Phase VW Short

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Excessive current has been detected between output terminals V and W, indicating a direct short circuit condition between motor phases V and W. This fault causes extremely high currents and will severely damage the drive's output transistors and the motor windings if not immediately resolved. Prompt investigation of wiring and motor integrity is crucial.

• Motor winding insulation breakdown between phases V and W, possibly due to prolonged thermal stress or localized hot spots within the motor.
• Motor cable insulation failure between conductors V and W, often resulting from tight bends, insufficient support, or vibration-induced wear.
• Conductive foreign material (e.g., metal filings, water droplets, oil) shorting terminals V and W within the motor or drive connection points.
• Wiring error at the motor connection, creating an accidental direct short between phase V and W at the motor terminal strip.
• Internal failure of the drive's output IGBTs for phases V or W, leading to an immediate short circuit within the power module.

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1. 1

   1. Disconnect all motor power cables from drive output terminals U, V, W.

2. 2

   2. Measure the resistance between motor terminals V and W with a digital ohmmeter (expected typical value for motor phase resistance: 0.5-20 Ohms).

3. 3

   3. Perform an insulation resistance test (Megger) between motor conductors V and W at 500VDC for 60 seconds (expected reading: >1 MOhm).

4. 4

   4. Visually inspect the motor terminal box for signs of carbon tracking, burn marks, or conductive debris bridging phases V and W.

5. 5

   5. Measure the resistance between the disconnected motor cable conductors V and W at the drive end with an ohmmeter to confirm cable integrity.

6. 6

   6. If motor and cable test good, measure resistance between drive output terminals V and W with an ohmmeter (drive powered off, DC bus discharged) to check for an internal drive short.