Consequent-pole Two-speed Motor Controls - Was: (Something Else)


Interesting. I've never personally seen a two-speed motor like that, only the kind that hardinge have, where the controller switches the configuration from star to delta to pole change.

I have posted an exhaustive description of a Hardinge consequent-pole two-speed motor control, as found in the later model TL (Toolroom Lathe, AKA, T-10), on the Hardinge-Lathe Yahoo! group:
http://groups.yahoo.com/group/Hardinge-Lathe/message/272
Lower initial cost, and a smaller frame size are reasons for specifying this type of motor, over an otherwise equivalent two-winding motor.
These motors are usually constant-torque, and are configured as four-pole, parallel-star (2Y) and eight-pole, series-delta, using one winding.
Peter.
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Unfortunately not visible to me. Possible to post in dropbox?

Sounds like the person at the top was talking about the same kind of motor - the motors I'm used to seeing in hardinge machineare are four or eight pole, switched from star to delta to obtain the speed change. Not with just one winding though.
Are the consequent pole motors truly different?
Jim
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<A HREF="http://groups.yahoo.com/group/Hardinge-Lathe/message/272 ">http://gro ups.yahoo.com/group/Hardinge-Lathe/message/272</A>
Unfortunately not visible to me. Possible to post in dropbox?

I will try.
In the mean time, see below.
[ snip ]

Sounds like the person at the top was talking about the same kind of motor - the motors I'm used to seeing in hardinge machineare are four or eight pole, switched from star to delta to obtain the speed change. Not with just one winding though.
Are the consequent pole motors truly different?

