Safety Information
Introduction Mechanical Installation Electrical Installation
Digitax ST Installation Guide 7
Issue: 2 www.controltechniques.com
1.8.3 STOP function
The STOP function does not remove dangerous voltages from the drive, the motor or
any external option units.
1.8.4 Stored charge
The drive contains capacitors that remain charged to a potentially lethal voltage after the
AC supply has been disconnected. If the drive has been energised, the AC supply must
be isolated at least ten minutes before work may continue.
Normally, the capacitors are discharged by an internal resistor. Under certain, unusual
fault conditions, it is possible that the capacitors may fail to discharge, or be prevented
from being discharged by a voltage applied to the output terminals. If the drive has failed
in a manner that causes the display to go blank immediately, it is possible the capacitors
will not be discharged. In this case, consult Control Techniques or their authorised
distributor.
1.8.5 Equipment supplied by plug and socket
Special attention must be given if the drive is installed in equipment which is connected
to the AC supply by a plug and socket. The AC supply terminals of the drive are
connected to the internal capacitors through rectifier diodes which are not intended to
give safety isolation. If the plug terminals can be touched when the plug is disconnected
from the socket, a means of automatically isolating the plug from the drive must be used
(e.g. a latching relay).
1.8.6 Permanent magnet motors
Permanent magnet motors generate electrical power if they are rotated, even when the
supply to the drive is disconnected. If that happens then the drive will become energised
through its motor terminals.
If the motor load is capable of rotating the motor when the supply is disconnected, then
the motor must be isolated from the drive before gaining access to any live parts.
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