8.17
Personnel safe restart lock -AS-
A frequently required application task is the protection of personnel against the restarting
of drives. This can be achieved by an electronic inhibit or with mechanical elements (posi-
tively driven relay contacts).
When positively driven relay contacts where used, either the net contactor in the mains
supply circuit switched off or the motor was disconnected from the servo amplifier by an
additional contactor.
The disadvantages of this method are :
— the DC bus link has to be charged up again at restart
— wear on the contacts of the contactors, caused by switching under load
— extensive wiring required, with additional switching components
The restart lock -AS- avoids these disadvantages.
The conceptual examination of the function "safe stop" (called restart lock AS in the fol-
lowing) was accomplished by the BG-Institute for Occupational Safety and Health and the
classification in category 3 according to EN 954-1 was confirmed.
Advantages of the restart lock -AS- :
—
the DC bus link remains charged up, since the mains supply line remains active
—
only low voltages are switched, so there is no contact wear
—
very little wiring is required
—
the functionality and the personnel safety when using the circuit recommendations
in this documentation have been approved by the Trade Liability Association.
8.17.1
Safety instructions
l
Observe the chapter "use as directed" for the restart lock -AS- (
ð
p. 78)
l
If the restart lock -AS- is automatically activated by a control system, then
make sure that the output of the control is monitored for possible malfunction.
This can be used to prevent a faulty output from activating the restart lock -AS-
unintendedly.
l
Since the restart lock is a single-channel system, erroneous engaging will not
be recognized.
l
Keep to the following functional sequence when the restart lock -AS- is used :
1. Brake the drive in a controlled manner (speed setpoint = 0V)
2. When speed = 0 rpm, disable the servo amplifier (enable = 0V)
3. If there is a suspended load, block the drive mechanically
4. Activate the restart lock -AS-
SERVOSTAR
®
300 Product Manual
77
Danaher Motion
10/2007
Electrical installation
