Behavior Of Holding Brake; Safety Certification; Implementation In Control Systems - Danfoss VLT Safety Option MCB 150 Installation Manual

Installation Guide | VLT® Safety Option MCB 150/151
• Removed the power to the motor.
• Switches the motor to torque-free if Safe Torque Off is activated.
The safe control system:
• Activates the safety functions via inputs on the safety option.
• Evaluates signals from safety devices, such as:
- E-STOP push buttons.
- Non-contact magnetic switch.
- Interlocking switch.
- Light curtain devices.
• Processes the safety option status function.
• Provides safe connection between safety option and safety control system.
• Provides fault detection at activation of safety functions (shorts across contact, short circuit) on signal between the safety control
system and the safety option.

3.1.1 Behavior of Holding Brake

RISK OF HAZARD
External forces acting on the motor (vertical axis) and unwanted movements, for example caused by gravity, can cause hazards
leading to death or serious injury.
Add measures for fall protection before operating the motor.
-
Triggering the Safe Torque Off safety function means that the delay time for motors with holding brake is not effective. The motor
cannot generate holding torque to bridge the time to application of the holding brake. Check whether more measures have to be
taken, for example, this may cause the load of vertical axes to lower.

3.1.2 Safety Certification

The safety option is certified for use in safety applications up to and including SIL 2 according to EN IEC 61508 and EN IEC 62061,
Performance Level PL d, and Category 3 according to EN ISO 13849-1. Safety requirements are based on the standards valid at the time
of certification. The IFA (Institute for Occupational Safety & Health) has approved the safety option for use in safety-related applications
where the de-energized state is considered to be the safe state. All examples related to I/O included in this manual are based on
achieving de-energization as the safe state.

3.1.3 Implementation in Control Systems

Often, design measures are not sufficient and protective devices are required to minimize the risk. In this context, safety functions
executed by SRP/CS (safety-related part of control systems) are defined. SRP/CS includes the entire safety chain with sensor (detect),
logic (process), and actuator (switch).
Safety functions are defined based on the application and the hazard. They are often specified in a Type C standard (a product
standard), which provides precise specifications for special machines. If a C standard is not available, the machine designer defines the
safety functions. Typical safety functions are described in more detail in EN ISO 13849-1, section 5, Specification of Safety Functions.
The safety functions for drive systems are described in IEC 61800-5-2.
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Functions and Systems Overview
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