Frequency conversion motor selection parameter method

Update:12 Jan 2019

1. Speed ​​requirement Speed ​​range In the basic param […]

1. Speed ​​requirement Speed ​​range In the basic parameters of the motor, the rated speed n0, the frequency range fmax and fmin are given. There are several options for the frequency range of the motor, and you need to find different products. When the speed range of the motor cannot meet the actual needs, a series-variable shifting group can be adopted to expand the shift range.

2. Power requirements Power characteristic curve The power characteristic curve of the motor determines the output power of the motor at various speeds. In any design, the output power of the motor is greater than or equal to the required power. Although the motor can work in the speed range, it should be noted that when the low-speed section of the constant torque zone is working, the power factor of the motor is very low and the efficiency is very low. When the speed is close to the minimum speed, the efficiency is only a few percent, and the motor generates a large heat. It consumes a lot of power and should not be used under frequent use conditions. It can only be used for occasional short-term use. When this requirement is not met, the speed reduction measures should be taken to enable the motor to achieve low speed output to the actuator at higher speeds. When the motor is connected in series with the step-variable speed, the speed is assigned to the high-speed transmission area and the low-speed transmission area. The speed distribution selects the transmission ratio, and the rated power of the motor should be minimized. It is necessary to consider the connection of the power curve to be reasonable.

3. Accuracy requirements The influence of the accuracy of the motor itself on the output accuracy is proportional to the ratio of the total gear ratio. When the motor accuracy cannot meet the requirements, the speed reduction drive can improve the accuracy. If it is not enough, the servo motor must be used.

4. Response speed requirements The response speed mainly affects the system acceleration performance. The response parameter of the motor is the parameter given by the motor output torque and its own moment of inertia. The system response should be calculated from the motor torque and the equivalent moment of inertia of the system to the motor shaft.

5. other requirements Mainly the starting characteristics and protective performance of the motor. Starting characteristics: When the system starts with load, the torque required is the highest during the process from static to acceleration to a certain speed. The reason is that the friction coefficient of the moving parts is static friction coefficient at rest, so the starting load is the largest, and the normal working load is needed. The torque is much reduced, and it is too wasteful to take a larger power motor. For this reason, it can be selected or customized according to requirements (in the starting area of ​​Figure 1, most of the motors are started with constant torque, but there are also motors with large starting torque, and the starting torque is several times larger than the torque.)