The Secure Disable function in Unidrive  provides a highly
secure method for preventing the motor from being driven
when the enable signal is absent. It can be used in place of
one of the two output contactors normally used for this
purpose in an elevator drive, giving conformity to European
standard EN 81-1:1998 and providing savings in space, cost
and maintenance requirements.
This guide explains how to incorporate the drive into an
elevator control system, which is assumed to conform to
EN 81-1 with the use of two contactors, and to enable one
contactor to be eliminated.
The guide does not apply to Unidrive 6manufactured
before 2005. Anyone wishing to use this function please refer
to your local Drive Centre to confirm drive serial numbers
with EN 81-1 compliant control circuits.
Connecting the safety-related circuits
Figure 1 illustrates in general terms the existing system with a
drive without Secure Disable.
 Figure 1: Safety interface for existing controller with
two contactors
The controller output which previously operated contactor K1
now controls the drive enable input (Secure Disable).The
feedback for this channel is provided by a digital output from the
drive which is programmed to monitor the “enabled” parameter.
This interface can be through 24VDC logic levels or through an
interposing relay, as required by the controller design.
To program the digital output, refer to section 11 and menu 8
of the Unidrive User Guide.
 Figure 2: Safety interface for Unidrive with one contactor
Parameter 8.09 is the state of the enable input. Any of the
digital outputs or input/outputs can be programmed to reflect
8.09 by using their source pointers to point to 8.09.The
inversion function should be set so that the digital output is
high when the enable input is low.This gives the same sense as
the original auxiliary contact, and ensures that the more
common faults such as broken wires and earth faults in this circuit result in a fault indication to the controller.
If an interposing relay is used then it should have normally
open contacts, so that the more likely fault in the relay, nonoperation,
results in a fault indication to the controller.
Although not required for conformity with EN 81-1, if the
controller is of the programmable type then the correct
functioning of the “Monitor 1” drive digital output can be
monitored by checking that it goes low when the drive is
enabled, as well as going high when the drive is disabled. If it fails
to go low then the monitor circuit is not healthy and the
elevator operation should be prevented at the next opportunity.
Environmental protection
The drive must be protected from condensation and
electrically conductive contamination. In exterior elevator
control rooms subject to rapid temperature and humidity
cycles some form of anti-condensation heating must be used.
Independent verification to EN 81-1:1998
Provided that the controller with two contactors as shown in
Figure 1 was in conformity with EN 81-1 12.7.3 method a),
the system shown in Figure 2 will also conform to EN 81-1
12.7.3 method b).
The recommended arrangement, including this guidance note,
have been approved by TÜV as conforming to the
requirements of EN 81-1:1998 for interruption of the supply
to the motor.
The Secure Disable function has no failure modes which could
result in an unexpected output to the motor, other than
modes which are excluded in Annex H of EN 81-1:1998. In
this respect it is superior to the contactor, which has a
relatively high probability of sticking closed and relies upon the
auxiliary contact and second contactor to ensure safety in
this case.
The monitor circuit uses complex hardware and software.
Since it might fail in an undetected (high) state, it is
recommended that either automatic checking is used within
the controller, or else a manual check is carried out during
routine maintenance.The check should confirm that the
output goes low when the drive is enabled.
A failure of the monitor circuit does not cause the system to
become unsafe
ELECTROMAGNETIC COMPATIBILITY
Elevator requirements within the European Union are:
EN 12015:1998 Emission
EN 12016:1998 Immunity
The 1998 versions are current at the time of publication of
this guide (December 2004). Revised versions are expected to
be published early in 2005 (see below).
The emission limits in EN 12015:1998 are similar to
EN 61000-6-4, which is met by Unidrive when using
the recommended optional input filter and screened motor
cable. Full instructions are given in the Unidrive EMC
data sheet.
Particular notice must be taken of the recommendations
where a device such as the output contactor must be included
in the motor circuit.The EMC data sheet gives
recommendations for managing this situation, which must be
followed carefully.The output contactor and any associated
unscreened wiring, and the contactor coil wiring, must be kept
well spaced from the input wiring to the filter, otherwise stray
capacitive coupling will cause increased high-frequency
emission from the power input wiring.
Unidrive meets the requirements of EN 12016 unconditionally
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