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Lucien Nunes · 3rd May 2021, 12:09 am

Some random thoughts:

Keith Blackman made at least some of their motors in-house, not sure whether all. They were a large concern with multiple sites making all kinds of ventilation plant and ancillaries.

It's a totally-enclosed motor that might have been in the fan's airflow, in which case the capacitor (if required) might have been remotely located. That is about the only good reason for having three terminals. The resistance readings are indicative of a capacitor motor (or a 3-phase winding re-purposed as single-phase.) A traditional split-phase switch-start motor would typically have two windings of different resistance sharing a common terminal, hence giving three different resistance readings one of which is the sum of the other two. There is sufficient room for a centrifugal switch in the end bell, however the line current is low at 2A for a 1/3hp 240V motor, suggesting capacitor run.

Can you confirm the resistance (and if possible, inductance) readings and perhaps prove that they are a mesh of three similar coils?

On a different note, is that a Century RSIR motor I see in the background?

3rd May 2021, 12:09 am	#7
Lucien Nunes Rest in Peace Join Date: Apr 2008 Location: London, UK. Posts: 2,508	Re: Keith Blackman motor wiring Some random thoughts: Keith Blackman made at least some of their motors in-house, not sure whether all. They were a large concern with multiple sites making all kinds of ventilation plant and ancillaries. It's a totally-enclosed motor that might have been in the fan's airflow, in which case the capacitor (if required) might have been remotely located. That is about the only good reason for having three terminals. The resistance readings are indicative of a capacitor motor (or a 3-phase winding re-purposed as single-phase.) A traditional split-phase switch-start motor would typically have two windings of different resistance sharing a common terminal, hence giving three different resistance readings one of which is the sum of the other two. There is sufficient room for a centrifugal switch in the end bell, however the line current is low at 2A for a 1/3hp 240V motor, suggesting capacitor run. Can you confirm the resistance (and if possible, inductance) readings and perhaps prove that they are a mesh of three similar coils? On a different note, is that a Century RSIR motor I see in the background?