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19 April, 2018

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Drives users are given a regen choice

01 March, 2006

Drives users are given a regen choice

Siemens will be adding several new models to its Sinamics drives family at the Hannover Fair in April. These include: a modular AC drive for high-performance, single-axis applications; a modular frequency inverter covering outputs from 0.37--90kW; and a choice of two different types of regenerative feedback.

The single-axis drive (shown above) expands the Sinamics S120 family into integrated modular drives. The modular design makes it as suitable for multi-axis applications as it is for synchronous and motion control applications. The components that provide the current infeed and the motor power supply are combined in a device known as a power module. To create a single-axis drive with a high-level controller, another module, containing closed-loop control intelligence, positioning functions and a fieldbus interface, is snapped onto the power module.

Alternatively, the drive can be connected to higher-level controls and other Sinamics 120 components by snapping a "control unit adaptor" onto the power module.

The drives will be available in single-phase 230V versions from 0.12--0.75kW and three-phase 400V versions from 0.37--250kW. Up to 90kW they have a box-type construction. Larger versions come in a chassis format.

The new G120 frequency inverters (above), which extend the Sinamics family below 100kW at voltages from 380--480V, adopt a similar format of separate control and power modules. The control modules include various analogue and digital I/O, connections for motor protection equipment, and a choice of RS-485 communications or Profibus with Profidrive 4.0. Safety control modules can be added to create Safety Integrated drives that meet Category 3/SIL2 requirements. The safety functions can be controlled either via safe digital inputs or directly via Profisafe.

The third Sinamics innovation at Hannover is to offer users a choice of two forms of regenerative feedback. The first of these, called Smart Infeed, is a basic, non-stabilised version which uses IGBTs to return the braking energy to the power system. Siemens says that the IGBTs used in the new Sinamics S120 Smart Line Modules will stand up to voltage dips better than regenerative systems that use thyristors.

If the regen system also needs to correct voltage dips, or if the quality of the regenerative current needs to be especially high, users can specify a stabilised version called Active Infeed, which supplies the connected drives with a constant voltage. High-speed vector control is said to guarantee a sinusoidal system current, while a filter minimises low-frequency perturbations.

Active Infeed is also claimed to eliminate the losses caused by harmonic currents in LV distribution systems, while the stabilised DC link voltage that isolates the motor from the system voltage, makes the drive immune from the effects of system voltage fluctuations. Users can choose the power factor.

For applications that do not need regenerative feedback, Siemens is offering users a low-cost, space-saving alternative called Basic Infeed.




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