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ELX > C4 LT3 > Flashcards

C4 LT3 Flashcards

1
Q

What is the purpose of using a Megohmeter?

A

Measure insulation resistance

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2
Q

What should be done to discharge the capacitive charge after testing?

A

Use discharge button or ground each conductor

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3
Q

What is the primary use of a megger?

A

To test the insulation of electrical equipment for resistance changes.

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4
Q

What should be done after testing the insulation of motor leads?

A

Test conductors feeding the motor

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5
Q

What does a major change in the insulation’s resistance value indicate?

A

That the electrical equipment could fail.

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6
Q

How should conductors feeding a motor be tested?

A

Disconnect from circuit

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7
Q

What hazard can be created when testing long runs of conductors in a conduit with a megger?

A

Potential shock hazard

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8
Q

How should the bare ends of conductors be protected against shock?

A

Electrical tape or insulated wire connector

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9
Q

What feature do most digital meggers have to prevent shock hazards?

A

Discharge feature

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10
Q

What should be done after turning on the megger and noting the readings?

A

Test each individual conductor to ground.

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11
Q

If a digital megger lacks a discharge feature, what is the recommended safety practice?

A

Ground the conductor before and after testing

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12
Q

What should be done after testing conductors to ground?

A

Test each individual conductor to other conductors in the cable or conduit.

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13
Q

How should you drain the capacitive charge on the conductor after completing the test?

A

Discharge using the megger or to system ground

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14
Q

What are Digital insulation testers commonly referred to as?

A

Meggers

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15
Q

List some causes of insulation deterioration.

A

Mechanical damage, fault currents, excessive heat, oil, moisture, voltage stresses.

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16
Q

What should you do before testing insulation with a megger?

A

Refer to manufacturer’s instructions

17
Q

Besides testing insulation resistance, what else are meggers used for?

A

Checking conductors for grounds, shorts, and opens.

18
Q

How should the megger voltage be set for insulation testing?

A

Not more than rated voltage of equipment

19
Q

What is the maximum voltage most ohmmeters can supply?

A

Up to about 9 volts

20
Q

What should be tested after the motor leads have been tested to ground?

A

Insulation between motor leads

21
Q

What should be checked before using a megger?

A

Maximum voltage rating of the conductor or component

22
Q

Where should one of the megger leads be connected?

A

To the ground of the electrical system

23
Q

What should always be referred to for testing procedures and features of the test equipment?

A

Manufacturer’s instructions

24
Q

Where should the other test lead be connected during testing?

A

To the bare end of the conductor under test

25
Q

What does a high megohm reading indicate on a megger test?

A

Good insulation and no short to ground.

26
Q

What should the reading be when testing between conductors?

A

A very high megohm reading.

27
Q

What does a megger provide to ensure the insulation will not break down?

A

High enough test voltage

28
Q

What should you do after draining the capacitive charge on the conductor?

A

Do Self-Test 3 and check answers

29
Q

What range of voltages can a megger supply?

A

250 volts DC to 5000 volts DC

30
Q

What caution should be followed when using a megger?

A

Never use on a live circuit

31
Q

What are the steps to test the conductors feeding a motor or equipment?

A

Connect one megger lead to frame, other lead to motor lead, push test button, read display, repeat for all leads, should be at least 1 megohm or higher

32
Q

What relationship exists between voltage rating and insulation resistance?

A

Directly proportional

ELX (55 decks)

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