Siemens 7SR105 Rho - Anti-Backspin (81 B); Figure 4-2 Logic Diagram: Anti-Backspin Protection (81 B)

7SR105 Rho Description of Operation
©2018 Siemens Protection Devices Chapter 1 Page 39 of 57
4.2 Anti-Backspin (81B)
Anti-backspin is used to inhibit restarting of the motor until after the rotor has completely stopped. The function
must be used in conjunction with an auxiliary switch of the motor control device which is used to indicate the open
status of the motor controller.
Anti-Backspin - Time Delay Method
When the CB is opened the ‘Anti Backspin’ DTL is started. CB closing is not allowed until the Anti-Backspin DTL
has elapsed.
Anti-Backspin – Tachometer Method
A tachometer signal that provides an output when the motor is stopped can be connected to binary input
programmed to ‘No Accel’. CB closing is not allowed until the motor has stopped.
Inhibit 81B
81B
&
≥
1
Gn 81 B Delay
No Accel
Enabled
Gn 81 B No Accel
&
Emergency Start
&
CB Open
Figure 4-2 Logic Diagram: Anti-Backspin Protection (81B)