Integrated drive portfolio:

The core elements of a fully integrated drive system are frequency converters, motors, couplings and gear units. Siemens offers all the required components in top manufacturing quality from a single source, perfectly integrated – operating perfectly together, for all performance classes.

As a standard solution or tailored to individual requirements. No other provider on the market is able to offer a comparable portfolio. All Siemens drive components are optimally tuned to each other so that they interact ideally in every application.

Siemens Integrated Drive Systems turn simple drive components into real systems. Drive technology based on IDS ensures maximum productivity, energy efficiency and reliability in every automation environment and over the entire product lifecycle.

FLENDER couplings – Part of the drive system

A drive system comprises individual machines, including the motor and gear unit. Couplings combine these components and frequently also establish the connection to the driven machine.

The coupling can perform other tasks in addition to the transmission of rotary motion and torque, such as::

• Compensation for shaft misalignment with low restorative forces
• Influencing of intrinsic torsional frequency and damping
• Overload: interruption or limitation of torque
• Electrical insulation, noise insulation
• Function in explosive environments

Couplings are frequently planned after the machines to be connected have already been selected. Thanks to a large number of different coupling assembly options, specified boundary conditions for installation space and connection geometry can be met from the catalog standard. The coupling also performs secondary functions, such as the provision of the brake disk or brake drum for operational or holding brakes, devices to record speed or the addition of chain wheels or belt pulleys.

Because of the environment, the coupling has to meet a large number of additional requirements. Couplings must be as suitable for use in a potentially explosive environment as for use at a high or low ambient temperature. The environment may be defined as chemically aggressive or be subject to laboratory conditions or requirements of food manufacture.

Standard construction types of Siemens FLENDER couplings forSIMOTICS FD motors

Shaft misalignment

Shaft misalignment is the result of displacement that occurs during assembly and operation and, where machines constructed with two radial bearings each rigidly coupled, will cause high loads being placed on the bearings. Elastic deformation of base frame, foundation and machine housing will lead to shaft misalignment which cannot be prevented, even by precise alignment. Furthermore, because individual components of the drive train heat up differently during operation, heat expansion of the machine housings causes shaft misalignment.

Poorly aligned drives are often the cause of seal, rolling bearing or coupling failure. Alignment should be carried out carefully by specialist personnel in accordance with the Siemens operating instructions.

Depending on the direction of the effective shaft misalignment, a distinction is made between:

The couplings can be subdivided into the following groups:

• Single-joint couplings – N-EUPEX and RUPEX series
  Couplings with flexible elements mainly made of elastomer materials. Shaft misalignment results in deformation of the elastomer elements. The elastomer elements can absorb shaft misalignment as deformations in an axial, radial and angular direction. The degree of permissible misalignment depends on the coupling size, the speed of rotation and the type of elastomer element. Single-joint couplings do not require an adapter and are therefore short versions.

Example: RUPEX coupling

• Two-joint couplings – ARPEX and ZAPEX series
  Two-joint couplings are always designed with an adapter. The two joint levels are able to absorb axial and angular misalignment. Radial misalignment occurs via the gap between the two joint levels and the angular displacement of the joint levels. The permitted angular misalignment per joint level is frequently about 0.5°. The permitted shaft misalignment of the coupling can be adjusted via the length of the adapter. If there are more than two joint levels, it is not possible to define the position of the coupling parts relative to the axis of rotation. (The less frequently used parallel-crank couplings are an exception).

Example: ARPEX coupling

Overload

Overload conditions are operating conditions that go beyond the limit loads of the coupling. Overload conditions may occur under non-standard operating conditions, e.g. drive blockage, short circuit or supply fluctuations, as well as under standard operating conditions, e.g. when starting or braking. Particularly in the case of high mass moments of inertia of the driven machine, torques that are a multiple of the motor starting torque may become effective during direct starting or star-delta starting.

