Allen Bradley 20-750-S4

The Allen-Bradley 20-750-S4 module is a built-in safety functions module. This module is made for the Allen-Bradley PowerFlex 755/755T drives. The 20-750-S4 module provides multiple safety functions including the networked safe torque off (STO) function, timed SS1 function, monitored SS1 function, and the safe brake control function. The module also supports controller based safety functions for Allen-Bradley GuardLogix 5580 and Compact GuardLogix 5380 controllers. The 20-750-S4 module can remove power from the circuits on the drive output devices, which leads to the disconnection of power to the motor, and it can be used with other safety devices for compliance with the IEC 61508 and other standards. Allen-Bradley recommends disconnecting the input power to the drive before the performance of any maintenance-related activity. This safety precaution will ensure that the drive output is not carrying dangerous voltages during maintenance.

Even though the STO feature on the Allen-Bradley 20-750-S4 PowerFlex 755/755T safety module disables the motor torque, mechanical forces such as back pressure or suspended loads can lead to motor rotation. Allen-Bradley does not recommend the use of the 20-750-S4 module as a control option for stopping or starting the drive regularly. The 20-750-S4 module is a current sinking module. The on-state voltage range is 11 to 30 Volts DC and the off-state voltage range is -3 to 5 Volts DC. The minimum on-state current rating is 2 milliamps and the maximum off-state current rating is 1.5 milliamps. The input reaction time for the 20-750-S4 module is less than 10 milliseconds. The module is UL approved and it is certified by numerous industrial standards that include the CE, TUV, and C-Tick standards. The host drive and the 20-750-S4 module should only be operated by trained technicians.