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NTT 240/460
S.T.O. safety circuit
Installation and user guide
Rev: 4.0
Principle diagram for drive with STO safety circuit is shown below:
Interface
µ
P
PWM
Control
Opto
(6)
Power
(6)
Stop
Start
STO1
STO2
User
I/O
To
motor
Fail-safe Interface
1.
Safety function Safe Torque Off (STO)
When the two drive enable inputs STO IN 1, STO IN 2 are not connected, the drive is in a high integrity disabled
state. It will not produce torque in the motor even if internal faults are present. The drive remains active: its internal
circuits are working, parameters can be modify, signal inputs and outputs are active and it keeps communicating.
Instead, when the twoenable inputs are connected to a digital level of +24V nominal, the drive operates normally.
2.
How to use Safe Torque Off (STO)
ATTENTION!!!
Normally, drive is provided with J11 connector with bridge cables between 3-4-5 pins; in this condition, user
shall not consider the drive to be in Safe State. In order to use correctly the Safety Function STO, please take off
all bridge cables and wire external contacts.
Secure Power Disable is used in exactly the same way as a conventional enable input, so all existing applications
remain the same. In addition it disables the drive with a very high integrity, so that it can be used in safety-related
applications.
1
+24V IN
2
GND IN
3
STO IN1
+24V OUT
+24V OUT
STO IN2
4
5
1
+24V IN
2
GND IN
GND STO
3
STO IN1
+24V STO
STO IN2
4
5
J11 CONNECTOR
(
STO connection with internal supply
)
J11 CONNECTOR
(
STO connection with external supply
)
drive internal connection
It can also be used in other applications where a highly reliable disable function is required. For example, it is
common for a start/stop function to use a simple reliable contactor latch circuit in order to avoid expensive, non-
safety-related damage from inadvertent start-up. Secure Power Disable can eliminate the use of a contactor.
3.
STO does not provide motor braking
If a running drive is disabled, it immediately ends to produce torque, either motoring or braking. The motor
continue to run by its inertia untill it stops.
Содержание NTT 240
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