Control
Pendant - The pendant gives the operator precise control over the
motions of the crane. There are many configurations of pendant
depending on the functions of the equipment being controlled.
Each pushbutton on the pendent controls an operating function of
the crane.
The pendant may be suspended from the Trolley Hoist, requiring
the operator to walk with and beside the load, or on a separate
sliding track system allowing the operator to move independently
of the load.
VFD - A pendant can also be used in conjunction with a Variable
Frequency Drive. A VFD is used to vary the frequency of the
motors controlling the motions allowing for smooth acceleration
and deceleration. The buttons on the pendant operate a VFD unit
operated in much the same way as Two Speed control. The first
step is held to maintain the current speed while the second step is
used for acceleration. Deceleration is achieved by releasing the
button entirely. Pressing the button back to the first step will
maintain the new slower speed. It should be noted that the
deceleration is not achieved through uncontrolled coasting but
through a programable dynamic braking system. The control
provided by a VFD allows for a high level of customization.
Radio Control - The radio control performs exactly like the
pendant but operates using a radio frequency. The radio control
incorporates numerous safety features and allows the operator a
greater range of operator motion than a pendant.
Power Supply - The electrical service available in the building for
which the crane is being designed (i.e. 575 Volt, 3 phase, 60
Hertz).
Enclosures - The enclosures house all of the electrical
components on the crane and are rated by the National Electrical
Manufacturers Association (NEMA) or the Canadian Electrical
Manufacturers Association as to the level of protection they
provide from the conditions in the surrounding environment. There
are three basic levels of protection.
CEMA/NEMA 1 - Provides protection against accidental contact
with, and electrical shock from, enclosed equipment.
CEMA/NEMA 12 - Provides indoor protection against falling dirt,
dust, oil and water. CEMA/NEMA 4 - Provides indoor protection in hosed down, very
wet or outdoor environments, as well as falling dirt, dust, oil and
water. |
