A helpful netizen shared a case: A 37kW motor, using a star-delta reduced-voltage starter to drive a water pump, failed to start when the water supply was fully open, and the pump could not operate. Later, the water supply was turned off, and as the motor started, the water supply was gradually opened until the motor and pump were running normally. This case illustrates the importance of matching the motor’s starting performance with the load.
The starting process of an electric motor is inherently a process of balancing driving torque and resisting torque. On the one hand, we can improve the starting performance of the motor by modifying its parameters, such as controlling the starting current to increase the starting torque; on the other hand, we can achieve the starting purpose by adjusting the load.
When the equipment connected to the motor can start under light load or even no load, the starting problem of the motor can be solved by adjusting the load size.
Based on the design principles of motors, the starting torque should be greater than the rated torque, which is specifically stipulated in the technical specifications of motors, and is generally around twice the rated torque. The starting torque is the electromagnetic torque at the moment the motor starts, and its magnitude is equal to the static friction torque of the motor load, which is also the moment when the motor starting current is the largest.
Analyzing the operating state of the motor rotor, the starting process is the process of the motor rotor changing from static to dynamic and then to rated speed. From the perspective of the change in inertia of an object, the greater the load driven by the motor, the more difficult it will be to start. Conversely, if the load driven by the motor is appropriately reduced, the motor will be easier to start.
However, for motors that start directly under constant load, the only effective measures to improve the motor’s performance are to optimize and improve the motor itself. These measures include taking measures to improve the slot shape of the squirrel-cage rotor, adding resistance to wound rotor motors, and using variable frequency starting, which is currently widely used. These are all effective measures to help and improve motor starting.
We can also see from the comments of enthusiastic netizens that, for working conditions with adjustable loads, the load can be gradually adjusted according to the actual starting situation of the motor, and the load will basically reach the rated load state after the motor starts.
Post time: Dec-14-2025