Safe Torque Off (Sto) Principle - Vacon optbj Safety Manual

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5.1

Safe Torque Off (STO) principle

The STO safety function of the OPTBJ board allows the drive output to be disabled so that the drive
cannot generate torque in the motor shaft. For STO, the OPTBJ board has two separate, galvanically
isolated inputs STO1 and STO2.
NOTE! To allow the drive to go to ready state, a voltage of +24V must be connected between the in-
put terminals for both STO input channels. See chapter 5.3.5 for details.
The STO safety function is achieved by disabling the drive modulation. The drive modulation is dis-
abled through two independent paths controlled by STO1 and STO2 so that a single fault in any of
the safety related parts will not lead to the loss of the safety function. This is done by disabling the
gate driver signal outputs to the driver electronics. The gate drive output signals control the IGBT
module. When gate drive output signals are disabled, the drive will not generate torque in the motor
shaft. See Figures 6 and 7.
Thermistor
Figure 6.STO principle with OPTBJ board and VACON
5
OPTBJ board, slot E
+
-
Atex Safety
RO
Function
STO1
STO2
Local contacts: https://www.danfoss.com/en/contact-us/contacts-list/
VACON 100 CONTROL UNIT
Control board
Atex Safety
Function
POWER UNIT
Hardware
STO 1
=
®
100 family control board MR4-10
STO and SS1 safety functions
Hardware
STO 2
3~
11575B_uk