magnetic constant potential control].
2.4.2.3
Drive Control System
**************************************************************************
NOTE: Select dc micro-drive control for ac mainline
power control systems and dc micro-drive control for
dc mainline power control systems.
**************************************************************************
The [main hoist], [trolley] [and bridge] micro-drive control systems shall
be [ac] [dc] magnetic, single speed, reversing.
2.4.3
2.4.3.1
System Supply Voltage
Cranes shall be designed to be operated from a [_____] volt, [three-phase,
60 Hz, alternating current] [direct current] system power source. Energy
isolating devices for such machine or equipment shall be designed to accept
a lockout device in accordance with NFPA 70.
2.4.3.2
Transformers
**************************************************************************
NOTE: This paragraph is applicable to ac power
supplies only.
**************************************************************************
Transformers shall be dry type and shall carry full load continuously at
rated voltage and frequency without exceeding an average temperature rise
of 115 degrees C above an ambient temperature of 40 degrees C. The
transformer shall have a totally enclosed case which shall be finished with
manufacturer's standard coating system. Transformers shall be fully
encapsulated, except for those specifically designed for use as an
isolation transformer for static power conversion units.
2.4.3.3
Power Rectifiers
**************************************************************************
NOTE: This paragraph is applicable to dc power
supplies only.
Applicable rectifier requirements must be
coordinated for each specific job. Select totally
enclosed non-ventilated enclosure for indoor and
outdoor usage. Select totally enclosed fan cooled
enclosure for motors operating at rated speed for
long periods. Select forced ventilated air over
frame enclosure for motors operating at slow speed
for long periods or for severe-duty cycle service.
Select protective enclosure type. Enclosures
containing devices that produce excessive heat
(resistors) or ozone or devices that require cooling
for proper operation may require ventilation. Types
1, 2, 3R, 9 and 12 may be ventilated or
nonventilated. Type 1 enclosures are normally
specified for indoor cranes. Type 3R enclosures are
SECTION 14630A
Page 29
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