Rewiring a Hardinge TBF for VFD control
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    Default Rewiring a Hardinge TBF for VFD control

    Hi
    We have a 1959 TBF and want to remove as much of the original control gear as possible.
    Someone in the past has fitted a 20v dc motor for the speed control.
    As the spindle motor is two speed via the handle/rotary switch set up, is it ok to include this in the motor supply from the VFD on the understanding that the spindle must be stopped before throwing the lever?
    Secondly can the 110v feed for the power feed motor be taken off the VFD?
    Thirdly what is the best course of action to control the speed change motor?

    Many thanks in advance
    Lee

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    I'm not sure I understand your setup. Is the 20vdc motor your power feed motor?

    What's your spindle motor? If you're planning to run a vfd, the motor needs to be a 3 phase ac motor with the correct voltage range for the vfd.

    It's best practice not to have any switches between your vfd and your motor. If a switch gets inadvertently thrown while the motor is running (even once), it risks letting the magic smoke out. Difficult to put that back in. No sense in maintaining an electrical "low speed" option - the VFD achieves the same thing with a turn of the speed pot.

    As far as I'm aware, you can't pull 110v from anywhere on a vfd. You might be able to pull 110v from the 220v supply before it enters the vfd, but you would need a neutral as well. I'll not sure I would want to do that - easier just to run a second cord to the 110v outlet.

    Sent from my SM-N960U using Tapatalk

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    Hi
    The spindle motor is the Hardinge 2 speed.
    Ok, so just wire to the high speed motor windings on the spindle motor from the VFD.
    We can run a separate 110v for the speed control via a step down transformer for the 20v motor. I have tested that motor separately.
    And the separate 110v will supply the carriage feed.

    Many thanks
    Lee


    Quote Originally Posted by leeko View Post
    I'm not sure I understand your setup. Is the 20vdc motor your power feed motor?

    What's your spindle motor? If you're planning to run a vfd, the motor needs to be a 3 phase ac motor with the correct voltage range for the vfd.

    It's best practice not to have any switches between your vfd and your motor. If a switch gets inadvertently thrown while the motor is running (even once), it risks letting the magic smoke out. Difficult to put that back in. No sense in maintaining an electrical "low speed" option - the VFD achieves the same thing with a turn of the speed pot.

    As far as I'm aware, you can't pull 110v from anywhere on a vfd. You might be able to pull 110v from the 220v supply before it enters the vfd, but you would need a neutral as well. I'll not sure I would want to do that - easier just to run a second cord to the 110v outlet.

    Sent from my SM-N960U using Tapatalk

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    Default Speed control motor

    Is there a simpler way to run the speed control motor. Not sure how to use the original 1956 contractor set up.
    There are fast-slow switches mounted above the headstock and cut off switches at the motor junction box.

    Thanks
    Lee




    Quote Originally Posted by leeko View Post
    I'm not sure I understand your setup. Is the 20vdc motor your power feed motor?

    What's your spindle motor? If you're planning to run a vfd, the motor needs to be a 3 phase ac motor with the correct voltage range for the vfd.

    It's best practice not to have any switches between your vfd and your motor. If a switch gets inadvertently thrown while the motor is running (even once), it risks letting the magic smoke out. Difficult to put that back in. No sense in maintaining an electrical "low speed" option - the VFD achieves the same thing with a turn of the speed pot.

    As far as I'm aware, you can't pull 110v from anywhere on a vfd. You might be able to pull 110v from the 220v supply before it enters the vfd, but you would need a neutral as well. I'll not sure I would want to do that - easier just to run a second cord to the 110v outlet.

    Sent from my SM-N960U using Tapatalk

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    I have a hardinge TM mill with a 2 speed motor. I wanted continuously variable speed, so I wired a vfd to the high speed winding as you mentioned. I'm not aware of any simpler/better ways to do it, but working a VFD is fairly straightforward in most cases.

    Lee

    Sent from my SM-N960U using Tapatalk

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    On an original 230 volt 3-phase machine:

    The speed control motor (for the variable sheave drive), spindle motor (2-speed controlled by the contactors and connections) and pump are all 230v 3-phase.

