Strange Motor Wiring: 6 Motors, 200HP, 380V 50Hz

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Discussion Overview

The discussion revolves around the wiring configuration of six 200 HP, 380V, 50Hz motors. Participants are examining the continuity test results that show terminals 1, 2, 3 are connected together and terminals 7, 8, 9 are also connected together, raising questions about the expected wiring setup and potential issues with the motors.

Discussion Character

  • Technical explanation
  • Debate/contested

Main Points Raised

  • One participant notes that the motors are labeled with terminals 1, 2, 3, 7, 8, and 9, and questions how the connections are possible given the continuity test results.
  • Another participant proposes that the motors are likely 1250 RPM, 3-phase motors.
  • A different participant suggests the motors could be 1485 RPM, 3-phase motors.
  • One participant speculates that the motors might be wound rotor induction motors and inquires about the presence of slip rings and brushes.
  • A participant asks for the resistance measured during the continuity test and suggests performing a resistivity test, noting that some multimeters may show misleading high resistance values.
  • One participant acknowledges a mistake in calculating the synchronous RPM and explains that a low RPM motor would have additional poles and wires compared to a high RPM motor.
  • Another participant reports measuring around 0.5 ohm between any two connected terminals (1, 2, 3 or 7, 8, 9) and expresses concern about the possibility of a fault in all six motors, given their age.
  • One participant asserts that the sets of three terminals are likely connected in a delta configuration, which would explain the low resistance measurements observed.

Areas of Agreement / Disagreement

Participants express differing views on the motors' RPM ratings and potential wiring configurations. There is no consensus on whether the observed connections are correct or indicative of a fault.

Contextual Notes

Participants have not fully resolved the implications of the continuity test results, and there are uncertainties regarding the motors' specifications and wiring configurations.

esso
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hey guys... i have 6 motors at work, 380V, 50Hz, 200 HP. the terminals are labeled 1,2,3,7,8 and 9.
continuity test showed that 1,2,3 are connected together, and 7,8,9 are connected together. how is that possible ?? am i missing something ?? note that that is the case in all 6 motors.
thx
 
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I am assuming this is a 1250 RPM 3 phase motor?
 
1485 RPM , 3 phase motor
 
Wound rotor induction motor is somthing that comes to my mind.

Does it have slip rings and brushes?
 
How many ohms in continuity test? I would suggest doing resistivity test. Some multimeters show ohms as high as 25 as continious.
 
My bad, I should have taken 50 x 60 / 2 to get the synchronous RPM. Instead I took 50 x 50 / 2. If this were a high RPM motor (2970) you would only have 3 wires. Since it is a low RPM motor you have an extra set of poles and wires.
 
around 0.5 ohm between any two connected terminals (1,2,3) or (7,8,9).
Having the extra set of poles and wires doesn't explain why are they connected.
i'm beginning to think that there's something wrong with them (they're made in the eighties after all) , but what's the odds that all 6 of them have the same problem.
 
So just how do you think they should be connected? I am pretty sure that the sets of 3 are connected in a delta fashion. You would naturally measure a low resistance between them as you have.
 

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