These are either constant-torque (the most common, and the type used by Hardinge), variable-torque, or constant horsepower (rarely seen).
There is only one winding, but it is distributed across eight poles and three phases.
Since there is only one winding, the required slot size, and, consequently, the required frame size, is reduced.
Re: TL (T-10) Late Model Starter
From: http://groups.yahoo.com/group/Hardinge-Lathe/message/272
Revised 2/20/2004 (Paragraphs prefixed by "| ").
Hardinge released a magnetic-type starter for the TL (T-10) in about March 1947, replacing the manual-type starter found on earlier machines.
(March 1947 isn't necessarily the precise date for its introduction, however, this date, "3/47", is printed on the bottom of the diagram posted by Jim in his "Jim's T-10" photo section).
Normally, for a "consequent-pole" motor, one five-pole and one three-pole magnetic starters are required. Hardinge implemented this starter with one three-pole magnetic starter, and a drum switch of unusual configuration.
Now, that is for the high/low speed function alone; the forward/reverse function is also implemented using a drum switch, although its configuration is conventional.
Referring to the schematic posted by Jim ...
Hardinge drew this schematic diagram in an unconventional way, breaking the high/low drum switch into four sections of two apparent poles each, and the forward/reverse drum switch into three sections, with two apparent poles in the first two sections and one pole in the last section.
However, there are really only five poles in the high/low switch and three poles in the forward/reverse switch, which is consistent with most manual-type consequent-pole starters which provide for reversing.
In order to better describe the March 1947 Hardinge control, I will re-label the sections and poles of the high/low switch as follows, from top to bottom:
1) Sections 1a and 1b: wires 3, T5 and T3; fast and slow, respectively,
2) Section 2: fast only,
3) Section 3: fast only,
4) Sections 4a and 4b: wires 1, T1 and T6; slow and fast, respectively,
5) Sections 5a and 5b: wires 2, T2 and T4; slow and fast, respectively.
(Wires 1, 2, and 3 come from the reversing switch, and represent the three phases, but not necessarily Phases A, B and C, as will be described later).
In the center, or off position, no connections are made.
In the fast position, wire 3 is connected to T5 by section 1a, using a terminal of section 1b; wire 1 is connected to T6 by section 4b; and wire 2 is connected to T4 by section 5b, additionally, T1, T2 and T3 are connected together by sections 2 and 3.
In the slow position, wire 3 is connected to T3 by section 1b, using a terminal of section 2; wire 1 is connected to T1 by section 4a, using a terminal of section 4b; and wire 2 is connected to T2 by section 5a, using a terminal of section 5b.
| The above described connections accomplishes the switching of the classical four-pole consequent-pole, constant-torque, two-speed motor. The motor is operated in four-pole parallel-star (2Y) mode for high speed, and in eight-pole series-delta mode for low speed.
The reversing drum switch is perhaps a little easier to understand.
I will re-label the sections and poles of the reversing switch as follows:
| 1) Sections 1a and 1b: wire L1; forward and reverse, respectively,
2) Sections 2a and 2b: wire L3; forward and reverse, respectively, and
3) Section 3: wire L2; forward or reverse.
| In the center, or off position, no connections are made.
In the forward position, wire L1 is connected to wire 1 by section 1a, using a terminal of section 1b and a terminal of section 2b; wire L3 is connected to wire 3 by section 2a, using a terminal of section 2b; and wire L2 is connected to wire 2 by section 3.
In the reverse position, wire L1 is connected to wire 3 by section 1b, using a terminal of section 2a; wire L3 is connected to wire 1 by section 2b; and wire L2 is connected to wire 2 by section 3.
The above described connections accomplishes the reversing of the generalized three-phase motor.
(Wires L1, L2 and L3 represent phases A, B and C, respectively; wires 1, 2 and 3 represent these phases, after reversing, if any, has been applied. Phase B/L2 are not reversed).
Hardinge's March 1947 design incorporates a standard NEMA Type 0 magnetic starter, for both low-voltage control (high-voltage control is an option) and for motor running protection, avoiding the complications of a purpose-built consequent-pole-type magnetic starter, while retaining the extant manual consequent-pole and reversing drum switches, which were apparently adapted from an earlier version of the TL.
This innovative control design has the obvious advantages of a magnetic starter, and low-voltage control (unless high-voltage control was specified), at significantly lower cost. However, the schematic diagram is somewhat counterintuitive.
Many thank to Jim [ Jim S. ] for posting the March 1947 schematic diagram.
Peter.
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In some of their machines (for example the older milling machines) they simply use two drum switches. The first is a common forward/off/reverse drum switch that is wired in the conventional way, with center off and one pair of lines is interchanged in one of the on positions, to reverse the motor.
The other drum switch does indeed have more poles, but it is a bit more complicated in it's operation. The rotor in the switch is special purpose to run a pole changing motor. Here again center is off and no contacts ring through. Its purpose is to correctly connect the three incoming power lines to the six (for a single voltage motor) motor leads.
Consider the motor windings to be set up in star configuration, with the center of the star all common. However each winding has a center tap midway along its length. This gives a total of six wires emerging from the motor, three 'ends' and three 'centertaps.'
In low speed the center taps are not connected to anything, and the ends of the star windings are connected to the incoming lines as in any regular three phase motor.
However in high speed the incoming lines are connected instead to the centertap wires, and the ends of the star windings are all tied to each other, and do not connect to any other power lead. (this effectively halves the number of poles and makes the motor run faster)
Switching is accomplished by hardinge in a variety of ways. My milling machine for example has a single drum switch with six rotors in it, and each rotor has internal connections such that the three wipers on one side of the switch are correctly commutated to the six wipers on the other side. This thing has a vaguely enigma-like quality and it took me about three nights of sweating before I married it to the motor and got it all wired up right. It's not the stock drum control for that machine btw.
In my DSM-59 they do it in another way: here is a photograph of the switchgear for that machine:
<
http://www.metalworking.com/DropBox/_2001_retired_files/DSM5.jpg
Wherein you will see two separate drum controllers. The right hand one is the normal forward/off/reverse type. The black disks on the shafts are cams, and the bottom-most cam actuates its switch in both positions, the upper two pairs operate alternately in forward and reverse, and serve to reverse the two remaining incoming lines.
The left hand drum controller does the speed control. Unfortunately I took the photo from the wrong side so you cannot get a good view of the jumpers on the extreme left side of the switches, but one can see that the wires that enter into the switches from the left are (top to bottom) white, black, white; and white, black, white; and then at the very bottom they are again white black white.
The lowest trio is there, take it on faith. :)
The black wires are the incoming power lines (suitably rendered by the reversing switch) and the white leads are the motor wires, which go off in greenfield conduit to the motor itself.
If one were to label the cams, top to bottom, as 1 to 8, they operate as follows.
High speed, cams 1, 3, 4, 6 and 8 actuate their switches.
Low speed, cams 2, 5, and 7 actuate their switches
The reason that the high speed has two extra cams, is so that the ends of the star windings can be all tied together. Otherwise the contactors either choose incoming lines to go to either 'ends' or 'centertaps' of each motor winding.
This is a good deal more complicated in the telling, than in the reality. There is also a good schematic on the inside of the door cover if anyone wanted a snapshot of it.
Jim
================================================= please reply to: JRR(zero) at yktvmv (dot) vnet (dot) ibm (dot) com ================================================
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