# SIZING AND SELECTION INDUSTRIAL DRIVE COUPLINGS ST

Symbols

 TAR Disengagement torque of the coupling (Nm) K Service factor Tmax Maximum torque of the drive system (Nm) TAN Rated torque of the motor (Nm) PDrive Drive power (kW) n Drive speed (min-1) ∝ Angular acceleration t Acceleration time (s)   1/s² JL Moment of inertia of load (kgm2) JA Moment of inertia of drive (kgm2) TAS Peak motor torque (Nm) S Number of safety elements F Tangential force (kN) r Radius to element (m) s Spindle pitch (mm) Fv Feed force (N) η Spindle efficiency d0 Pitch diameter (mm) Fv Feed force (N) CT Torsional stiffness of coupling (Nm/rad) JMasch. Total load inertia (kgm2)     (e.g. shaft + sprocket + chain + roller + 1/2 of coupling) JMot. Total driving inertia (kgm2) fe Resonant frequency of the two mass system (Hz)

## According to disengagement torque

Safety couplings are normally selected according to the required disengagement torque, which must be greater than the maximum torque required for start-up and operation.

Disengagement torque values are often determined from the drive data and are typically a multiple of the nominal torque at the operating drive speed (TAN). In addition to a start-up torque (TMAX), the following values are used as further safety factors, depending on the load conditions:

K = 1.3 uniform harmonious load
K = 1.8 heavy shock load

## According to resonant frequency

The torsional natural frequency of the coupling must be significantly higher or lower than that of the equipment. For the mechanical substitution model the two mass system applies

## According to torque

1. Calculate the drive torque TAN.

2. Base the coupling rated torque TKN on the drive torque TAN multiplied by the application factors.

## Ratings chart

Maximum torque, speed and misalignment are related and can not exist at the same time.

Evaluation T/TKN and n / nmax
Compare plotted values for combined limits.