NORD Drivesystems BU0530 - Manual (Page 21)

2 Description of function
BU 0530 GB-3712 21
2.1 Safe shut-down method
With the aid of a safe shut-down method the torque is now to be safely shut down. This corresponds to the
safety function STO (safe torque off).
In order to switch off the torque, the current to the motor must be interrupted. The pulse block is provided for
this.
NOTE
On triggering the safe shut-down method, a mechanical brake connected to the terminals 1
(K1.1) and 2 (K1.2) can be applied (see parameter 434 in the BU 0500 GB manual). If the
drive unit is not previously switched off, the brake must be designed as an operational brake.
2.1.1 Safe pulse block
Devices equipped with a "safe pulse block" have an additional DC/DC converter, which produces the supply
voltage for the driver from a 24V supply (24V_SH, GND_SH).
If the external 24 V voltage is switched off then the DC/DC converter does not transmit any power to the
drivers. As the drivers are now no longer supplied with power, no control pulses reach the relevant
semiconductor switches of the inverter. The flow of current in the semiconductor switches and the motor is
interrupted. I.e. after a certain reaction time of the electronics and the reduction time of the motor current, the
motor does not develop a driving torque.
The switch-off of the 24V supply (24V_SH, GND_SH) must be carried out by a fail-safe switching device. For
this, either the connection 24V_SH (Terminal 89) or the connection GND_SH (Terminal 88) may be
disconnected from the 24V source. For preference, the 24V_SH connection is disconnected.
2.1.2 Digital inputs
In order to implement a safety function, the digital inputs can be used as auxiliary inputs, e.g. for the triggering
of a braking process. It should be noted that the digital inputs only fulfil minimum safety requirements. A safe
shut-down method is always required!
The digital inputs, other I/Os and the 24V supply have a common earth. This means that a digital input may
only be switched off by disconnecting the associated connection (21 for DIN1 to 24 for DIN 4). Switch-off via
GND is not possible!
When operating with an OSSD
1
a filter is only required for environments with strong interference.
If only low levels of functional safety are required, the safety function can also be implemented with the digital
inputs. It is recommended that this is only considered if the risk assessment has shown that slight (normally
temporary) injuries could result on failure of the safety function (see also Section 6 ). In case of doubt, a safe
shut-down method should always be used.
1
Output Signal Switching Device
DIN1 ...
GND
DIN4
Frequency inverter
Filter
for
OSSD
optional
21
40
24V
Safety output
Safety output
24V
24
Safety output
24V
GND SH
24V SH
Frequency inverter
88
89
Safety output
24V
or
Safety output
24V
or
Safety output
24V