ABB ACS880 Series, Application Manual, Page: 17 / 44

Implementing a motor thermal protection circuit 17
One-channel connection to drive STO terminals

General
This section describes an implementation of the ATEX-compliant motor thermal protection
circuit:
•
The circuit uses the ATEX-certified Safe disconnection function (Q971) of the
drive.
•
There is a one-channel (non-redundant) connection of the motor protection relay to
the drive STO terminals. Both STO inputs of the drive are connected to same output
contact of the protection relay.
•
One output contact of the protection relay is connected to a digital input of the drive.
•
The drive shows an overtemperature indication when the digital input switches off (the
protection relay trips).
If you plan to use the one-channel (non-redundant) connection, make sure that you can
reach the necessary safety integrity level (SIL). According to EN 50495, SIL1 is sufficient
for the protection of category 2 and 3 equipment.
Note: The STO function of the drive must always have a redundant connection. See
Connection diagram on page 18 .

Resetting the safety function
A manual reset is mandatory in the temperature protection function, if it is required for
ensuring the compliance of the system with Ex/ATEX regulations. When the protection
relay detects motor overtemperature, the drive must not restart before a manual reset
command. You can implement a manual reset in the ATEX-compliant protection relay
(recommended).
In this example, you can also configure a manual reset in the drive with the motor
overtemperature or STO indication parameters (see section
Reset method and status
indications on page 24 ).

Indications of the safety function
In this example, you can use the drive STO or the motor overtemperature indication. See
section
Reset method and status indications on page 24 .
If you want to avoid parallel indications in motor overtemperature situations, you can set
one or several of the indication parameters value to
No indication (or None ) or Event :
•
the motor overtemperature indication with drive parameters 31.01...31.02 or
35.11...35.12 (see page 24 ),
•
the STO indication in the drive with drive parameter 31.22 STO indication run/stop
(see page 24 ).
Note : Make sure that at least one of these indications generates a fault if the protection
relay does not contain a manual reset.