Datasheet

QSH5718-10000-AT Hardware Manual • Hardware Version V1.00 | Document Revision V1.00 • 22.02.2019

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6 Considerations for Operation

The following sections try to help you to correctly set the key operation parameters in order to get a stable

system.

6.1 Choosing the best Fitting Motor for an Application

For an optimum solution it is important to ﬁt the motor to the application and to choose the best mode of

operation. The key parameters are desired motor torque and velocity. While the motor holding torque

describes the torque at stand-still, and gives a good indication for comparing diﬀerent motors, it is not

the key parameter for the best ﬁtting motor. The required torque is a result of static load on the motor,

dynamic loads which occur during acceleration/deceleration and loads due to friction. In most applications

the load at maximum desired motor velocity is most critical, because of the reduction of motor torque

at higher velocity. While the required velocity generally is well known, the required torque often is only

roughly known. Generally, longer motors and motors with a larger diameter deliver a higher torque. But,

using the same driver voltage for the motor, the larger motor earlier looses torque when increasing motor

velocity. This means, that for a high torque at a high motor velocity, the smaller motor might be the better

ﬁtting solution.

Please refer to the torque vs. velocity diagram to determine the best ﬁtting motor, which delivers enough

torque at your desired velocities.

6.1.1 Determining the Maximum Torque Required

Try a motor which should roughly ﬁt. Take into consideration worst case conditions, i.e. minimum driver

supply voltage and minimum driver current, maximum or minimum environment temperature (whichever

is worse) and maximum friction of mechanics. Now, consider that you want to be on the safe side, and

add some 10 percent safety margin taking into account unknown degradation of mechanics and motor.

6.2 Motor Current Settings

The motor torque is proportional to the motor current as long as the current stays at a reasonable level. At

the same time, the power consumption of the motor (and driver) is proportional to the square of the motor

current. Optimally, the motor should be chosen to bring the required performance at the rated motor

current. For a short time, the motor current may be raised above this level in order to get increased torque,

but care has to be taken in order not to exceed the maximum coil temperature of 130

C respectively a

continuous motor operation temperature of 90°C.

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