When a megohmmeter is used to test the...

When a megohmmeter is used to test the...

Question 1 of 270705eccefa4bacbc34ba4d48404

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

Question 1 of 27070

Q

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

🔍 Key Concepts

• Megohmmeter operation – what the meter actually measures when you first apply voltage to a large motor winding • Capacitance of motor windings – how a long length of conductor wound in coils behaves electrically • Insulation behavior over time – difference between a brief transient effect and true leakage or absorption

💭 Think About

• When you first connect and crank a megohmmeter on a large motor, is the current you see at that instant steady, or does it quickly change? What kind of electrical behavior causes a brief surge that then dies away? • Think of the motor windings like two plates separated by insulation. In that model, what happens the moment you apply a DC voltage across them? • Which of the choices would cause a continuous low-resistance reading, and which would only affect the meter for a short time at the start of the test?

✅ Before You Answer

• Identify which option would create a momentary charging current instead of a continuous leakage current. • Decide which effect is inherent in all large windings, even if the insulation is perfectly clean and dry. • Eliminate any choices that describe long-term or steady leakage problems, since the question asks about the initial dip toward zero.