WEG CFW-11 User Manual - page 67

Installation and Connection

3

CFW-11 | 3-41

3.3.2 Operation

3.3.2.1 Truth Table

Table 3.11 - Safety Stop function operation

STO1 Logic Level

(Voltage Between

XC25:1-2

Terminals)

STO2 Logic Level

(Voltage Between

XC25:3-4

Terminals)

Safety

Stop

Function

Inverter Behavior

0 (0 V)

0 (0 V)

Activated

(enabled)

Inverter remains in STO state and does not accept commands. In order to escape 

this condition, it’s required to have STO1 = 1 and STO2 = 1 simultaneously

0 (0 V)

1 (24 V)

Fault

Inverter is tripped by F160 fault (Safety Stop function related fault). To 1 (24 V) 

0 (0 V) escape this condition, it’s required to reset the inverter

1 (24 V)

0 (0 V)

1 (24 V)

1 (24 V)

Disabled

Inverter accepts commands normally

 NOTE!

Maximum delay between STO1 and STO2 signals: 100 ms (otherwise inverter will be tripped by 

F160 fault).

Safety Stop function takes priority over all other functions of the inverter.

This function should not be used as a control for starting and/or stopping the inverter.

3.3.2.2 State of Inverter, Fault and Alarm Related to Safety Stop Function

Table 3.12 - State of inverter, fault and alarm related to Safety Stop function

State / Fault / Alarm

Description

Cause

STO state

Safety Stop activated

Voltage between terminals 1 and 2 (relay K1 coil) and between terminals 3 and 

4 (relay K2 coil) of XC25 lower than 17 V

F160 fault 

Safety Stop function

fault

It’s applied voltage to relay K1 coil (STO1) but it’s not applied voltage to relay 

K2 coil (STO2) or vice-versa or there is a delay of more than 100 ms between 

one signal and the other. To solve it, correct the external circuit that generates 

STO1 and STO2 signals

3.3.2.3 STO Status Indication

State of the inverter is shown on the left upper side of the display and in parameter P0006.

Possible states of the inverter: ready, run (inverter enabled), undervoltage, fault, self-tuning, configuration, DC

braking and STO (Safety Stop function activated).

It’s possible to set one or more digital and relay outputs of the inverter to indicate that Safety Stop function is 

activated (state of the inverter = STO), if the inverter is or not on a fault state and more specifically if the inverter

was tripped by F160 fault (Safety Stop function fault). For that use the parameters P0275 (DO1), P0276 (DO2),

P0277 (DO3), P0278 (DO4) and P0279 (DO5) according to 

Table 3.13 on page 3-42

.