speed to full speed. Minimum hoist position of control shall not
allow hook to lower with 125 percent of full-rated design load on
hook, and the minimum lower position of control shall provide a
full-rated design-load lowering speed at not more than 2 percent
of rated speed. Control shall provide automatic regenerative or
dynamic braking for speed reduction and slow down before brake
setting.] [Emergency dynamic braking shall be provided when
control is in the OFF position and in case of power failure.]
[Control shall provide a 50-to-1 speed range.]
i.
[Hoist motor speed control shall provide ac adjustable
frequency-regulated, control of ac squirrel cage motors. Control
speed shall provide continuously-adjustable speed from minimum
speed to full speed. Minimum hoist position of the control shall
not allow hook to lower with 100 percent of full-rated design load
on hook, and the minimum lower position of control shall provide a
full-rated design-load lowering speed at not more than 3.3 percent
of rated speed. Control shall provide automatic regenerative or
dynamic braking for speed reduction and slow down before brake
setting.] [Emergency dynamic braking shall be provided when
control is in the OFF position and in case of power failure, or a
self-excited alternator shall be mounted on the electric load
brake housing to excite the load brake if power supply and holding
brakes fail.] [Control shall provide a minimum 30-to-1 speed
range.]
2.4.6.3
Bridge and Trolley Control
**************************************************************************
NOTE: Select a bridge and trolley control from
following paragraph a through f and coordinate with
paragraph Motor Enclosures.
**************************************************************************
a.
[Bridge and trolley main control systems shall provide [one] [two]
speeds in each direction with an electrically-operated,
full-magnetic, across-the-line reversing type starter.]
[Centrifugal switches shall be used in control circuit to prevent
the plugging of trolley or bridge drive motors; each switch shall
be arranged to set the associated drive's brake while attempts are
made to plug.] [The [bridge] [and] [trolley] main control system
shall be provided with reduced voltage starting for all speed
points.]
b.
Bridge and trolley main control systems shall be ac magnetic
control, five-speed, reversing, plugging type.
c.
Bridge and trolley main control systems shall be ac static
stepless secondary saturable reactor. Control shall provide
continuously-adjustable speed from minimum to full speed. Minimum
speed with zero hook load shall not exceed 15 percent of
full-rated speed. Control shall provide speed regulation of 15
percent or less from no-load to full-load at all speed settings.
d.
Bridge and trolley main control systems shall be dc magnetic
control type, five-speed, reversing, plugging type.
e.
Bridge and trolley main control systems shall employ dc stepless,
speed-regulated, adjustable-voltage control of dc shunt-wound
SECTION 14630A
Page 37
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