    The carriage motor is 90 volts dc (fed from the carriage motor control box which has 115 volt input from the 230-115 volt transformer).

    Controls/relays are 115 vac

    Solenoid brake is DC fed from 115 volt rectifier circuit.

    VFD's are suitable for running only one motor at a time, should not be switched on the output side of the VFD, and will not supply 230 or 115 volt single-phase on the output.

    The above is why it is not convenient to rewire an HLV (the best solution for an intact machine is a rotary phase converter). In fact, you can't plop a VFD as an input to an OEM machine since there are multiple 3-p motors, and the need for 230 volt single-phase to the control-transformer. So you basically have to scrap the original controls and do a fair amount of wiring.

    You indicated that the speed control motor had already been swapped from the oem 3-p to a 20vdc. It should be possible to use the existing switch functions and even the lever controls (ignoring all the 115v relays, and just using the switches) but it will take a fair amount of wiring and figuring out connections.

    The schematics of the OEM setup have been posted a few times here.

    Quote Originally Posted by Dunedin View Post
    Is there a simpler way to run the speed control motor. Not sure how to use the original 1956 contractor set up.
    There are fast-slow switches mounted above the headstock and cut off switches at the motor junction box.

    Thanks
    Lee

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    Hi
    I have a vfd running the spindle motor only using the higher speed windings.
    The old relays and main contractors where shot.
    The feed for the carriage slide is 110v and that’s working fine.
    Having taken the motor plate off I found someone had turned it into spaghetti! Connections taped up and screw on terminals falling off.

    To use the speed control motor I have fitted a transformer 110v-20v DC. It’s tested and working.

    What I need to figure out is how to hook up your Fast-Slow controls. The contractors use a 110v supply for the coil and only engage when you hold the button in. Cutoff switches are in the circuit to stop the motor over running.

    Thankfully the wiring diagram is still there.
    Hopefully we can also get a remote unit for the VFD with a potentiometer. Although the older motor would not do well running at very slow speeds.

    It’s a beautiful machine.

    Cheers
    Lee

    Quote Originally Posted by car2 View Post
    On an original 230 volt 3-phase machine:

    The speed control motor (for the variable sheave drive), spindle motor (2-speed controlled by the contactors and connections) and pump are all 230v 3-phase.

    The carriage motor is 90 volts dc (fed from the carriage motor control box which has 115 volt input from the 230-115 volt transformer).

    Controls/relays are 115 vac

    Solenoid brake is DC fed from 115 volt rectifier circuit.

    VFD's are suitable for running only one motor at a time, should not be switched on the output side of the VFD, and will not supply 230 or 115 volt single-phase on the output.

    The above is why it is not convenient to rewire an HLV (the best solution for an intact machine is a rotary phase converter). In fact, you can't plop a VFD as an input to an OEM machine since there are multiple 3-p motors, and the need for 230 volt single-phase to the control-transformer. So you basically have to scrap the original controls and do a fair amount of wiring.

    You indicated that the speed control motor had already been swapped from the oem 3-p to a 20vdc. It should be possible to use the existing switch functions and even the lever controls (ignoring all the 115v relays, and just using the switches) but it will take a fair amount of wiring and figuring out connections.

    The schematics of the OEM setup have been posted a few times here.

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    Quote Originally Posted by Dunedin View Post
    To use the speed control motor I have fitted a transformer 110v-20v DC. It’s tested and working.
    Taking note that 120 VAC input generally powers a DC motor at but 90 VDC after rectification or DC Drive, 180 VDC off 230 VAC, the 20 VDC motor may actually have wanted at least a 24 VAC if not 28 VAC input for full power and speed.

    Which I don't see you actually NEED when patience for slower action is "free".

    OTOH, Center-tapped 24 VAC transformers are common. And there might be your least-complex and least-cost source for High and Low speed operation.

    Wire it so high speed is the full 20 VDC - or whatever it actually is, Then switch the AC input to half the transformer output Voltage for low speed @ roughly half the VDC to the motor.

