More On Single-Phase For Three-Phase Monarchs
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# Thread: More On Single-Phase For Three-Phase Monarchs

1. ## More On Single-Phase For Three-Phase Monarchs

Herein I will explain how it is possible for a three-phase Monarch (most models, anyway) to be converted to single-phase.

The basis of this conversion is the Henry A. Steelman (hence, "HAS") capacitor-start/capacitor-run method, in which the load motor is operated as a two-phase motor, with 90 degrees difference between one winding and the "resultant" of the other two windings (see the earlier thread for references, including how to convert a nine-wire motor to the required twelve-wire configuration).

Referring to the first thumbnail, and starting with the lower left-hand schematic diagram within that thumbnail (and moving in a clockwise direction) ...

1) A twelve-wire motor winding schematic,

2) the connections of this motor for a three-phase 240 volt source,

3) the connections of this motor for a three-phase 480 volt source,

4) the connections of this motor for a single-phase 240 volt source (two-phase "HAS"),

5) the connections of this motor for a single-phase 480 volt source (two-phase "HAS"),

6) the forces within such a two-phase motor when running in reverse, and

7) the forces within such a two-phase motor when running in forward.

Referring to the second thumbnail, the actual internal connections for 240 volts (left) and 480 volts (right) are shown.

The external terminal designations T1, ..., T4 are consistent with the usual connections for two-phase motors. As usual, reversing is accomplished by exchanging T1 and T2, while T3 and T4 remain as before.

Of special note is the connection to the sensing coil of the starting means. For 240 volts, the potential across the entire "quadrature" winding is sensed, whereas for 480 volts, the potential across one-half of the "quadrature" winding is sensed. This presents the same voltage to the potential relay, regardless of the 240 volt or 480 volt source.

Referring to the third thumbnail, the schematic diagram of the AC section of a converted 10EE is shown.

Because the 10EE has a Size 0 starter, the main winding is split across two starter contact sets.

T1-1 (#1 of the motor) is brought to the terminal which is directly opposite L1 of the starter (this is a strap to the overload immediately below it, which is removed by this method). T1-2 (#7 of the motor) is brought to the T3 terminal of the contactor. The sum of the currents in T1-1 and T1-2 is found at T2 (#2 and #8 of the motor), and this brought to T2 of the contactor, one of the two overloads. It is not necessary, nor is it possible to split this winding in a 480 volt application of this method on this machine. The unlabeled terminal of this overload is returned to L2.

Continuing with this thumbnail, the terminal which is opposite L2 of the contactor (this is also a strap, which is also removed by this method) is routed to S1 of the starting means, which will be explained later. The return from the starting means, S2, is connected to the unnamed terminal of second overload. T3 (#3 of the motor) is connected to the T1 terminal of the second overload. PR1, which is another conductor, is connected to the starting means, as is PR2, also another conductor. Finally, T4 (#12 of the motor) is returned to L1.

The "three-wire control station" operates exactly as it did before the conversion.

The starting means, which optionally includes power factor correcting capacitors, Cpf, contains a starting circuit, a sense circuit and a running circuit. The starting contactor actuator (this is a Steveco 90-66 potential relay in the preferred implementation) activates the starting contactor. Terminal 2 of the potential relay is returned to L1. The starting contactor (this is a "definite purpose" contactor with three or four poles rated 30 to 50 amps each in the preferred implementation) initially connects the starting capacitors, Cs, to the phase-shifting capacitor, Cr, under the control of the potential relay. The phase-shifting capacitor, in intermittent combination with the starting capacitor(s), imposes a 90 degree phase shift between the main windings and the "quadrature" winding. The several starting capacitors are distributed across the poles of the starting contactor.

When the START push button is depressed, the line voltage is applied to the main windings, T1 (comprising T1-1 and T1-2) and T2. Also, the line voltage, shifted +90 degrees by Cr, and augmented by Cs, is applied to the "quadrature" winding, T3 and T4.

Initially, the potential across T3 and T4 is very much below the sensing voltage of the potential relay. As the M-G accelerates towards synchronous speed, the sensing voltage begins to increase. After the M-G has fully accelerated, the sensing voltage is enough to cause the potential relay to open, which also drops-out the starting capacitors.

Finally, the M-G is now running as a two-phase induction motor, with full rated HP.

When the STOP push button is depressed, or either of the overloads or interlocks are activated, power is removed from the M-G, and the machine comes to a halt.

Because of the design of this device, full rated power is available at all times from the M-G, therefore full rated HP is available at the spindle of the machine.

I will later revise and extend this concept for application to the various Monarchs which utilize a reversing magnetic motor starter (the "Series" machines, for example).
Last edited by peterh5322; 04-26-2010 at 07:58 PM.

2. Hot Rolled
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Whoa- I'm going to have to read that about 12 times to sort that all out, but that sounds pretty awesome!

3. Hi Peter....

Yeah, what he said.....I'm in the audience, too, squinting from the front row.....

Thanks for that....Chris

4. Supplementary note ...

There was an error which crept into the schematic diagram of the 10EE conversion (the third diagram).

The left-hand overload should be labeled OL1 as its output terminal is labeled T1.

The right-hand overload should be labeled OL2 as its output terminal is labeled T2.

Explanation of contactor terminal labeling ...

In the original Cutler-Hammer Size 0 magnetic motor starter, the terminals on the upper row (line side) are labeled, right to left, 3, L2, L1 and L3, and the corresponding terminals on the lower row (load side) are labeled, right to left, 1, T2, T1 and T3. (3 and 1 are, of course, utilized in the "three-wire control station").

The contact sets which are labeled, right to left, L2 and L1 on the line side are connected to the overloads by straps on the load side, and it is the outputs of these overloads which are labeled, right to left, T2 and T1.

By removing the two straps, access is gained to the overloads themselves, so that these overloads may be re-purposed for this single-phase application, where one overload protects the main windings, and the other overload protects the "quadrature" winding.

The way the overloads are employed in this application, the sum of the currents in the two main windings goes through the overload labeled T2, which is OL2, and the current in the "quadrature" winding goes through the overload labeled T1, which is OL1.
Last edited by peterh5322; 04-27-2010 at 12:28 PM.

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Peter, thank you for posting this, I'm mulling over making this conversion. Not the least of its advantages are lower cost and increased overall efficiency by eliminating phase conversion hardware (RPC or electronic) yet still developing full HP.

I didn't look for the triple point connection in the motor field when I had my MG apart. Has anyone located it and made the conversion to twelve-wire motor?

6. "I didn't look for the triple point connection in the motor field when I had my MG apart. Has anyone located it and made the conversion to twelve-wire motor?"

The Henry A. Steelman patent gives the theory of the application. The Steelman Electric Service instructions give the details of the application.

Another poster has executed these instructions, or his interpretation of the same, and has confirmed the performance results using a "prony" brake system, which verifies the "brake horsepower" of the converted electrical machine.

7. "I didn't look for the triple point connection in the motor field when I had my MG apart."

In a nine-wire motor, the "star point", which would be the confluence of T10, T11 and T12, should be found at a brazed joint which is insulated and then laced to the windings before the entire assembly has been vacuum-impregnated with insulating varnish.

Separating this point and then applying and brazing three additional leads, to be labeled T10, T11, and T12, is one operation.

Checking the continuity of T10 to T7, T11 to T8 and T12 to T9 is another operation.

Routing T10, T11 and T12 out through the connection box (the "peckerhead") is the final operation.

I have performed these operations on other three-phase motors, but not specifically on the Reliance M-G unit .

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