- KNOW THE LOAD CHARACTERISTICS
Line-operated motors fall into three general categories: constant torque, which changes abruptly, and torque, which changes gradually over time. Bulk material conveyors, extruders, positive displacement pumps, and compressors run at relatively steady torque levels without air unloaders.
The torque (or horsepower) should be known to size a motor for these applications. In choosing the best engine, consider the highest continuous load point, typically at the highest speed. Load demands by elevators, compactors, punch presses, saws, and batch conveyors change abruptly from low to high quickly, often in a fraction of a second. In contrast, loads from centrifugal pumps, fans, blowers, compressors with unloaders, and similar equipment vary over time.
- GET TO KNOW THE HORSEPOWER
Selecting the horsepower of the motor is the next task. There is only one rule of thumb to choose an engine with the right horsepower: to choose only what you need and avoid the temptation to oversize or undersize.
Another thing to consider while buying a motor is its inertia. Consider the inertia, particularly during the startup of the engine. Every load represents some value of inactivity, but punch presses, ball mills, crushers, and gearboxes drive large rolls, and certain types of pumps require high starting torques due to the huge mass of the rotating elements. Motors are rated as one of their various design types for their ability to endure the heat of that starting and pull-up.
- ADJUST FOR DUTY CYCLE
A motor must handle the load when it starts, runs, and stops. This is called the duty cycle. There are different kinds of duty, as given below–
Continuous duty: Continuous duty is considered the simplest and most efficient application. The constant duty cycle begins with a startup, followed by long periods of steady operation where the motor’s heat can stabilize as it runs.
In a motor with continuous duty, the temperature has a chance to stabilize. After that, it can be operated safely at or near its rated capacity because the temperature has a chance to stabilize.
Intermittent Duty: Intermittent duty is more complicated than continuous duty, as the number of their landings measures commercial airplanes’ life. It is the same way a motor’s life is proportional to the number of stars it makes. Frequent starts in an engine can shorten its life because the inrush current at startup heats the conductor rapidly, challenging it. This results in the production of a lot of heat. Because of this heat, the can only have a limited number of starts and stops that they can make in an hour. This can cause an obvious problem that can be hard to deal with.