Hubbell Industrial Controls, Inc.
EUCLID™ AC & DC POWER LIMIT SWITCHES
SIZE 2, 3, 4, 5, 6, & 6A
SPECIFICATIONS
4220
November 2010
Repl. June 1994
General Information
D-C Limit Switches
are devices
that are used to interrupt the main
power circuit, setting up a dynamic
braking circuit that quickly stops
hook travel with a minimum of drift.
A-C Limit Switches
are similar in
construction to D-C Limit Switches.
The difference is in operation. A-C
Limit Switches disconnect two
power lines to the hoist motor
which then is stopped by a mag-
netic brake.
♦
Positive trigger lock-out
♦
Direct action contact open-
ing and closing
♦
One-piece movable contacts
♦
Exclusive arc transfer action
♦
Sturdy housing
♦
Safety chain on cover
♦
Clearly marked leads
♦
Rugged construction
♦
Oversize ball bearings
Application
Euclid A-C and D-C Crane Power
Limit Switches provide dependable
protection against over-hoisting
problems such as damage to the
trolley frame and hoising mecha-
nism. In case of over-travel, these
Limit Switches disconnect the hoist
motor from the line, preventing
further hoist motion.
Operation
For dc operation
the Power Limit
Switch is mounted on the trolley
floor of the crane. When the hook
block rises into the danger zone, it
lifts the suspended reset weight.
As the load of the reset weight is
removed from the operating lever,
the tripping weight (an integral part
of the operating lever) operates the
switch. Normally closed power
contacts are opened, normally
open dynamic braking contacts are
closed through a resistor. The
motor armature and series brake
are disconnected from the supply
line. The armature, series field and
braking resistor are connected in
series. RESULT: Setting of the
series holding brake and dynamic
breaking for a quick stop.
Reversing the crane controller low-
ers the hook to return the Limit
Switch to the “run” position by
means of the suspended reset
weight.
For ac operation,
when the Power
Limit Switch is tripped, the shoe
brake is applied and the load is
stopped. The load cannot be
Hoisted when the Limit Switch is
tripped, but Lowering can be per-
formed as usual because the low-
ering circuit is unaltered.
