F6 Drive Functional Safety for Industrial Machinery

Industrial machinery has become increasingly powerful and complex. These increased risks can pose hazards for people and the environment. The KEB F6 variable frequency drive utilizes specific safety functions that can help minimize the risks that may arise from the increased power and functionality of today’s modern industrial machinery.

Functional safety provides a basis for protecting people and environments to minimize the potential risks the machine design poses.

The certified functional safety options in the F6 drive system, provides a component to achieve a functionally safe system solution for machines and plants. Safety functions are based on a consistent architecture which may result in potential space, time, and cost savings.

The following bullet points outline essential F6 safety functionality:

• All safety functions for applications up to SIL3 according to IEC 61508 or to PLe according to ISO 13849
• Speed-dependent safety functions with resolver or certified safe Sin/Cos encoder
• Control via safe digital inputs
• Control via Safety over EtherCAT (FSoE)
• Ripple function for composition of a simple ring structure
• 2-channel clock pulse output for potential-free supply to safety inputs
• Safe parameter-setting via safety module – Editor in KEB COMBIVIS 6 Software
• Different password levels enable stepped user access
• Transfer of settings via parameter download (also from control)

The KEB F6 offers many safety functions built into the control system of the VFD. Depending on the safety function required, KEB provides multiple safety module (SM) options. Below is a general description of the safety functions available and which safety module is required to implement the function.

Overview Safety Charts  

The next few charts give an overview of KEB’s generation 6 safety modules in categories ranging from hardware to safety profiles. These charts can be used as a quick reference to help you decide which Safety module (SM) is best for your machine application. After these overview comparison charts you can scroll down to more specific information on KEB safety functions and what they mean with speed and torque profile graphs to help you better understand how they relate to machine safety.

Safety Module Chart – Overview

Below is an overview of safety features available in the different F6 Safety Modules (SM), looking at the main topics of FSoE, controlled terminal blocks, functional range, and the two KEB safety types.

Safety Module Hardware Chart

The chart below higlights the hardware characteristics of KEB Safety Modules (SM) on the F6 drive.

Basic Safety Module Profiles

Below is an overview of basic safety profiles available with different Safety Modules, from Safe Torque Off (STO) to Safe Speed Monitoring (SSM).

Safe Speed Profile Overview

This chart highlights the safe speed profiles available in each of the F6 Safety Modules (SM).

Safe Position Modules

These safe position profiles are available in the following F6 Safety Modules (SM).

Safe Torque Modules

The chart below shows safe torque profiles are available in the following F6 Safety Modules (SM).

KEB Safety Functions – Specific Profile Breakdown

Safe Torque Off (STO)

STO works to cut torque at the motor shaft.

Safe Brake Control (SBC)

SBC applies safe external supply on a spring-operated brake to bring the motion of a machine to a stop.

Safe Stop 1 – Type B (SS1-B)

A VFD decelerates the load and the ramp is monitored after the function is triggered until the motor has no torque.

Safe Stop 1 – Type C (SS1-C)

Similar to the graph above, the drive decelerates the load, but does not monitor the deceleration ramp until the motor has no torque.

Safe Stop 2 – Type B (SS2-B)

The drive decelerates the load and then enables Safe Operating Stop (SOS) with motor torque applied to maintain stop position.

SSM / f=0Hz 

This function gives a safe output signal if the drive stands still only in v/f-Modus or ASCL. No safe encoder needed, and it is no standard safety function in EN 61800-5-2.

Safe Operating Stop (SOS)

The function monitors whether the drive remains in standstill and in defined position window. If the actual position deviates, an error is triggered and the function set to STO.

Safe Limited Speed (SLS)

SLS ensures that the drive does not exceed a maximum speed. When exceeding the adjusted maximum speed, this error function executes STO or SS1.

Safe Speed Range (SSR)

The function ensures that the drive does not exceed a maximum and minimum speed. When exceeding the adjusted maximum or minimum speed, this error function executes STO or SS1.

Safe Speed Monitor (SSM)

This function delivers an output signal to indicate if the motor speed is below a predefined limit. SSM triggers no reaction in the module. The reaction must be generated by an external module.

Safe Direction (SDI)

This function ensures that the drive shaft maintains a parameterized direction of rotation. If the defined direction of rotation of the drive is not met, an error function is activated which triggers the function STO or SS1.

Safe Maximum Speed (SMS)

SMS works like SLS but is always active and needs no activation by input or FSoE.

Safe Zero Monitoring (SZM)

This function delivers an output signal to indicate if the motor speed is zero. SZM triggers no reaction in the module. The reaction must be generated by an external module.

Safe Limited Acceleration (SLA)

This function ensures that the motor shaft does not exceed a defined acceleration. This function requires a safe encoder.

Safe Acceleration Range (SAR)

SAR ensures that the drive does not exceed a maximum and minimum acceleration. When exceeding the adjusted maximum or minimum acceleration, this error function executes STO or SS1.

Safe Limited Position (SLP)

The function ensures that the drive shaft does not exceed the parameterized absolute position limits. SRX is similar by setting the reference position for the safety function “safe limited position (SLP)”.

Safe Emergency Limits (SEL) 

The SEL function is a variance of Safe Limited Position (SLP). It limits the maximum speed depending on the stopping distance.

Safe Limited Increments (SLI)

The function monitors whether the motor shaft exceed defined increments. The activation of an input configured with the function SLI of the safety module first activates the SOS function. A safe encoder is required.

Safe CAM (SCA)

The facilitates the monitoring of a position range. Signals the status with no error response.

Safe Maximum Position (SMP)

The SMP function works like SLP but is always active and needs no activation by input or FSoE.

Safe Limited Torque (SLT)

The function ensures that the drive does not exceed a maximum torque. When exceeding the adjusted maximum torque, this error function executes STO or SS1.

Safe Torque Range (STR)

The function ensures that the drive does not exceed a maximum and minimum torque. When exceeding the adjusted maximum or minimum torque, this error function executes STO or SS1.

Safe Maximum Torque (SMT)

The SMT function works like SLT but is always active and needs no activation by input or FSoE.

Safe Torque Monitoring (STM)

This function delivers an output signal to indicate if the motor torque is below a predefined limit. STM triggers no reaction in the module. The reaction must be generated by an external module.

Conclusion

The sixth generation of KEB drives offer scalable safety functions directly in the drive controller. The COMBIVERT F6 VFD offers selectable functions according to the requirements of your machine. For more information about safety features and KEB automation products contact us today.