Lenze DSD Uživatelský manuál stáhnout pdf (Strana 321)

Lenze · Drive Solution Designer · Manual · DMS 4.2 EN · 12/2013 · TD23 321

11 Drive Dimensioning

11.2 Motor selection

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11.2.8 Load-matching factor

The load-matching factor is an important assessment criterion for speed- or angle controlled dy-

namic acceleration drives.

• The load-matching factor is the ratio of the load moment of inertia (reduced to the motor shaft)

to the moment of inertia of the motor:

• The load-matching factor k

is an important indicator for:

• The acceleration capability

• The control quality for speed- or angle-controlled drives

• The stability limits of the control for speed- or angle-controlled drives

•A high k

factor is uncritical for torque-controlled systems.

• With a low k

factor, the load is not very dominant and the motor has a significant effect on the

acceleration capability of the drive.

• Increasing the motor size is the wrong thing to do, as this might quickly result in making it

impossible to achieve the required dynamic performance.

• The solution for this is an increase of the gearbox ratio within the realms of possibility (ob-

serve the maximum speed for the motor and gearbox drive), or alternatively the use of low-

inertia motors (e. g. synchronous motors, 120-Hz motors).

The DSD automatically calculates the occurring load-matching factors, i.e. the mismatch of the mo-

ments of inertia.

• The calculated values are displayed and logged as preview values in the different masks and af-

ter definition of the components also as actual values.

• Depending on the application, the load-matching factor k

is fixedly determined in the DSD:

• In the case of applications with a horizontal direction of movement, k

= 20 is preset.

• In the case of applications with a vertical direction of movement (angle of tilt > 45°), k

=50

is preset.

• In the case of open-loop speed-controlled winding drives, k

= 500 is preset as limit value. The

load-matching factor is only relevant for closed-loop speed-controlled winders.

• If the load-matching factor k

< 0.5, the drive is no longer optimally adjusted.

• In this case, the motor and no longer the load is dominant (see diagram [11-6]

• For acceleration drives it is then favourable to select another ratio or a motor with low inertia.

 Note!

Load-matching factors k

< 0.5 are only unfavourable for acceleration drives, but not for

quasi-stationary drives (acceleration torques in this connection are not dominant).

• For instance in the case of drives in materials handling technology, the load-matching

factor k

can be clearly lower than 0.5. This is uncritical.

⋅

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