Toolmaster 1B Variable Frequency Drive
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    Default Toolmaster 1B Variable Frequency Drive

    I am the lucky owner of a Toolmaster 1B. It has step V belt pulleys & a hi/lo Cog belt. It also has the original pancake spindle motor. The mill is in great shape and machines very well. I am getting tired of fooling with the belts to change spindle speeds so I'm considering a VFD. I have a few questions:

    Will the pancake motor work fine with a VFD?

    Would I set the belts in the max speed position and leave it there?

    If pulleys are set at max speed position, Will the setup have enough cutting torque at lower spindle rpm for larger cutters & drills?

    Will the pancake motor need some fan cooling?

    Thanks for your input.

    Regards,
    Steve

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    If you can, take a picture of the motor’s specification label and post it here. That will help those with the required knowledge know what you have.

    All I can add is that you will love having a VFD on your machine.

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    Only if it is a three phase motor.
    Bill D

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    Quote Originally Posted by Bill D View Post
    Only if it is a three phase motor.
    Bill D
    Yes, It's 220V 3 phase I'll get a pic of the motor

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    The VFD should not cause any issues with the motor. I have installed VFDs to drive ancient motors with no problems whatsoever. This includes a 1943 Delta drill press with a 3/4-HP motor, a 1963 Colchester Chipmaster with a Brook Crompton 3-HP motor, a 1970s Taiwanese Bridgport clone, a 1960s Deckel Pantograph, and a 1960s Bridgeport with a 1-HP Fairbanks Morse pancake motor.

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    Quote Originally Posted by SABToolmaster View Post
    I am the lucky owner of a Toolmaster 1B. It has step V belt pulleys & a hi/lo Cog belt. It also has the original pancake spindle motor. The mill is in great shape and machines very well. I am getting tired of fooling with the belts to change spindle speeds so I'm considering a VFD. I have a few questions:

    Will the pancake motor work fine with a VFD?

    Would I set the belts in the max speed position and leave it there?

    If pulleys are set at max speed position, Will the setup have enough cutting torque at lower spindle rpm for larger cutters & drills?

    Will the pancake motor need some fan cooling?

    Thanks for your input.

    Regards,
    Steve
    I like many people I expect put a 1HP bridgeport J-head onto a VFD, probably similar to your motor. I wired the forward/stop/rev switch to the VFD controls, and then also installed a potentiometer for
    speed control.

    I can therefore vary the speed in any pulley position from 0 RPM to max. I generally
    switch the belt for operations where I really want the full RPMs or torque, but otherwise
    use the analog speed control but not normally at the very low end of the RPM range.

    It is very nice to be able to try tooling with infinitely variable speed, such as a fly cutter or boring head, etc.

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    Here's a photo of the motor and the nameplate.img_2726.jpgimg_2728.jpgimg_2729.jpg

    I would probably run the belts in the 1700RPM position. I rarely would need 2825 RPM

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    Ran one for years on an almost exact motor. Mine was 1 hp not 3/4. The motor never failed.

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    Quote Originally Posted by markz528 View Post
    Ran one for years on an almost exact motor. Mine was 1 hp not 3/4. The motor never failed.
    Thank you for the input.

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    You will lose Hp below the motor's base speed, so may be a bit anemic if you go below something like 30Hz. Older motors I tend to be a more conservative in the carrier frequency and RPM range. Since this is an 8P motor I would suggest something like 30-90 Hz, and a carrier frequency of something in the 2-4 kHz range. Cooling would not be an issue in this speed range. I have heard a few of these pancake motors failing when run of VFD's, so YMMV.

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    Quote Originally Posted by mksj View Post
    You will lose Hp below the motor's base speed, so may be a bit anemic if you go below something like 30Hz. Older motors I tend to be a more conservative in the carrier frequency and RPM range. Since this is an 8P motor I would suggest something like 30-90 Hz, and a carrier frequency of something in the 2-4 kHz range. Cooling would not be an issue in this speed range. I have heard a few of these pancake motors failing when run of VFD's, so YMMV.
    So at 90Hz, are you suggesting that I spin the motor faster than the original rating? Need to look in to the carrier frequency comment to understand that.

    Regards,
    Steve

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    Quote Originally Posted by SABToolmaster View Post
    So at 90Hz, are you suggesting that I spin the motor faster than the original rating? Need to look in to the carrier frequency comment to understand that.

    Regards,
    Steve
    He is saying don't use the speed adjustment outside a range of 30-90 Hz.

    Carrier frequency is something altogether different. Visualize the typical sine curve you see on a graph or oscilloscope for pure AC from the wall or a generator. It is smooth with no gradations, an analog curve. Carrier frequency is basically how many steps will be in this curve when the VFD synthesizes the digital AC curve. So instead of a nice smooth curve, you will get tiny stair steps as you go along the curve. Carrier frequency is how many of these steps per second you have. So for instance if you have a very low carrier frequency the curve would look very blocky. If you have a high carrier frequency it looks much smoother.

