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Identify Untagged 6-Leads out 3~ Motor

Part of being in Maintenance or Engineering Department in plant is the Corrective Actions where equipment or parameters are having issues or fault. To be an expert in solving problems or troubleshooting requires years of experience in plant.

One of the hardest parts of corrective maintenance is dealing with aged systems. “Abandoned” electrical panels, system with obsolete models, etc.

Untagged 6-phase motor could be one of them. In case of emergency that we need to use a motor with untagged leads, what would you do?

This article will show you how to identify untagged 6-leads out, 3-phase motor. This is one of the topics that I thought to my class when I worked as a part-time teacher. Before you do the steps, make sure you have the complete materials and tools such as multimeter (preferably analog), 9V battery, marker and insulation tape. Below are the steps in identifying 6-leads out untagged 3-phase motor.

Step 1. Use continuity test method to find 3 sets of windings.

Step 2. Select reference winding from 3 windings either A, B or C.

Step 3. Set polarity mark in your selected reference winding.

Step 4. Use inductive kick test to check the polarity mark of the other winding considering the reference winding as your primary and other winding as your secondary.

  • Connect the reference winding to a DC source. 9VDC Battery can be used as DC source
  • Check the kick voltage of winding B and monitor the deflection
  • Check the kick voltage of winding C and monitor the deflection

Step 5. Use three leads-out method to identify T1, T2 and T3 by connecting three windings in WYE or STAR connection. Motor must run in clockwise direction. Interchange any of two lines and check if motor will run in counterclockwise.

Therefore, L1 connected to T1, L2 connected to T2, and L3 connected to T3. The end terminal of T1, T2, and T3 are T4, T5, and T6 respectively.

Note: A lot of people having misconception on this problem that they thought it can be done by just continuity test for each pair terminals. However, polarity must be considered too so that all phase are in the same direction whether you run the motor in forward or reverse.

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