    AC is cheaper to switch, "mechanically" as there is a rise and fall Sine wave that rarely hits peak current flow at any given "time" of close or open, either one. Lighter contacts will do, and still last longer than the contacts wanted to endure DC disconnect arcs, where flow is ALWAYS at the full power, regardless of time of disconnect. No helpful - or pesky - sine wave involved. or at least one that is controllable. But see "DC Drive", and "4Q" or regenerative most of all. Not that you need one.

    If still too fast, or if no desire to mess with another transformer, consider hard-wiring a high-current, heat tolerant and/or heat SINKED (finned, even) resistor in series with the Armature. A "braking" resistor is where you find the goods for sale, Galco and many other of similar product line.

    That will be "low" speed.

    Now "shunt", or bypass the resistor with the existing contactor. That will be "high" speed.

    Not hard. Not expensive. Not even all that space-greedy. Not all that hot, thermally, either, as it is only powered AT ALL when calling for a move.

    Unlike AC, "frequency" sensitive as to RPM, DC motors are Voltage-sensitive current-mode "integrators", hence inherently variable speed animals. Even when you would rather they were NOT! See DC drives, plus tachogenerator feedback to make them mind their manners as to stable RPM. Very stable. Just not the same as "cheap".


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    Quote Originally Posted by Dunedin View Post
    Hi
    I have a vfd running the spindle motor only using the higher speed windings.
    The old relays and main contractors where shot.
    The feed for the carriage slide is 110v and that’s working fine.
    Having taken the motor plate off I found someone had turned it into spaghetti! Connections taped up and screw on terminals falling off.

    To use the speed control motor I have fitted a transformer 110v-20v DC. It’s tested and working.

    What I need to figure out is how to hook up your Fast-Slow controls. The contractors use a 110v supply for the coil and only engage when you hold the button in. Cutoff switches are in the circuit to stop the motor over running.

    Thankfully the wiring diagram is still there.
    Hopefully we can also get a remote unit for the VFD with a potentiometer. Although the older motor would not do well running at very slow speeds.

    It’s a beautiful machine.

    Cheers
    Lee
    The simple way to reverse the DC motor is with a DPDT switch (plenty of examples available by searching "DC motor reversing switch"); you can get one that's spring-loaded to the "off" center position (eg. center-off, momentary up, momentary down). (don't know how to use the single-pole momentary switches existing in the pod without a lot of haranguing). Then, the (assuming normally closed) limit-switches just need to be wired into the leg going from the switch to the motor.

    The VFD should be easily wired with a pot for speed control whatever location is convenient (along with on/of, and fwd/rev switches if not using the original switches). The motor probably will do OK at slow speeds with the VFD; as long as it's not run at real slow speeds under a high load for extended times. You can also monitor the temp at different speeds to see if there's any heating. I don't think those motors are fan-cooled, but rely on the massive case. I have three motors with VFD's and have never had an issue with them overheating at slow speeds (granted they're not overtaxed or run for hours at a time). Have fun, Cheers.

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    Quote Originally Posted by car2 View Post
    The simple way to reverse the DC motor is with a DPDT switch (plenty of examples available by searching "DC motor reversing switch"); you can get one that's spring-loaded to the "off" center position (eg. center-off, momentary up, momentary down).
    Seems 'orrible to pay - ISTR it was $25 or more? for what APPEARS to be a three-dollah DPDT Centre-OFF toggle that KB-Penta house-brands, Galco et al sell, but someone else actually MAKES.

    Adding reverse switch to KBAC-27D

    That bit of mechanical jiggery-pokey forces a slight delay when trying for a fast change of direction, reduces the annoyance of an arc-damaged switch and/or fuses blown right in the middle of a job.

    You'd have to know "Dinosaur Current"? Instantly reversible it can be. Just not without its ration of "highly inductive" whiplash drama.

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    You have a VFD to control the speed of the spindle motor.

    Set the varispeed sheaves at midpoint and leave them there.

    Wire the VFD directly to the motor, in the high range.


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