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I have an Electro ADDA C80M-2 0.75kW single-phase blower motor that I need to hook up, switched, to power a cyclonic dust separator that I've built. I thought it would be a piece of cake: pop off the wiring cover and red-to-red, blue-to-blue, green to earth. But this is what I found:

Photo of motor wiring enclosure Wiring schematic from enclosure lid

The dark world of electric motor schematics with Z2, U1, Cr (switch?) et cetera. Bit much to expect line and neutral marked, I suppose?

If I'm reading the schematic correctly, it's currently set up to rotate in the clockwise direction and I've attached the earth terminal, thanks to the nice symbol on the casing, but I'm afraid I don't have confidence in which terminal to take live and neutral to.

Please help if you can.

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  • \$\begingroup\$ As I read the label, it doesn't matter which is line and which is neutral. Presumably, it is designed neither needs to be neutral for safety; the ground terminal provides all of the necessary protection. \$\endgroup\$ – DoxyLover Oct 8 '14 at 3:58
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Pictures should help:

enter image description here

As @Asmyldof stated, the motor has no concept of hot or neutral, so the polarity of the AC connections is not important. Connect one of them to hot, and one of them to neutral. The motor will turn the same direction even if you reverse these connections. To reverse the motor, you have to remove the metal jumpers, and reposition them as indicated by the diagram.

Note that you absolutely should ground the motor housing, but this is a protective measure (the yellow/green-stripe wire is the earth/ground connection), but ground is not neutral.

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With Alternating Current (single phase) it doesn't matter to the electronics/electrics which goes where, because the current flows in both directions in equal amounts over equal time periods, so the device can't see which is which.

Unless it compares them to Earth, which it shouldn't do, because that means putting a current into earth and possibly tripping earth-fault protectors (if not humans licking the fan, we all do it once in a while).

If there's a neutral indicated, it's a suggestion for safety, because some part of the wiring comes closer to a casing than another part, or it's just arbitrary engineer's choice. No indication? No matter! Especially since you also have an Earth connection.

Now, Cr is not a switch. Cr is an essential component, which hopefully is still attached to that pretty yellow and blue cable. It's a capacitor that allows the motor to start and run smoothly as it was designed to. If you don't have it any more, some calculations can be done to get in the ballpark of a decent value, followed by trying the one in the middle of that and seeing what happens. But, as you can imagine, still having the original is quite a lot easier.

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  • \$\begingroup\$ I see. So do I connect across the capacitor (V1-Live, Z1-Neutral) or across the jumper bars at the top of the photo? The squiggly line seems to represent AC, suggesting the latter. Is that a reasonable conclusion? \$\endgroup\$ – Wobblefoot Oct 8 '14 at 23:47
  • \$\begingroup\$ The squiggly line does mean the Live and Neutral connection. The physical set-up reflects the M-connection, as you guessed, so to see "what happens" with CW rotation, connect the live and neutral as the two connections going up along the ~ in the M connection drawing. So basically most (all if you exclude switch/cap) gut-feelings are right in this case :-) -- Still: Always be careful and ready to pull the plug or switch off right away... \$\endgroup\$ – Asmyldof Oct 9 '14 at 0:41

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