Open topic with navigation

Hardware enable

The controllers support the "STO" (Safe Torque Off) safety function in accordance with the requirements of EN 61800-5-2, EN ISO 13849-1 "PLe"

and EN 61508 / EN 62061 "SIL 3". The safety function "STO" to EN 61800-5-2 describes a safety measure in the form of an interlock or control function. "Category 3" signifies that the safety function will remain in place in the event of a single fault.
The connected control signals "ISDSH" and "ENPO" must always be tested by the operator or a higher-level PLC for plausibility relative to the feedback (RSH). The occurrence of an implausible status is a sign of a system error (installation or servocontroller). In this case the drive must be switched off and the error rectified.

The safety-related parts must operate in such a way that:

• a single fault in any of the said parts does not result in loss of the safety function;
• the single fault is detected on or before the next request to the safety function.
  
  

For the "STO" function the servocontrollers are equipped with additional logic circuits and a feedback contact (terminal RSH on X4). The logic cuts the power supply to the pulse amplifiers to activate the power stage. In combination with the controller enable "ENPO" the system uses two channels to prevent the motor creating a torque.

Testing the STO function

Function testing: The STO function (protection against unexpected starting) must essentially be checked to ensure it is operative:

• during initial commissioning;
• after any modification of the system wiring;
• after replacing one or more items of system equipment.
• Cancelling one of the two signals "ISDSH" or "ENPO" disables the control and the motor runs down unregulated.
  
  
  

Hardware enable or Autostart

The input "ENPO" is reserved for the hardware enable.

At the setting "OFF" the digital input signal "ENPO" is used merely for safe shutdown of the drive and as protection against switching on.
With the setting "START" in combination with parameter
P 0144 DRVCOM AUTO_START = "LEVEL" autostart mode is activated only in ServoOne.
With "STO active" activating the "ENPO" is sufficient to start control of the drive. When the "ENPO" is cancelled the drive runs down uncontrolled.
If the switch-on delay is active, the power stage starts when the preset timer has elapsed.
The setting for the ENPO can be found in the "Digital inputs" dialog box.

Bild: Hardware enable – power stage with ENPO

NOTE: The plausibility between input signals (ENPO, ISDSH) and feedback (RSH) must always be monitored.