    Lower carrier frequency has benefits as it doesn't tend to set the motor windings to vibrating as much. This is good for longevity in older motors. Higher frequency has benefits in that it makes the motor run smoother and somewhat quieter. Older motors not made for inverter user should probably be run with as low a carrier frequency as possible.

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    Quote Originally Posted by eKretz View Post
    He is saying don't use the speed adjustment outside a range of 30-90 Hz.

    Carrier frequency is something altogether different. Visualize the typical sine curve you see on a graph or oscilloscope for pure AC from the wall or a generator. It is smooth with no gradations, an analog curve. Carrier frequency is basically how many steps will be in this curve when the VFD synthesizes the digital AC curve. So instead of a nice smooth curve, you will get tiny stair steps as you go along the curve. Carrier frequency is how many of these steps per second you have. So for instance if you have a very low carrier frequency the curve would look very blocky. If you have a high carrier frequency it looks much smoother.

    Lower carrier frequency has benefits as it doesn't tend to set the motor windings to vibrating as much. This is good for longevity in older motors. Higher frequency has benefits in that it makes the motor run smoother and somewhat quieter. Older motors not made for inverter user should probably be run with as low a carrier frequency as possible.
    That is an excellent explanation of carrier frequency! It makes total sense to me. Also, a reputable drive supplier commented that carrier frequency choice may be influenced by the length of the wire between the drive and the motor.

    The motor is rated at 860 RMP at 60Hz. So, if I run the frequency up to 90, the motor should run about 1290 or so depending on slip.

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    A carrier frequency equal to 5khz that is generating a 60hz waveform.

    dsc_0881.jpg

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    Yeah carrier frequency too high or long motor lines can cause reflections. There's some more good info at this link:

    How to Choose a General Purpose Motors vs Inverter-Duty Motors

    The waveform for voltage from the VFD doesn't look like the typical sine wave at all, but if you look at the current waveform you'll see more of the typical jagged sine wave shape I was talking about earlier. That's more what the motor "sees" versus what the o'scope shows.

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    Quote Originally Posted by mksj View Post
    You will lose Hp below the motor's base speed, so may be a bit anemic if you go below something like 30Hz. Older motors I tend to be a more conservative in the carrier frequency and RPM range. Since this is an 8P motor I would suggest something like 30-90 Hz, and a carrier frequency of something in the 2-4 kHz range. Cooling would not be an issue in this speed range. I have heard a few of these pancake motors failing when run of VFD's, so YMMV.
    While an accurate statement, it's bit misleading. The reduced RPM is a reduction in HP (because HP is a function of RPM and TQ) but not a reduction in torque. The motor will make full torque into really low RPM.

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    Quote Originally Posted by Cole2534 View Post
    While an accurate statement, it's bit misleading. The reduced RPM is a reduction in HP (because HP is a function of RPM and TQ) but not a reduction in torque. The motor will make full torque into really low RPM.
    Thanks for the reply. It's all about torque IMO.

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    Quote Originally Posted by Cole2534 View Post
    While an accurate statement, it's bit misleading. The reduced RPM is a reduction in HP (because HP is a function of RPM and TQ) but not a reduction in torque. The motor will make full torque into really low RPM.
    Older motors probably have a constant torque of 2:1, newer (non-inverter) motors 4:1, so most likely you will loose torque below 20-30Hz. Torque of the motor is probably not reduced at 30 Hz, but you loose the mechanical advantage you would have with the same motor at 60Hz with a 2:1 reduction, so you loose both torque by a factor of 2 and Hp by a factor of 4 at the spindle. So yes, the motor will be anemic below 30 Hz. An older motor also cannot be pushed hard in comparison to an inverter motor so you might have an overload of 100-120% for an old motor, I usually use 150-180% for an inverter rated motor. The 3 Hp inverter motor on my mill runs from 20-200Hz, so optimized for higher speed.

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    Quote Originally Posted by mksj View Post
    1. Older motors probably have a constant torque of 2:1, newer (non-inverter) motors 4:1, so most likely you will loose torque below 20-30Hz.
    2. Torque of the motor is probably not reduced at 30 Hz, but you loose the mechanical advantage you would have with the same motor at 60Hz with a 2:1 reduction, so you loose both torque by a factor of 2 and Hp by a factor of 4 at the spindle. So yes, the motor will be anemic below 30 Hz.

    3. An older motor also cannot be pushed hard in comparison to an inverter motor so you might have an overload of 100-120% for an old motor, I usually use 150-180% for an inverter rated motor. The 3 Hp inverter motor on my mill runs from 20-200Hz, so optimized for higher speed.
    1. Ive never read that, if you have some links I'd like to the see theme.

    2. This isn't about mechanical advantage, not sure why you brought it up.

    3. That's covered in the service factor and is motor specific, it should be on the nameplate.

    Sent from my SM-G973U using Tapatalk

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    He mentioned loss of mechanical advantage because the O.P. stated that he wanted to leave the machine in high range and use the VFD to reduce speed rather than changing the belts/pulleys. Hence, lost mechanical advantage.


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