| General |
The EEx e motor
is not designed to withstand an internal explosion, but is
to an increased safety design.
Construction is similar to standard TEFV motors, but with
special attention to eliminate production of arcs, sparks
or dangerous surface temperatures. Air gap concentricity is
rigidly inspected throughout manufacture and the structure
of the motor is impact tested.
All motors comply with the requirements of the ATEX Directive
(94/9EC)
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| Temperature |
The important
feature of the motor design is the limitation imposed on internal
and external surface temperature that can be attained under
all conditions, including starting and under stall conditions.
Positive protection must be provided against the possibility
of dangerous overheating in the event of a locked rotor condition
(stall). When eternal temperatures will exceed the safe limiting
temperature, i.e. the T class, unless the motor is disconnected
within the te time.
The Te time is the time taken for ac windings, when carrying
the starting current IA to be heated up from the temperature
reached in rated service and at a maximum ambient temperature
to the limiting temperature. The Te time is never less than
5 seconds.
Appropriate control gear to disconnect the motor within the
Te time is essential
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In addition
to being non-sparking, the maximum temperature of all internal
and external surfaces must not exceed the specified T class
temperature, even under stalled conditions.
This range of motors is suitable for use in gases with auto
ignition temperatures not lower than T3, i.e. 200°C. For
temperature classes T4, T5 or T6 - please consult Brook Crompton.
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| Temperature rise
and outputs |
Standards specify
that reduced winding temperature rises apply to EEx e motors
according to the insulation system used. This is Class B 70°C
(by resistance). Frame outputs
Motors Can be supplied with increased outputs by using Class
F temperature rise (95°C). Details available on application. |
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