Motor control Flashcards
relays
electromagnetic switches control a load
plug in relays
general purpose
wire terminal basee
control circuits
10 - 15 amps
induistrial control relays
heavy duty
switching control circuits
bridge contacts to reduce arcing that pits and weld
adder decks to increase contacts
power relays
direct switching of small motors and heating
not subjected to high cycle rates
30 amps
2hp
low voltage lighting relays
lighting systems
less than 30 V
single pole contacts
contactors
electromagnetic operated switches for high current
overload protection is seperate
NEMA
general purpose
simple
limited
IEC
design for life cycle
smaller size
reversing contactors
2 non reversing contactors with a mechanical and electromagnetic interlock
mechanically interlocked contactor
2 contactors with mechanical interlock
mechanically held contactors
latch in
large lighting
reduce power consumption
2 coils one energizes, one deenergizes
definite purpose contactor
HVAC
auto thermostat
FORM A
SPST NO
FORM B
SPST NC
FORM C
SPDT
FORM X
SPST NO DM
FORM Y
SPST NC DB
BIFURCATED CONTACTS
DOUBLE THE NUMBER OF CONTACT POINTS
PARALLEL PATHS
REDUCE CONTACT RESISTANCE
INCREASE RELAY SWITCHING RELIABILITY
SHADING COILS
CONTINUOUS LOOP OF COPPER EMBEDDED IN ARMATURE
SEALS IN ARMATURE
MINIMIZES CHATTERING
CONTACT MATERIALS
SILVER LOW VOLTAGE APPLICATION SELF CLEANING CAN BE WELDED
COPPER HIGH VOLTAGE HARD SURFACE HIGH PRESSURE PRONE TO OXIDATION
CADMIUM PLATED FREQUENT SWITCHING STRONG SPRING TENSION LONG LIFE NOT AS CONDUCTIVE
CONTACT SPRING
ABSORB SHOCK OF CLOSING
MAINTAIN PRESSURE
ARMATURE SPRING
PUSHES ARMATURE OPEN ON DEENERGIZATION
INCORRECT SPRING TENSION
INCREASE RESISTANCE
CONTACT BOUNCE
EXCESSIVE ARCING
SEAL IN VOLTAGE
85% RATED VOLTAGE
DROP OUT VOLTAGE
50% RATED VOLTAGE
COIL CURRENT BEFORE SEAL IN ARMATURE
4 -10 TIMES HIGHER
HIGH COIL VOLTAGE
VIOLENT SNAP IN
DAMAGE TO CONTACSTS
NEVER 110% MORE
LOW COIL VOLTAGE
CONTACTS DONT CHANGE
COIL BURN OUT
CHATTERING
ARCING
PITTING HIGHER RESISTANCE