PRINCIPLE OF OPERATION
The sectional view shows our normally open style
Mercury Displacement tube with the plunger assembly
floating on the mercury pool.
When the coil power is off, the mercury level is below
the electrode tip. No electrical path exists between
the electrode and mercury pool.
When coil power is applied, the plunger is drawn down
into the mercury by the pull of the magnetic field.
This action raises the mercury level, so it covers the
end of the electrode closing the circuit.
When coil power is turned off, the buoyant force of
the mercury causes the plunger assemble to rise,
dropping the mercury level, and breaking the circuit.
APPLICATION DATA
Mercury Displacement relays are ideal for adverse
environments-
....Where high inrushes are encountered
....Where hermetically sealed contact operation is
required because of corrosive, dirty, or moist
ambient conditions.
....Where use does not permit contact maintenance.
....Where reduced noise levels are required.
....Where minimum weight and size are desired.
DESIGN FEATURES
Mercury Displacement Relays provide a perpetually self-
renewing contact to assure maximum contact life and
minimum contact resistance. Conventional contactors
are destroyed by pitting and welding under high load
conditions. MDRs have a single moving part that floats
free on a pool of mercury. There are no hinges, pivots,
pins or mechanical linkage to wear out or break. The result
is a life expectancy which exceeds other types of contactors
handling the same loads and duty cycle.
Liquid Mercury Contact - provides a new contact surface
with every actuation. Mercury is self-renewing and does
not pit, weld, disintegrate or oxidize.
Hermetic sealing - provides internal and external protection
from arcing.
Inert Gas atmosphere - contactor tube is evacuated, then
pressurized with a combination of gases which extinguish
arcing and contribute to long life. The pressurized gases
provide for a high dielectric withstanding voltage between
contact surfaces.
Low Contact Resistance - Large electrode and mercury
volume creates low contact resistance and provides high
inrush current capability.
Quiet Operation - Audible noise normally associated with
conventional contactors is eliminated with mercury
displacement tubes and the buffer spring assembly.
APPLICATION OF "M" SERIES VS "ML" SERIES
The series "ML" is physically the same as the "M" series
except for the type of gases used in the contactor tubes.
The "ML" series was developed for use with resistive and
tungsten loads on AC power ONLY. The "ML" series will
give much greater life than the "M" series for these types
of loads and is intended for high activation use, such as
molding machines or ovens. The "ML" series, however is
not intended for use with motor loads on AC power, or for
resistive, tungsten, or motor loads on DC power. The "M"
series, which is our universal series is rated to be used
on all types of loads resistive, tungsten, and motor for
both AC and DC power.
RECOMMENDED FUSE PROTECTION
MDRs are capable of accepting high inrush currents
however, short circuit currents can damage the contactor.
Fast acting fuses should be used in-line with the contactor
load to protect against short circuit fault current. UL class
J and class RK-1 fuses are recommended.
GLASS INSULATOR
WELD
PLUNGER GUIDE
CERAMIC LINER
ELECTRODE
ARC QUENCHING ATMOSPHERE
MAGNETIC LINER
PLUNGER GUIDE
BUFFER SPRING
MERCURY POOL
STAINLESS STEEL CAN
MERCURY DISPLACEMENT TUBE
MDR
MERCURY DISPLACEMENT RELAYS
APPLICA
APPLICATION D
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