When a megohmmeter is used to test the...

Question 1 / 270705eccefa4bacbc34ba4d48407

Question 1 of 270705eccefa4bacbc34ba4d48407

When a megohmmeter is used to test the winding insulation of a large motor, what causes an initial dip of the pointer toward 'zero'?

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Question 1 of 27070

When a megohmmeter is used to test the winding insulation of a large motor, what causes an initial dip of the pointer toward 'zero'?

🔍 Key Concepts

• Megohmmeter (megger) operation when testing insulation resistance • How winding insulation behaves like a capacitor when voltage is first applied • Difference between steady insulation resistance and transient charging effects on the meter pointer

💭 Think About

• When you first apply DC test voltage from a megohmmeter to a large motor winding, what electrical effect happens before the reading settles? • Does a large coil of wire with insulation act only like a resistor, or does it also have another property that temporarily allows current flow? • Which choice describes something that would cause a brief, momentary current that quickly dies away, rather than a constant low-resistance reading?

✅ Before You Answer

• Recall that a megohmmeter applies DC voltage and measures resistance based on current flow • Think about how a coil of insulated wire can store charge between conductors and ground or between turns • Ask: Which option would cause a short-lived pointer deflection that quickly recovers, not a permanent low reading?

Question 1 of 27070

When a megohmmeter is used to test the winding insulation of a large motor, what causes an initial dip of the pointer toward 'zero'?

an open in the winding being tested

weak batteries in the meter

the absence of current along the surface of clean insulation

the capacitance of the winding

Question 1 / 270705eccefa4bacbc34ba4d48407

Question 1 of 270705eccefa4bacbc34ba4d48407

When a megohmmeter is used to test the winding insulation of a large motor, what causes an initial dip of the pointer toward 'zero'?

Back

Question 1 of 27070

When a megohmmeter is used to test the winding insulation of a large motor, what causes an initial dip of the pointer toward 'zero'?