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10EE MG Starter Circuit with Cutler-Hammer Contactor - Revised

Cal Haines

Diamond
Joined
Sep 19, 2002
Location
Tucson, AZ
Problems with the starting circuit are one of the common difficulties that a new owner of a 10EE faces. What follows is an explanation of the 10EE motor-generator (MG) starter circuit for machines equipped with the standard Cutler-Hammer model 9586 contactor.
This is a revised version of a thread that I posted a year ago:
10EE MG Starter Circuit with Cutler-Hammer Contactor
It turns out that the “Typical” or AS-BUILT drawing that I used as a basis for my discussion there wasn’t very typical at all. Rather than create confusion by adding to that thread, I’m reposting the thread here, with updated illustrations and some additional information.
Here is a modified section of the wiring drawing for a round-dial 10EE, drawing EE-2674:
EE-2674 Starting Circuit - Annotated
I’m providing this drawing mostly for historical reasons; you don’t need to bother with it if you’re just trying to understand the starting circuit. To create the drawing I deleted some things (like the speed control rheostats) that don’t pertain to the starting circuit, cleaned it up and added some annotations. I don't know about everyone else, but I found the non-standard symbols used on the drawing very confusing. For example, the contactor's coil is shown by a circle with two terminals (the same symbol is used elsewhere for a light bulb). The transformer symbol looks like two resistors sitting side-by-side, etc. It took me the longest time to make sense of the diagram, so I've annotated the coil, overload heater (one of two) and overload switch (if that's the correct term for it) for reference.

Here is a drawing that I have modified to what I believe is a “typical” circuit as the machines were actually wired:
208455d1506034435-10ee-mg-starter-circuit-cutler-hammer-contactor-revised-10ee-start-circuit-c-h-typical-v2-4b.jpg

The blue lines on the diagram indicate the changes from EE-2674. Again, this diagram is provided solely for reference. You don’t need it for purposes of this discussion. Most MG-driven 10EEs appear to have been wired at the factory with the left side of the coil wired to L1; the other side of the starting circuit and terminal 3, at the top of the contactor, usually connects to L3. The starting circuit should be essentially the same for all 10EEs with MG drive.

Unfortunately, the typical AS-BUILT 10EE starting circuit is not compatible with most Rotary Phase Converters (RPC). RPCs tend to supply most of the power via the two “real” phases which connect directly to the incoming 240 VAC circuit. It’s very important that the “real” phases connect to the L1 and L2 terminals of the of the Cutler-Hammer contactor, since these are the only lines that have over-current protection. The problem with the AS-BUILT configuration of a 10EE starting circuit is that the coil is powered by incoming lines L1 and L3. Since the voltage of an RPC’s “wild” or artificial leg can vary significantly at startup, having it connected to the starting circuit’s coil via L3 can result in the machine failing to start or dropping out under load. The fix for the problem consists of moving a single wire from L3 to L2.

This diagram shows a typical MG starting circuit that has been modified for use with an RPC by moving the jumper that connects the top, right terminal of the contactor from L3 to L2:
208452d1506033100-10ee-mg-starter-circuit-cutler-hammer-contactor-revised-10ee-start-circuit-c-h-annotated-v2-4b.jpg

As before, the blue lines show the connections that differ from drawing EE-2674. The magenta line shows the change made for RPC compatibility. The coil, overload heater and overload switch are also identified. Since this circuit functions equally well for true 3-phase power and for RPC-powered systems, it will be the basis for further discussions.

Note the following changes from EE-2674: 1) the left terminal of the coil connects to L1, not to the overload switch; 2) the right terminal of the coil connects to the right terminal of the overload switch rather than the STOP switch; 3) the left terminal of the overload switch connects to the STOP switch; 4) terminal 3, top right on the contactor, connects to L2.

One thing that is helpful to know about the diagram is that the relative positions of the terminals on the contactor are the same as those on the actual unit. Here is a photo of a 10EE Cutler-Hammer contactor with the same annotations, for reference:
C-H Contactor EE24647_18 Anno.jpg
Some contactors label the upper right terminal 1 instead of 3. I am using 3 here for consistency with drawing EE-2674.

Here is another photo of the same contactor, showing the overload section in more detail:
C-H Contactor EE24647_20 Anno 5.jpg
Terminals T1, T2 and T3 provide power to the MG. Terminals T1-1, T2-1 and T3 are typically used for connecting the coolant pump (if the machine is so equipped); this keeps the coolant pump from tripping the overloads when the machine is operating at full power, but also means that the coolant pump operates without overload protection.

Now we turn our attention to how the starting circuit operates. Below is an version of the above diagram, showing the coil circuit at startup, when the (momentary contact) START button is pressed:
208453d1506033843-10ee-mg-starter-circuit-cutler-hammer-contactor-revised-10ee-start-circuit-c-h-start-v2-4b.jpg

Tracing the magenta wires, we see that the startup circuit is completed as follows: AC input L2 (and terminal 3, upper right) connect to the center position contacts of the drum switch in the headstock (which must be in the center position to allow the MG to start). The headstock switch is connected to terminal 3 of the START/STOP station (located on the right side of the "bump out" on the base); the START switch is a normally open, momentary contact switch and must be pressed by the operator to initiate startup. START switch terminal 1 is wired to STOP switch terminal 1. The STOP switch is normally closed and must be closed to allow startup. Terminal 2 of the STOP switch is, in turn, wired to the overload switch on the bottom of the contactor. If an over-current occurs on either L1 or L2, the thermally-operated overload switch will open and must be manually reset by pressing the overload reset button on the contactor; the overload switch must be closed/reset to allow startup. The other side of the overload switch is wired to one terminal of the coil. The other terminal of the coil is connected to L1, completing the circuit. Note that if there is an interruption in any portion of the red and magenta lines, above, the coil will not be energized and the MG will not start.

