IMO SD1 Series - Appendix D STO Function Description; D.1 STO Function Logic Table

SD1 Series Inverters STO Function DescriptionOptional Peripheral Accessories
-163-
Appendix D STO Function Description
Reference standards: IEC 61508-1, IEC 61508-2, IEC 61508-3, IEC 61508-4, IEC 62061, ISO
13849-1, and IEC 61800-5-2.
You can enable the safe torque off (STO) function to prevent unexpected startups when the
main power supply of the drive is not switched off. The STO function switches off the drive
output by turning off the drive signals to prevent unexpected startups of the motor (see the
following figure). After the STO function is enabled, you can perform some-time operations
(such as non-electrical cleaning in the lathe industry) and maintain the non-electrical
components of the device without switching off the drive.
D.1 STO Function Logic Table
The following table describes the input states and corresponding faults of the STO function.
STO input state
Corresponding fault
H1 and H2 opened
simultaneously
The STO function is triggered, and the drive
stops running.
Fault code:
40: Safe torque off (STO)
H1 and H2 closed
simultaneously
The STOP function is not triggered, and the
drive runs properly.
Control
circuit
+24V
Switch, relay, and so on
UDC+
UDC-
Drive
circuit
PWM+
PWM-
U/V/W
H1
H2
Note:
The contacts of the safety switch must be opened
or closed within 250 ms; and the cable that
connects the VFD to the safety switch cannot be
longer than 25 m.
COM