Planning the electrical installation
49
Prevention of unexpected start-up
The ACS800-07/U7 drives can be equipped with an optional Prevention of
unexpected start-up function (POUS) according to standards IEC/EN 60204-1:1997;
ISO/DIS 14118:2000 and EN 1037:1996.
The Prevention of unexpected start-up function disables the control voltage of the
power semiconductors, thus preventing the inverter from generating the AC voltage
required to rotate the motor. By using this function, short-time operations (like
cleaning) and/or maintenance work on non-electrical parts of the machinery can be
performed without switching off the AC power supply to the drive.
The operator activates the Prevention of unexpected start-up function by opening a
switch on a control desk. An indicating lamp on the control desk will light, signalling
that the prevention is active. The switch can be locked out.
The user must install on a control desk near the machinery:
• switching/disconnecting device for the circuitry. “Means shall be provided to
prevent inadvertent, and/or mistaken closure of the disconnecting device.”
EN 60204-1:1997.
• indicating lamp; ON = starting the drive is prevented, OFF = drive is operative.
For connections to the drive, see the circuit diagram delivered with the drive.
WARNING! The Prevention of unexpected start-up function does not disconnect the
voltage of the main and auxiliary circuits from the drive. Therefore maintenance work
on electrical parts of the drive or the motor can only be carried out after isolating the
drive system from the main supply.
Note: If a running drive is stopped by using the Prevention of unexpected start-up
function, the drive will cut off the motor supply voltage and the motor will coast to
stop.
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