State the permissible test result for an insulation resistance test for the electrical installation with ALL the permanently-connected electrical equipment DISCONNECTED - ANSWER1 Mega Ohm
State the permissible test result for an insulation resistance test for the electrical installation with ALL...
State the permissible test result for an insulation resistance test for the electrical installation with ALL
the permanently-connected electrical equipment DISCONNECTED - ANSWER1 Mega Ohm
State the permissible test result for an insulation resistance test for the electrical installation with ALL
the permanently-connected electrical equipment CONNECTED - ANSWER0.01 Mega Ohms
A three-phase induction motor normally runs on full-load. State ONE reason why this motor should
not be run LIGHTLY LOADED when it runs on full load. - ANSWER- The power factor of the motor will
be poor
- The motor will be less efficient
- running costs rise
A three-phase induction motor has been OPERATING NORMALLY ON FULL-LOAD. The motor starts to
over-heat even though it is drawing the normal full load current.
State ONE reason why this situation would occur - ANSWER- The motor ventilation is restricted in
some manner
- The cooling fan has become detached from the motor shaft
A clip-on ammeter is being used to test the integrity of the insulation of a repaired Class I electrical
appliance, while the appliance is live. Where on the appliance would the clip-on ammeter be used?
Also state the maximum test result that would allow the appliance to return to service. -
ANSWERClamped around the protective earthing conductor and 5mA
Explain what is meant by the term INVERSE TIME-CURRENT CHARACTERISTIC in relation to protective
devices - ANSWERas current through the protective device increases, the time taken to operate
decreases
State TWO components that are typically used to smooth the d.c output of a rectifier - ANSWER-
Capacitors
- Inductors
- Resistors
, The output circuit of an autotransformer MUST BE insulated for the highest input or output voltage
of the autotransformer. State ONE reason for this requirement - ANSWERAn auto transformer can fail
in such a way so the primary voltage appears across the secondary
An isolator for 230V electrical equipment has been replaced. During the work the phase (active) and
neutral were accidentally transposed at the supply side of the isolating switch.
What potential danger would this transposition create? - ANSWERThe internal circuitry of the
electrical equipment would be live when the isolating switch is in the OFF position.
What to the initials BJT mean when applied to semiconductors - ANSWERA bi-polar junction
transistor
State the function of a transducer - ANSWERA device that changes energy from one form to another
State TWO requirements for good illumination - ANSWERAny TWO of:
● Provides clear vision without eye strain
● Sufficient light intensity
● Minimum glare
● Uniform light intensity throughout the illuminated area
● Suitable colour rendering
XC - ANSWERCapacitive Reactance (ohms)
Explain why REWIREABLE FUSES are classed COARSE EXCESS CURRENT protection - ANSWERThere is
no certainty that the fuse will operate within 4 hours at 1.5x it's rated current
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