Summa Series Servodrive Product Manual
STO
Document Version: V1.01
(Dec, 2019)
© 2019 ESTUN Automation Co., Ltd. All right reserved.
11-1
Chapter 11
STO
11.1
Introduction
This product has the integrated safety function
Safe Torque Off
(STO) according to IEC 61800-5-2,
which is equivalent to an uncontrolled stop in accordance with stop category 0 of IEC 60204-1, which can
protect people from dangerous movements of the machine and reduce the risk of operator.
The safe torque off (STO) function is a safety function that shuts the Motor current and turns off Motor
output torque by turning off the driving signal of the Drive’s internal power transistor, when safety input
signal is detected.
However, the safety function STO is not equivalent to the safety function
safe off
of IEC 60204-1, since it
does not provide any galvanic insulation. This means that the Motor terminals can still have dangerous
voltage when in STO state.
Block Diagram
The circuit diagram of safety function is as shown in Figure 11-1.
Figure 11-1
Circuit diagram of safety function
Servodrive
0V
Switch
24V Power Supply
Cutoff
Cutoff
DSP
PWM
Inverter
module
Power
Supply
Motor
CN6
HWBB1+
HWBB1-
HWBB2+
HWBB2-
Close the Switch for turning ON HWBB1 and HWBB2, PWM signal can be allowed to pass by Cutoff circuit, which
is, allowing the torque to output.
Open the Switch for turning OFF HWBB1 or HWBB2, PWM signal cannot be allowed to pass by Cutoff circuit,
which is, forbidding the torque to output.
The reliability block diagram of safety function is as shown in Figure 11-2.
