Regenerative feedback with SINAMICS G120 and SINAMICS G120D

With its Efficient Infeed Technology, Siemens AG is setting a global standard for drives of compact design. The technology applied is a world first and provides regenerative feedback capability in smaller, lighter and much lower-cost inverter units.

Available drives with Efficient Infeed Technology

The following drives are equipped with Efficient Infeed Technology:

• SINAMICS G120 (integrated in PM250 Power Modules)
• SINAMICS G120D
• SIMATIC ET 200pro FC-2

Potential savings thanks to Efficient Infeed Technology

The table below shows the advantages of the technology as compared to conventional 2-quadrant inverters.

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Three technical criteria are of particular significance:

• Regenerative feedback
  • 100 % braking power is fed back, allowing continuous braking. This is possible using braking resistors which take up a lot of space and are expensive.
  • A braking resistor does not need to be configured.
  • No need for installation, thermal monitoring, etc. of external components.
• Minimal reactive power distortion
  • Low reactive power distortion thanks to current consumption that is almost block-shaped, the power factor λ is virtually 0.9. The transformer throughput rating is therefore lower than that required for inverters with a standard DC .
  • In order to achieve such a low harmonic content (line harmonics) for an inverter with a conventional DC , a line reactor with a u_K = 6 % is required.
  • This results in approx. 22 % lower current consumption which corresponds to approximately 40 % lower losses in the supply system.
  • The load on the power supply system is therefore reduced.
• Improved offset factor cos φ
  • Slightly capacitive at input ≅ 0.95 capacitive.
  • Compensates the reactive power of motors and other inductive loads on the same supply.
  • The power draw of the entire system is reduced. In a system comprising one inverter with motor and another motor on the same supply, the total power draw is reduced by up to 12 %.

Line supply conditions

Inverters with Efficient Infeed Technology have a much lower harmonic content (and therefore lower reactive current component) than a standard inverter. The harmonics up to and including the 11th harmonic are significantly lower than specified in the standard. These relevant harmonics are less than half the magnitude stipulated by the relevant standard (EN 61000‑3‑12).

Permissible ratio between network short-circuit power S_{K_line} and inverter apparent power S_inverter:

S_{K_line} ≥ 100 × S_inverter according to u_K ≤ 1 %

• Continuous braking with 100 % braking power
• Energy savings through regenerative feedback with motor operating in generator mode
• Omission of braking resistor, line reactor and brake chopper
• No costly configuration of the braking resistors and no time-consuming cabling
• Requires considerably less space than a conventional compact inverter
• Power supply requirements reduced by up to 22 %
• No additional heat generated during braking
• Cost savings
• Space savings

Whenever an application involves movements with frequent changes in speed or rotational direction or requires masses to be electrically braked, inverters with regenerative feedback capability are an attractive drive solution for both operating companies and machine manufacturers.

This is also true for applications with vertical motion generally, or for driven loads with a high moment of inertia:

• Drives for conveyor vehicles
• Stage machinery in theaters
• Cranes
• Heavy load transport systems/conveyors
• Storage and retrieval machines
• Centrifuges
• Brake testing systems
• Drum-type crushers/revolving screens
• Vertical load hoists
• Industrial washing machines
• Shuttles/elevator systems/endless bucket belts
• Rolling mills/conveyor belts
• Winding machines

Generally, for applications with a high braking power over long periods of time, in many cases it makes sense to use Efficient Infeed Technology - this reduces the costs and the amount of space required.

SINAMICS infeed concepts

SINAMICS offers four design concepts for the converter/inverter infeed circuit.

Concept	Characteristic features
Basic Infeed (only for multi-axis drives)	Automatic energy exchange via the common DC during infeed with Basic Line Module infeed unit No regenerative feedback capability Braking resistor required for braking operation High harmonic content (reactor available as option) Efficiency approx. 99 %
Smart Infeed (only for multi-axis drives)	Automatic energy exchange via the common DC Regenerative feedback capability Line reactor is required Efficiency approx. 98 % to 99 %
Efficient Infeed	Regenerative feedback capability Line reactor not required/not permitted Low harmonic component Efficiency approx. 98 % High energy efficiency and high active current component
Active Infeed (only for multi-axis drives)	Automatic energy exchange via the common DC Regenerative feedback capability Low harmonics in motor and generator operation Efficiency approx. 97 % to 98 % Operation on island networks possible Operation on weak networks possible (uK  ≤ 5 %) Boosting DC voltage permits smaller power units Decoupling from line voltage fluctuations due to constantly controlled DC voltage