UNDERSTANDING LATCHING
SOLENOID TECHNOLOGY
WHAT IS A LATCHING SOLENOID?
 A latching solenoid utilizes the
electrical current pulse or internal
permanent magnet material to
maintain a set position without the
constant application of power.
 A bistable solenoid is another name
often used for latching solenoids
because they typically have two stable
positions.
Position #1: Solenoid is de-energized and
plunger is fully extended
Position #2: Solenoid is de-energized and
plunger is held in position by permanent
magnets
HOW DOES A LATCHING SOLENOID OPERATE?
• Electrical polarity is important to obtain proper operation in
a latching solenoid.
• As current flows in one direction energizing the coil field, it
adds to the pull of the permanent magnet making the
armature attracted to the stationary pole.
• Once the armature has moved full travel and is in contact
with the pole, it will remain in a latched position without
further electrical input. The armature is held in position by
the permanent magnet.
• To release from the latched position, the magnet’s
attraction is cancelled by sending a current through the coil
field in the opposite direction.
TYPES OF LATCHING SOLENOIDS
Permanent Magnet—Latching solenoids
that utilize permanent magnets in
conjunction with the solenoid coil to
maintain the position of the armature when
no current is applied.
When a short pulse of electrical current is
applied to the coil, a small magnetic flux is
added to the permanent magnet and moves
the plunger to the fixed pole piece.
When the current is removed, the
permanent magnet will hold the armature in
the latched position.
Applying a reverse polarity pulse will cancel
the flux of the permanent magnet allowing
the load or spring to release the plunger
and move to the de-latched position.
TYPES OF LATCHING SOLENOIDS
Residual Magnetism—Much like latching
solenoids that utilize permanent magnets,
latching solenoids maintain the position of
the armature when no current is applied.
The solenoid uses internal design features
to enhance the residual magnetism inherent
to all DC solenoids. When current is
applied, the solenoid will latch into position
and hold utilizing the residual magnetism
properties of the coil.
The solenoid will remain in the latched
position until a current of reverse polarity is
applied. Once unlatched, the solenoid will
not re-latch until power has been applied
again.
BENEFITS OF LATCHING SOLENOIDS
Latching solenoids can be turned off
for most of the “on” cycle allowing the
use of a higher current pulse which
produces faster speed operation and
generates a higher pull force without
the excessive power consumption or
heat generation of a conventional
solenoid.
While holding in either the on or off
position, latching solenoids utilize
almost no power, produce no heat and
generate no electrical noise compared
to conventional solenoids.
Due to their low power consumption,
latching solenoids are well suited for
battery operated applications.