Nord-drivesystems BU0530 User Manual download pdf (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

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.

Output Signal Switching Device

DIN1 ...

GND

DIN4

Frequency inverter

Filter

for

OSSD

optional

24V

Safety output

24V

Safety output

24V

GND SH

24V SH

Frequency inverter

Safety output

24V

Safety output

24V

Safety output

24V

1 2 ... 16 17 18 19 20 21 22 23 24 25 26 ... 55 56

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Nord-drivesystems BU0530 User Manual Page 21

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