Overload conditions may damage not only the coupling but also the entire drive train. Overload conditions can frequently be prevented with special design measures. SIRIUS soft starters or SINAMICS frequency converters are suitable for considerably reducing starting torques of induction motors. If drive blockages or overloads of the driven machine cannot be ruled out, torque limiting SECUREX couplings can prevent damage to the drive train.

Coupling behavior under overload conditions

Coupling behavior under overload where the torque is considerably above the limits of use of the coupling concerned is determined by the engineering design of the coupling series.

The ZAPEX, ARPEX, N-EUPEX and RUPEX coupling series can withstand overloads until the breakage of metal parts. These coupling series are designated as fail-safe. Coupling types which can withstand overload, i.e. fail-safe types, are used e.g. in crane systems. In case of coupling breakage due to overloads, the splintering metal parts may cause injury to persons and property damage!

The N-EUPEX DS coupling series throws overload. The elastomer element of these couplings is irreparably damaged without damage to metal parts when subjected to excessive overload. These coupling series are designated as non-fail-safe. The types that fail can be fitted with a fail-safe device. This component enables emergency operation, even after the rubber element of the coupling has been irreparably damaged..

Damping

On drives which are prone to torsional and bending vibrations, measurements or calculations such as natural frequency calculations, torsional vibration simulation or bending vibration calculations are necessary for verifying safe dimensioning of the drive train and preventing damage.

The drive train may, depending on complexity, be regarded as a two-mass vibration-generating system or N-mass vibration-generating system. The vibration-generating masses are defined by the rotating bodies and the couplings by the coupling stiffnesses and shaft stiffnesses. The effect of torsional vibration excitations on the behavior of the system is calculated.

Torsional vibration excitations may occur during the starting of an induction motor, during a motor short circuit or in diesel engine drives. Bending vibrations may be critical if the coupling is insufficiently balanced and/or at an operating speed close to the critical speed.

The details needed for calculating the torsional vibration are specified in the coupling catalog:

• Dynamic torsional stiffness
• Damping (specification of the damping coefficient ? or Lehr'sdamping D = ?/4?)
• Mass moment of inertia of the coupling halves

Electrical insulation

A particularly efficient and economical measure for reducing bearing currents is to use an electrically isolating coupling. The range of couplings comprises suitable couplings in leakage-current-isolated versions for the various drive scenarios.

Version for potentially explosive atmospheres

Wherever a potentially explosive environment cannot be ruled out, the machinery used must meet special conditions in order to prevent the outbreak of fire as far as possible. Within the European Union, Directive 94/9/EC applies to these applications. This directive, also called ATEX 95, harmonizes the individual states' legal requirements for explosion prevention and clearly defines the procedure for testing and circulating machines and parts.

Whether or not a machine is used in a potentially explosive environment, the manufacturer is required under EC Machinery Directive 98/37/EC to assess and as far as possible prevent hazards which may arise from his product.

The operator has an obligation to ascertain whether an environment is potentially explosive. Details of this are laid down in Directive 1999/92/EC, also known as ATEX 137. The manufacturer is responsible for ensuring that the product is safe as defined in the EC Machinery Directive and conforms to Directive 94/9/EC if the EX requirement is specified by the operator.

The drive train mostly comprises individual pieces of equipment which are put together to form a subassembly. If the individual pieces of equipment, such as motor, coupling, gear unit or driven machine, conform to Directive 94/9/EC, the manufacturer of the overall unit can limit the risk assessment to the additional hazards which arise from the combination of different individual pieces of equipment. The hazards which can arise from the individual pieces of equipment are assessed by the relevant suppliers.

The coupling series suitable for use in potentially explosive environments are marked EX in Catalog MD 10.1.

FLENDER couplings are to be rated as components according to the new EC Machinery Directive 2006/42/EC. Therefore, Siemens does not issue a declaration of incorporation for these products.

Assignment of coupling types to SIMOTICS FD motors

For further information on FLENDER couplings, see Catalog MD 10.1.