A lot of people are intimidated by 3-phase power and controls; don’t be. If you understand basic circuits, such as household wiring, you can understand the 10EE starting circuit. Think of it as a lighting circuit with the coil as the light bulb. All four (series connected) switches must be closed in order for the “light bulb” to operate. The four switches are: 1) headstock center-position switch; 2) START button; 3) STOP button; and, 4) overload switch.

When the coil is energized by completing the starting circuit the large 4-pole main relay at the top of the contactor closes. The contacts on the right end (terminals 3 and 1) now provide voltage directly to terminal 1 on the START/STOP station, bypassing the START and headstock switches and keeping the coil energized, as shown in the diagram below. If either the overload switch or the STOP switch open, the circuit is interrupted, the coil looses power, the contactor will open and the MG will shut down. This diagram shows the coil circuit with main contacts closed:

Using the household circuit analogy again: now the “light bulb” (coil) is powered by three switches in series: 1) the contacts on the right end of the main relay; 2) the STOP button; and, 3) the overload switch. Pressing the STOP button interrupts the circuit, the “light bulb” looses power, and the MG shuts down.
208454d1506033862-10ee-mg-starter-circuit-cutler-hammer-contactor-revised-10ee-start-circuit-c-h-run-v2-4b.jpg


The starting circuit for a MG-equipped 10EE with an Allen-Bradley contactor is shown in this thread: 10EE starting circuit with Allen-Bradley contactor

As always, corrections, clarifications and questions are very welcome.

Cal
 

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Cal, Thanks for posting this. It was exactly what I needed to get my machine to start with my rpc. Very straight forward advice. Chuck
 
Two questions on this subject:

1) What would cause the coil to not pull the contactor? If I push it by hand, it engages and starts. It buzzes but won't pull it in.

2) Once I push it manually and get it running. The spindle runs in reverse. If I reverse it, it runs forward.

Any suggestions would be appreciated.

Thanks,
Bob
 
Two questions on this subject:

1) What would cause the coil to not pull the contactor? If I push it by hand, it engages and starts. It buzzes but won't pull it in.

2) Once I push it manually and get it running. The spindle runs in reverse. If I reverse it, it runs forward.

Any suggestions would be appreciated.

Thanks,
Bob
Hi Bob,

Welcome aboard! Sorry to not responding sooner, I've been out of town and just returned last night.

When you post here it's always a good idea to let us know the model of the machine that you have, the type of the drive, and any accessories that you have. For example (for a 10EE): 10EE; round or square dial model; MG or WIAD or Modular (or retrofit) drive; accessories such as coolant pump and ELSR (Electric Lead Screw Reverse).


This kind of problem can have several causes:
  1. Bad coil
  2. Wrong coil
  3. RPC (Rotary Phase Converter) connected incorrectly
  4. Open or bad connection in the starting circuit
Since the contactor is buzzing but not engaging when you press the start button, you probably don't have any problems with the starting circuit switches and wiring. Since it will stay engaged when you push the main relay closed by hand we know that the portion of the start circuit that is common to the run circuit is OK; that is, the STOP switch, the overload switch and any additional interlocks are conducting. But just to be sure, check the voltage across the coil while the START button is pressed; on most machines you should see 240 VAC (assuming that you are working from 240 VAC source).

I suspect that you have one of the first 3 problems, lets check the following:
Is there a tag on the coil. If so, what does it read? (A 440 Volt coil will hold the relay closed, but won't have enough EMF to pull the relay in.)

Are you using an RPC? If so, have you verified that the "real" legs of the RPC are connected to L1 and L2? Is the right hand (#3) terminal connected to L2 and not L3? (The AS-BUILT configuration is for the jumper from terminal 3 to connect to L3, which often causes starting problems like yours with an RPC).
Cal
 
Cal,

You nailed it. The coil is a 440v. The resistance of the coil is 675 ohms, does that sound right? Forum member Regina's 220v coil measured 150 ohms.

Any ideas on where to find a 220v coil?


for the record I have a 1958 10EE Round dial, MG, with coolant pump.

Thanks,
Bob
 
... Any ideas on where to find a 220v coil?
Try Brazil Electric, 503-227-4973. I've never done business with them, but people here recommend them and they seem to have good stock. If you have a 440V coil, the chances are that you have the wrong heaters on the overload device. This will result in the overload tripping at 50% of full load current, or about 25% of full power.

Here's a thread that discusses heater coils:
http://www.practicalmachinist.com/vb/monarch-lathes/wtb-heater-coils-c-h-contactor-h-1374-a-173812/

There are a couple of ways to use a 440V coil with 240V, but you are better off with the right coil and heaters.

for the record I have a 1958 10EE Round dial, MG, with coolant pump.
Are you sure about that? As far as I know, the last round-dials were built in early 1945. What's your serial number?

Cal
 
Cal,

My serial # is 43201. The plate says manufactured in 1958. Maybe I'm confused on the "round dial" term. What does that refer to?

The heaters in it are H1399. I have a spare set of H1374. It looks like the 1374's are for 440v. Not sure what the H1399's are. I'll be calling Brazil Electric in the morning.

Thanks for the help,
Bob
 
Bob,

In getting my '43 lathe going there was a discussion about the heaters. It revealed the H1374's were for 220v @ 14.7 - 15.8 amps. Here's a link to it.

1943 Round Dial

Bob
 
... My serial # is 43201. The plate says manufactured in 1958. Maybe I'm confused on the "round dial" term. What does that refer to? ...
You have a square-dial machine. The round vs. square business refers to the shape of the data plate, with the feed and thread combinations on it, that is on the quick-change gearbox.

Cal
 
uploading additional images to fix broken photobucket images
 

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