However, when the electric motor inertia is bigger than the load inertia, the electric motor will require more power than is otherwise essential for the particular application. This boosts costs since it requires having to pay more for a engine that’s larger than necessary, and because the increased power usage requires higher operating costs. The solution is to use a gearhead to match the inertia of the motor to the inertia of the load.
Recall that inertia is a measure of an object’s resistance to improve in its motion and is a function of the object’s mass and shape. The greater an object’s inertia, the more torque is required to accelerate or decelerate the object. This means that when the load inertia is much larger than the engine inertia, sometimes it can cause extreme overshoot or increase settling times. Both circumstances can decrease production range throughput.
Inertia Matching: Today’s servo motors are generating more torque relative to frame size. That’s because of dense copper windings, light-weight materials, and high-precision gearbox energy magnets. This creates greater inertial mismatches between servo motors and the loads they want to move. Utilizing a gearhead to better match the inertia of the motor to the inertia of the load allows for using a smaller motor and results in a far more responsive system that is easier to tune. Again, that is attained through the gearhead’s ratio, where in fact the reflected inertia of the strain to the electric motor is decreased by 1/ratio^2.
As servo technology has evolved, with manufacturers generating smaller, yet better motors, gearheads are becoming increasingly essential companions in motion control. Locating the optimum pairing must take into account many engineering considerations.
So how really does a gearhead go about providing the energy required by today’s more demanding applications? Well, that all goes back to the basics of gears and their ability to alter the magnitude or direction of an applied force.
The gears and number of teeth on each gear create a ratio. If a motor can generate 20 in-lbs. of torque, and a 10:1 ratio gearhead is mounted on its result, the resulting torque will be close to 200 in-pounds. With the ongoing emphasis on developing smaller footprints for motors and the gear that they drive, the ability to pair a smaller motor with a gearhead to attain the desired torque result is invaluable.
A motor could be rated at 2,000 rpm, but your application may just require 50 rpm. Attempting to perform the motor at 50 rpm may not be optimal predicated on the following;
If you are working at a very low quickness, such as for example 50 rpm, as well as your motor feedback resolution isn’t high enough, the update rate of the electronic drive may cause a velocity ripple in the application. For example, with a motor feedback resolution of 1 1,000 counts/rev you possess a measurable count at every 0.357 degree of shaft rotation. If the electronic drive you are employing to regulate the motor includes a velocity loop of 0.125 milliseconds, it’ll look for that measurable count at every 0.0375 degree of shaft rotation at 50 rpm (300 deg/sec). When it generally does not see that count it’ll speed up the motor rotation to think it is. At the speed that it finds the next measurable count the rpm will be too fast for the application form and the drive will slow the motor rpm back off to 50 rpm and then the whole process starts yet again. This continuous increase and reduction in rpm is what will cause velocity ripple in an application.
A servo motor operating at low rpm operates inefficiently. Eddy currents are loops of electric current that are induced within the motor during procedure. The eddy currents actually produce a drag power within the motor and will have a greater negative effect on motor functionality at lower rpms.
An off-the-shelf motor’s parameters might not be ideally suited to run at a low rpm. When an application runs the aforementioned motor at 50 rpm, essentially it is not using all of its offered rpm. Because the voltage continuous (V/Krpm) of the motor is set for an increased rpm, the torque constant (Nm/amp), which is usually directly related to it-is lower than it requires to be. As a result the application requirements more current to drive it than if the application had a motor specifically created for 50 rpm.
A gearheads ratio reduces the engine rpm, which is why gearheads are sometimes called gear reducers. Utilizing a gearhead with a 40:1 ratio, the motor rpm at the input of the gearhead will be 2,000 rpm and the rpm at the result of the gearhead will be 50 rpm. Working the electric motor at the higher rpm will permit you to avoid the problems mentioned in bullets 1 and 2. For bullet 3, it allows the look to use less torque and current from the motor based on the mechanical benefit of the gearhead.