SIEMENS 3RT2028-2BB40 Output module

Siemens offers a range of braking units, primarily associated with their SINAMICS drive systems. These units are used to dissipate excess energy generated during regenerative braking (when a motor acts as a generator, for example, during deceleration or lowering a load). This energy, if not dissipated, can cause the DC link voltage in the drive to rise excessively, leading to faults or damage to the drive.

Here's a detailed breakdown of Siemens Braking Units:

Siemens Braking Unit Overview

Siemens Braking Units are essential components in drive systems, particularly for applications involving frequent deceleration, braking, or lowering of loads. They manage the regenerative energy produced by the motor, preventing overvoltage in the drive's DC link and ensuring safe and reliable operation. These units typically consist of a braking module (also known as a braking chopper) and a braking resistor.

Product Detailed Description

• Function:

• Energy Dissipation: When a motor connected to an AC drive acts as a generator (e.g., during deceleration, stopping, or lowering a load), it feeds energy back into the drive's DC link. If this regenerative energy is not consumed by other drives on the same DC link or fed back to the grid (if using a regenerative line module), the DC link voltage will rise. The braking unit senses this voltage rise.

• Voltage Regulation: Once the DC link voltage exceeds a predefined threshold, the braking module switches on, diverting the excess energy to the connected braking resistor.

• Heat Dissipation: The braking resistor converts this electrical energy into heat, which is then dissipated into the environment. This prevents overvoltage trips in the drive and allows for rapid deceleration or controlled braking.

• Components:

• Braking Module (Braking Chopper): An electronic power component that monitors the DC link voltage. When the voltage exceeds a set limit, it rapidly switches to connect the braking resistor across the DC link.

• Braking Resistor: A passive component designed to convert electrical energy into heat. These resistors are typically robust, high-power resistors built to handle significant transient power dissipation.

• Types:

• Integrated Braking Units: Some smaller SINAMICS drives (e.g., certain SINAMICS G120C, PM240-2 modules) have an integrated braking chopper, requiring only an external braking resistor.

• External Braking Modules: For larger drives or applications with higher braking power requirements, separate braking modules are used, which are connected to the drive's DC link and an external braking resistor.

• Braking Resistors: These are the components that actually dissipate the energy as heat. They come in various power ratings and resistance values to match the application's braking energy and duty cycle requirements.

Product Parameters

Since Siemens offers a wide range of braking units for different SINAMICS series (e.g., SINAMICS G120, S120, S150), specific parameters vary greatly. However, here are common parameters you'll encounter:

• Input Voltage: Matches the DC link voltage of the drive (e.g., 600V DC, 860V DC, 1035V DC).

• Braking Power:

• Continuous Power (P_cont): The maximum power the unit can continuously dissipate.

• Peak Power (P_peak): The maximum power the unit can dissipate for a short duration (e.g., for 15 seconds, 20 seconds), often expressed with a duty cycle (e.g., 150 kW / 15s for 240s cycle).

• Resistance Value (for braking resistors): Specified in Ohms (Ω), matched to the braking module.

• Protection Class (IP): E.g., IP20 (for controlled environments), IP54, IP65 (for harsh environments).

• Ambient Temperature Range: E.g., -25 °C to +40 °C.

• Cooling Method: Air-cooled (natural convection or forced ventilation).

• Connection Type: Terminal blocks for connecting to the DC link and braking resistor.

• Compatibility: Designed for specific SINAMICS drive series and power modules.

• Monitoring Functions: Some braking modules may offer thermostatic switch connections for monitoring resistor temperature.

Product Advantages

• Enhanced Drive Protection: Prevents overvoltage damage to the drive's DC link, extending its lifespan.

• Reliable Braking Performance: Ensures controlled and repeatable deceleration, even with high inertial loads.

• Increased Productivity: Allows for faster cycle times by enabling rapid deceleration.

• Energy Management: Efficiently dissipates excess energy, preventing it from causing issues.

• Robust Design: Built for industrial environments, ensuring durability and long-term operation.

• Integration with SINAMICS: Seamlessly integrates with Siemens' comprehensive SINAMICS drive portfolio, leveraging advanced control functionalities.

• Scalability: Available in a wide range of power ratings to match various application requirements.

Precautions

• Correct Sizing: It is crucial to correctly size the braking module and resistor based on the application's regenerative energy, braking duty cycle, and the drive's power. Incorrect sizing can lead to overheating, poor braking performance, or drive faults.

• Proper Installation:

• Install braking resistors in a well-ventilated area, away from heat-sensitive components, as they generate significant heat.

• Ensure proper clearances for cooling.

• Follow Siemens' detailed wiring diagrams and instructions for connecting the braking module to the drive's DC link and the resistor.

• Use appropriate cable cross-sections and observe maximum cable lengths.

• Electrical Safety:

• High DC link voltages are present; only qualified personnel should install, commission, and maintain these units.

• Ensure proper grounding.

• Implement lockout/tagout procedures before working on the equipment.

• Thermal Management:

• Monitor the temperature of braking resistors, especially for heavy-duty applications. Some resistors have integrated thermal switches that should be connected to the drive's control system.

• Duty Cycle: Adhere strictly to the specified duty cycle for peak power dissipation to prevent overheating and damage to the resistor.

• Compatibility: Always ensure the braking unit is compatible with your specific SINAMICS drive model.

Product Applications

Siemens Braking Units are commonly found in applications where motors frequently operate in regenerative mode, including:

• Hoisting and Lifting Equipment: Cranes, elevators, hoists, and escalators, where heavy loads are lowered.

• Conveyors: Conveyor belts with inclines or where quick stops are required.

• Centrifuges: Applications requiring rapid deceleration from high speeds.

• Machine Tools: Spindles and axes that undergo frequent acceleration and deceleration cycles.

• Test Benches: For simulating loads and braking conditions.

• Wind Turbines (Pitch Systems): Though less common for main power generation, braking resistors might be used in pitch control systems for rapid blade angle adjustments.

• Textile Machinery: High-speed spinning and winding machines that require quick stops.

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