that the selected motor matches the production machine.
The verification method is: make the motor unit move to produce mechanical operation, measure the working current of the motor with a clamp ammeter, and compare the measured current with the extra current marked on the motor nameplate. If the actual working current of the electric power machine is not significantly different from the extra current marked on the spleen. Then indicate the power of the selected motor
suitable. If the actual operating current of the motor is 70% lower than the extra current marked on the nameplate. It indicates that the power of the motor is too large, and the motor with a smaller power should be interchanged. If the measured motor operating current is more than 40% greater than the extra current marked on the nameplate. It indicates that the power of the motor is too small, and the motor with a larger power should be interchanged.
In practice, you should think about torque (torque). Motor power and torque have accounting formulas.
That is T = 9550P / n
In the formula:
n—extra speed of motor, r / min;
The output torque of the motor must be greater than the torque required by the work machine, usually a safety factor is required.
The derivation of the relationship between power, torque and speed is as follows:
Power = force * speed
P = F * V --- Equation 1
Torque (T) = Torque (F) * Effect Radius (R) ------ Introduce F = T / R --- Formula 2
Linear speed (V) = 2πR * speed per second (n seconds) = 2πR * speed per minute (n minutes) / 60 = πR * n minutes / 30 --- Formula 3
Substituting formulas 2 and 3 into formula 1 gives:
P = F * V = T / R * πR * n minutes / 30 = π / 30 * T * n minutes ----- P = power unit W, T = torque unit Nm, n minutes = speed unit per minute RPM
If the unit of P is changed to KW, then it is the following formula:
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 9550 coefficient between power and torque * speed. . .
It is suitable for the connection and mutual conduction between the additional power, additional speed and additional torque of the servo motor, but the actual additional torque value should be measured in practice. Due to the question of energy conversion power, the fundamental value is generally the same and will be slim Decrease.