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Other Vintage Household Electrical or Electromechanical Items For discussions about other vintage (over 25 years old) electrical and electromechanical household items. See the sticky thread for details. |
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2nd May 2021, 3:51 pm | #1 |
Octode
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Keith Blackman motor wiring
I've been helping my Dad with clearing out my Grandad's shed & garage over the last few weekends, we bought back a few motors yesterday including a Keith Blackman (seem to have made fan & blowers according to Graces guide) one.
Question is does anyone recognise the terminal letters so we can try it? The terminals are labelled S, R & M, there may or may not have been a fourth connection. David |
2nd May 2021, 4:20 pm | #2 |
Dekatron
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Re: Keith Blackman motor wiring
'S' and 'R' may be 'Start' and 'Run' refering to the ends of 2 windings to connect to a capacitor and/or centrifugal switch.
Have you tried measuring the resistance between the terminals? |
2nd May 2021, 8:00 pm | #3 |
Octode
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Re: Keith Blackman motor wiring
Taking off the test lead resistance I'm getting approx 6Ω between any combination of the terminals, there is nowhere to attach a capacitor that I can see and the terminal cover is threaded to go straight into conduit.
David |
2nd May 2021, 8:26 pm | #4 |
Tetrode
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Re: Keith Blackman motor wiring
I used Keith Blackman blowers and fans on gas fired web-offset print dryers in the 1970's. As the fans were a high centrifugal load, we ran the fan motors via a timer relay, with a change over between 'Start' and 'Run' at a specified time, dependent on the fan and HP of the motors....
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2nd May 2021, 10:00 pm | #5 |
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Re: Keith Blackman motor wiring
There doesn't seem to be a housing on that motor for a centrifugal switch, nor for connections from an internal one.
1400rpm says it's a 4-pole induction motor. S & R say it's for single phase. So it either has a capacitor start/capacitor run arrangement, or it has a timed start. There are no facilities for mounting a capacitor outside the connection box. With the windings hard-commoned there aren't facilities for reversing it, either. It looks to have been damp. The bearings might be doubtful. David
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3rd May 2021, 12:06 am | #6 |
Dekatron
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Re: Keith Blackman motor wiring
It looks like it might have had a contactor with two coils with a latching one on the (R)un terminal and a non latching coil on the (S)tart terminal.
You just push the start button and both windings are connected until you let the button go. It just blows the fuse if you hold the button for too long. Control gear was simple in old times. |
3rd May 2021, 12:09 am | #7 |
Rest in Peace
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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? |
3rd May 2021, 8:48 am | #8 | |
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Re: Keith Blackman motor wiring
Quote:
No capacitor that I know of. John.
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3rd May 2021, 9:04 am | #9 |
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Re: Keith Blackman motor wiring
Like the arrangement in John's post, in the 1960's this was a "Memota" made by Memrex, but these were three phase motors with connections with star for start and delta for run.
It's possible that David's single phase motor has a similar arrangement without a capacitor or centrifugal switch but just different start and run stator windings.
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3rd May 2021, 10:09 am | #10 |
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Re: Keith Blackman motor wiring
Although, if the resistances are 6Ω between any two terminals, that would be unusual for a split-phase switch-start, be it manual or centrifugal. The start winding usually has significantly higher resistance, and the readings would reveal the two windings sharing a common terminal by one reading being the sum of the other two. What the present readings suggest to me is that it is actually a delta winding, intended to run on a single-phase supply with a capacitor permanently in parallel with one coil. I am not sure why they would do that in this application but it will be interesting to further confirm the symmetry of the readings.
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3rd May 2021, 10:54 am | #11 | |
Dekatron
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Re: Keith Blackman motor wiring
Quote:
John.
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3rd May 2021, 11:23 am | #12 |
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Re: Keith Blackman motor wiring
Those readings seem both low and odd to me. I'd have expected M to be the common point of the two windings. Perhaps the motor has internal shorts?
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3rd May 2021, 2:50 pm | #13 | ||
Octode
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Re: Keith Blackman motor wiring
Thanks for all the replies.
It's possible it may have a short somewhere, some things my Grandad kept have proved to be knackered. Quote:
Quote:
And yes there is a Century repulsion start motor in the background, the spec plate is missing but it does have a plate for the sales agent "Swedish General Electric Ltd." which dates it to somewhere between 1915 & 1928 according to Graces Guide, it's also fairly rusty & caked in sawdust from being stored in the woodworking shed. David |
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3rd May 2021, 5:02 pm | #14 |
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Re: Keith Blackman motor wiring
I would be tempted to wire it up with a convector heater like a lamp limiter and with an insulated probe touch the start winding to the run winding.
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