Constant Torque Drives vs Variable Torque Drives04/06/2017The vast majority of drives in industry are of the constant torque variety. The work that they do requires a steady unchanging level of power to accomplish their tasks. Some of these include general machinery such as cranes and hoists, conveyors, presses, mixers, extruders, crushers, and more. The horsepower required for these applications doesn’t change throughout their operation even if the speed does change. Variable torque applications are ones in which the horsepower requirement does change during the operation. Two of these types are fan applications and pump applications. The reason for this is because they require a base level of current or breakaway torque during startup and acceleration, but once they achieve their full operation speed, less horsepower is necessary to maintain the inertia. As the motor begins to accelerate, the torque drops off and will reach a minimum value that will be approximately 25 percent to 40 percent of the value of that of synchronous speed or the speed at which the motor would theoretically operate if the load was zero, there was no load due to bearing friction and the rotor had no electrical losses. An AC motor’s synchronous speed is determined by the operating frequency and the number of poles in the stator winding. Using variable torque drives for fan and pump applications is more cost effective than constant torque drives over the life of the drive because the motor requires less power to maintain once the nominal operational speed is reached. Less power used means less money spent on the particular application. Very often you will see drive capacity rated in horsepower. In reality this is only a close approximation and should only be used as a general guideline of a drive that is needed. Horsepower ratings differ from manufacturer to manufacturer so much that the rating may almost seem arbitrary instead of arrived at by a formula. When it comes to making the determination of what size of drive that you have or what size of drive you will need, the more appropriate specification to use is the current rating. More specifically you want to know what is the full load amperage of the motor that the drive will be running? Then you want to go by the output amp rating of the drive as it will be different from the input amp rating. The output amps is what to match to the FLA rating of the motor. The drive should be sized at the same FLA rating or higher. A drive with a lower amp rating may drive your motor, but would not drive it at its full operating capacity. If you have a drive in need of repair, whether it’s a constant torque or variable torque, call 800-732-4695 to reach the drive experts at Precision Electronic Services. Back To Blog
Constant Torque Drives vs Variable Torque Drives04/06/2017The vast majority of drives in industry are of the constant torque variety. The work that they do requires a steady unchanging level of power to accomplish their tasks. Some of these include general machinery such as cranes and hoists, conveyors, presses, mixers, extruders, crushers, and more. The horsepower required for these applications doesn’t change throughout their operation even if the speed does change. Variable torque applications are ones in which the horsepower requirement does change during the operation. Two of these types are fan applications and pump applications. The reason for this is because they require a base level of current or breakaway torque during startup and acceleration, but once they achieve their full operation speed, less horsepower is necessary to maintain the inertia. As the motor begins to accelerate, the torque drops off and will reach a minimum value that will be approximately 25 percent to 40 percent of the value of that of synchronous speed or the speed at which the motor would theoretically operate if the load was zero, there was no load due to bearing friction and the rotor had no electrical losses. An AC motor’s synchronous speed is determined by the operating frequency and the number of poles in the stator winding. Using variable torque drives for fan and pump applications is more cost effective than constant torque drives over the life of the drive because the motor requires less power to maintain once the nominal operational speed is reached. Less power used means less money spent on the particular application. Very often you will see drive capacity rated in horsepower. In reality this is only a close approximation and should only be used as a general guideline of a drive that is needed. Horsepower ratings differ from manufacturer to manufacturer so much that the rating may almost seem arbitrary instead of arrived at by a formula. When it comes to making the determination of what size of drive that you have or what size of drive you will need, the more appropriate specification to use is the current rating. More specifically you want to know what is the full load amperage of the motor that the drive will be running? Then you want to go by the output amp rating of the drive as it will be different from the input amp rating. The output amps is what to match to the FLA rating of the motor. The drive should be sized at the same FLA rating or higher. A drive with a lower amp rating may drive your motor, but would not drive it at its full operating capacity. If you have a drive in need of repair, whether it’s a constant torque or variable torque, call 800-732-4695 to reach the drive experts at Precision Electronic Services.