Supply Connection of 3 phase induction motor

Is it Ok to Connect Double Cable Motors to Supply in Manner as RR,YY,BB to l1,l2,l3 without Knowing Damp about Internal winding connection of motor?

Letters or numbers that are the same would normally go together. Your example is RR, YY, BB. They could be XX, YY, ZZ or 11, 22, 33. This is very often done on larger motors because two smaller cables are easier to handle than one large cable.

With the USA and Canada single speed motors: If you see a numbering system from1-6 it normally means that the motor is designed for a WYE-DELTA Start. If you see a numbering system from 1-9 this would indicate a dual voltage winding with the low voltage being 50% of the high voltage. This termed a 1WYE-2Wye connection or 1Delta-2 Delta. This would indicate a series connection for the high voltage and a parallel connection for the low voltage. The number of parallels can change but the low voltage will always have double the Parallels of the high voltage.

In Europe the main identification is lettering. U-V-W, X-Y-Z or U1, V1, W1 and U2, V2 W2 in the first example U and X are a phase, V and Y are a phase and W and Z are a phase. The phases are normally connected in series, (WYE), for the higher voltage, (possibly 380) and you can connect the phases in Parallel, (Delta) for a rated voltage of 58% of the higher voltage: (220-volts). This is also evident in the medium voltage motors that are rated 2300/4160. Wye Connected for 4160 and Delta connected for 2300. Don't you dare mix them up and connect for the wrong voltage.

If the motor lead cables are designated with the same symbol (letter OR number), they generally can be considered to be the same phase connection.

For larger equipment, the presence of six (or more) leads - each with different designations - can mean a lot of things. They can be for very different connection types: high/low voltage, multi-speed, multi-winding, wye/delta, or even phase/neutral. (Certain machines have the neutral leads brought out to connect to a common ground plane with the installation, rather than leave it "floating" within the machine. This is especially true of machines intended to operate on variable speed drives.)

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