Vacon OPTAF, User Manual

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STO AND SS1 SAFETY FUNCTIONS vacon • 15
Local contacts: https://www.danfoss.com/en/contact-us/contacts-list/
3.1 Safe Torque Off (STO) principle
The STO safety function of the OPTAF board allows the drive output to be disabled so that the drive
cannot generate torque in the motor shaft. For STO, the OPTAF board has two separate, galvanically
isolated inputs SD1 and SD2.
NOTE! Both SD1 and SD2 inputs are normally closed for the drive to be in enable state.
The STO safety function is achieved by disabling the drive modulation. The drive modulation is dis-
abled through two independent paths controlled by SD1 and SD2 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 mod-
ule. When gate drive output signals are disabled, the drive will not generate torque in the motor
shaft. See Figure 3.
In larger drives, the STO functionality extends to the power unit. See Figure 4.
If either of the STO inputs is not connected to a +24 V signal, the drive will not go to the RUN state.
Figure 3. STO safety function principle in VACON
®
NXP AC drive with the OPTAF board
SD1+
+
SD1-
SD2+
SD2-
-
RO1/3
RO1/1
RO1/2
RO2/3
RO2/2
M
=
3~
NXP CONTROL UNIT
Control board
OPTAF board, slot B
POWER UNIT
Hardware
STO 1
PWM
control
Thermistor
Hardware
STO 2
Atex Safety
Function
Relays only for operational use,
not part of the safety functions
11053.eps
PWM
control
Control
logic