Function Description; Design Of The Safe Shut-Down Method - nord NORDAC PRO SK 500P Series Functional Safety Manual

2 Function description

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To prevent danger to people and material it is necessary to be able to safely switch off machines. The
frequency inverters stated in this document provide safe shut-down methods.
The following basic explanation of the function of a frequency inverter serves to provide better
understanding of the function of safe shut-down methods:
The mains voltages are rectified and the resulting DC links circuit voltage is reconverted to AC
according to the requirements of the operating status of the motor (frequency and voltage).
The inverter's semiconductor switches (T1 to T6) are controlled by a complex pulse pattern. This pulse
pattern is generated by the micro-controller (µC) and amplified by the driver. The driver takes over the
conversion of the logic signals to the control voltages of the semiconductor switches. The
semiconductor switches are switched via the control voltage and the pulse pattern is amplified and
applied to the motor terminals. Due to the low-pass effect of the motor, a three-phase pulse width
modulated sine wave voltage, a three-phase system, results from the pulsed voltage. The motor
generates a torque.
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2.1 Design of the safe shut-down method

Structure of the Safe Pulse Block for SK 510P, SK 540P
BU 0630 en-0322
2 Function description
1 Safety Digital Input
2 Micro-controller
3 Driver
4 Safe Pulse Block
13