Trinamic QSH5718-51-28-101 - 57 x 57mm 2-Phase Stepper Motor, 1.8 Degree, 1.01Nm, 0 - 75Vdc, 2.8A 50-0035 Fiche De Données
Codes de produits
50-0035
QSH5718 Manual (V2.3/2011-APR-12)
11
Copyright © 2011, TRINAMIC Motion Control GmbH & Co. KG
6 Considerations for operation
The following chapters try to help you to correctly set the key operation parameters in order to get a stable
system.
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 the 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 the desired velocities.
Determining the maximum torque required by your application
operation. The key parameters are the 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 the desired velocities.
Determining the maximum torque required by your application
Just try a motor with a torque 30-50% above the application’s maximum requirement. 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 to take into
account for unknown degradation of mechanics and motor. Therefore try to get a feeling for the motor
reliability at slightly increased load, especially at maximum velocity. That is also a good test to check the
operation at a velocity a little higher than the maximum application velocity.
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 to take into
account for unknown degradation of mechanics and motor. Therefore try to get a feeling for the motor
reliability at slightly increased load, especially at maximum velocity. That is also a good test to check the
operation at a velocity a little higher than the maximum application velocity.
6.2 Motor Current Setting
Basically, 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.
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.
Percentage of
rated current
Percentage of
motor torque
Percentage of static
motor power dissipation
Comment
150%
≤150%
225%
Limit operation to a few seconds
125%
125%
156%
Operation possible for a limited time
100%
100%
100%
= 2 * I
RMS_RATED
* R
COIL
Normal operation
85%
85%
72%
Normal operation
75%
75%
56%
Normal operation
50%
50%
25%
Reduced microstep exactness due to
torque reducing in the magnitude of
detent torque
torque reducing in the magnitude of
detent torque
38%
38%
14%
-“-
25%
25%
6%
-“-
0%
see detent
torque
0%
Motor might lose position if the
application’s friction is too low
application’s friction is too low
Table 6.1: Motor current settings