mcsc

Question 1

when current flows through a conductor, the effects produced are

Answer 1

heat and magnesium

Question 2

over current conditions are caused by ?

Answer 2

short circuits or overloads

Question 3

2 types of overcurrnet conditions

Answer 3

short circuits, over load conditions

Question 4

3 sections of basic stop/start motor control circuits

Answer 4

stop circuit
start circuit
holding circuit

Question 5

what is the purpose holding contacts

Answer 5

to keep the coil energized when start button is released

Question 6

interlocks places in the stop circuit effects what

Answer 6

stopping of motor
running of motor
starting of motor

Question 7

what terminals of an IEC starter are used to control pilot light to indicate an overload relay was tripped

Answer 7

terminals 97, 98 Normaly open

Question 8

what is low voltage release

Answer 8

may automatically restart when the power come back on

Question 9

what is low voltage protection

Answer 9

will not automatically restart when power comes back on

Question 10

what is a common example of a low voltage protection circuit

Answer 10

a basic start/stop circuit with holding contacts that you need to restart after power is lost

Question 11

how many overload contacts in a reversing motor control circuit

Answer 11

one

Question 12

number of overload heaters required on a 3 phase reversing magnetic starter

Answer 12

3

Question 13

basic components of a reversing motor magnetic

Answer 13

2 contractors an one set of overload device

Question 14

purpose of mechanically interlocks on a reversing motor magnetic

Answer 14

to prevent both contactors from being pulled in or pushed in at same time/ prevents short circuit

Question 15

what is the main purpose of electrical interlocks on a reversing magnetic starter

Answer 15

prevent operating coil burn out
N.C

Question 16

IEC forward/reversing holding contact terminals

Answer 16

13, 14

Question 17

terminal numbers for NEMA forward/reversing holding contacts

Answer 17

2,3 forward 4,5 reversing

Question 18

define one-shot timing

Answer 18

contacts do not change state until the start terminals see a signal

Question 19

3 functions of multi functional timing relay

Answer 19

interval-timing, one-shot timing , repeat cycle-timing

Question 20

interlocks placed in the holding circuit effect

Answer 20

stopping only

Question 21

interlocks placed in the starting effect

Answer 21

starting only

Question 22

power light to indicate the circuit is energized

Answer 22

connected directly between L1 and L2 with no control device ahead of it

Question 23

some examples of low voltage release

Answer 23

sump pumps, air conditioners, hot water heating pumps, heating, ventilation.

Question 24

low voltage release should not use ?

Answer 24

overload devices that automatically reset. will casue burn out of motor

Question 25

examples of low voltage protection

Answer 25

lathes, band saws, escalators, industrial processes

Question 26

what would cause a 3 wire control ciruit to re energize after power loss

Answer 26

is the control devices are automatic pilot devices it may restart automatically

Question 27

if you can hear the armature or know that it pulls in when troubleshooting where is the problem most likely

Answer 27

in the power circuit

Question 28

when the armature is pushed in manually what reading would indicate burnt out overload heater

Answer 28

OL between L1 and T1

Question 29

to reverse a 3 phase motor

Answer 29

any 2 lines to the motor must be interchanged

Question 30

connection for forward pilot light

Answer 30

terminal 6 and L2

Question 31

connection for pilot light reversing

Answer 31

terminal 7 and L2

Question 32

electrical interlocks controlled by the forward coil are

Answer 32

terminal 5, 7

Question 33

electrical interlocks controlled by reversing coil are

Answer 33

3, 6

Question 34

electrical interlocks for IEC reversing and forward

Answer 34

21, 22

Question 35

3 methods of controlling the timing of a timing relay

Answer 35

Pneumatic, fluid dash point, electronically

Question 36

Define interval timing

Answer 36

Contacts will change instantly when relay coil is energized but will revert to normal state after a specific time

Question 37

Define repeat cycle timing

Answer 37

Provides regular on and off cycle for the timed contacts

Question 38

what features can smart relays have

Answer 38

modular memories, multiple input and output options

Question 39

programming of smart relays can be accomplished by

Answer 39

a pc or keypad function

Question 40

examples of electronically timing relays

Answer 40

plug in, rail-mounted, panel-mounted

Question 41

what is a non reversing contractor

Answer 41

is a single contractor what 3 main switching terminals

Question 42

define- mechanically held contractors

Answer 42

also called latching contractors, 2 operating coils

Question 43

definite purpose contacts

Answer 43

primarily used for heating, coolings , refrigeration, regulating or air moving applications

Question 44

how does laminations decrease eddy currents

Answer 44

they increase the resistance of the eddy’s current path

Question 45

what do contact springs do

Answer 45

minimize contact bounce

Question 46

what are armature springs used for

Answer 46

to force the armature open after the coil has been de energized

Question 47

how many contact points does a bifurcated contact have

Answer 47

4

Question 48

fault current is caused by

Answer 48

low impendence path to ground