Cal Haines
Diamond
- Joined
- Sep 19, 2002
- Location
- Tucson, AZ
A member contacted me by PM asking for a list of things to do when converting a motor generator (MG) drive 10EE from 440 to 220. Since this question comes up from time to time, I decided to put the checklist here on the forum, where future users can find it.
If you look carefully you can see that this contactor has a 440 Volt coil.
- Verify that the machine can be converted to 220. A few 10EEs were built with single voltage motors and a few were built with 2-phase motors. (2-phase power was used in the Niagara Falls area in the early to mid 1900s.) Check the data plate on the left (headstock end) of the MG. Remove the cover on the front (operator’s side) of the lathe, at the operator’s feet and look on the body of the unit behind and to the side of the terminal box. If the plate lists both 220 and 440 Volts the motor can be converted to 220.
Typical MG from a later model round-dial 10EE with piggyback exciter:
The location of the MG’s data plate is outlined in red.
Data plate:
The area of the plate showing the possible operating voltages is marked in red. Note also the direction of rotation arrow and the diagrams showing connections for 220 and 440 Volt operation.
Typical square-dial MG with data plate outlined in red:
Data plate with voltage data outlined in red:
The location of the MG’s data plate is outlined in red.
Data plate:
The area of the plate showing the possible operating voltages is marked in red. Note also the direction of rotation arrow and the diagrams showing connections for 220 and 440 Volt operation.
Typical square-dial MG with data plate outlined in red:
Data plate with voltage data outlined in red:
- See what voltage the motor is currently wired for. DaveE wrote a very clear explanation of how to check the current wiring:
* T4 is sometimes used on 220 Volt machine as a place tie the three leads together, but they are usually connected together and insulated.
If you look closely at the MG photos above you will see that the round-dial MG it is wired for 220/240 volt operation and the square-dial MG is wired for 440/480 operation.
- If necessary, change the connections. All 9 wires should have tags identifying the wire’s number. If there is a plate on the motor showing the connections for 220 Volts, use it as a guide for connections. If there is no plate, connect as follows: Wires 1 & 7 to terminal T1; wires 2 & 8 to T2; wires 3 & 9 to T3. The remaining three wires, 4, 5 and 6, are connected together, either by connecting them to terminal T4 or by fastening them together with a wire nut or small fastener and insulating with electrical tape.
- Verify that the main contactor has a 220 Volt coil. The main contactor is located behind a cast cover on the back of the machine, behind the quick change gearbox. The original Cutler-Hammer (C-H) bulletin 9586 contactor usually has the voltage marked on top of the coil (see photo). You can get a replacement coil from Brazil Motors & Controls [Portland, OR (503) 227-4973].
If you look carefully you can see that this contactor has a 440 Volt coil.
- Verify that the overload heaters are the correct size. The original contactor used overload devices on two of the three incoming phases. The heater sets the current at which the overload device will trip. The heater number should be on a copper tag attached to each heater coil. Heater numbers H1374 and H1375 are OK for 220/240V operation. When wired for 440 operation, the MG draws about half the current that it does at 220/240, so the overload may trip unnecessarily under heavy loads if the heaters are not changed. (Using 440 heaters on a 220 machine won’t damage anything, but you may have to deal with them tripping, depending on how heavily you use the machine.) Brazil can also supply replacement overload heaters.
- If operating from a Rotary Phase Converter (RPC), change the C-H contactor’s coil so that it operates from L1 and L2. (Typical factory wiring used L1 and L3.) Connect the RPC’s “real” legs to L1 and L2, where they will be protected by the overload circuit; the “wild” leg should be on L3 since it usually provides less current. For more information, see this thread: 10EE MG Starter Circuit with Cutler-Hammer Contactor
If you look closely at the photo of the contactor, above, you can see a grey wire running across the top of the contactor, below the word "Coil". The wire connects terminals 3 and L3 on the contactor, thus it is NOT properly setup for use with an RPC; the wire needs to move from L3 to L2.
- Verify that the fuses in the external disconnect box, if any, are the correct size. Most 10EEs will have an electrical disconnect box mounted on the back of the machine, near the floor. These usually have a 3-phase knife switch and fuses for the 3 phases. 30A fuses are OK for 220/240 Volt operation.
- When you start the MG the first time, shut it down immediately and note which direction it’s turning. There is usually an arrow on the case of the MG that shows the direction of rotation; make sure that it’s turning in that direction or you will damage the brushes. (As far as I know, all MG sets turn clockwise, when viewed from the tailstock end.) If the MG is turning in the wrong direction, swap L1 and L2.
- Check the output voltage of the exciter across terminals E1 and E2. It should be 115 Volts DC on most machines (some older machines used 230 VDC excitation). If the output of the exciter is very low the exciter may need to be “flashed”. If its too low or too high the exciter’s shunt resistor may need to be adjusted. These topics are covered elsewhere.
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