Re: [Emc-users] Spindle Voltage?
On Tue, Nov 3, 2015, at 09:41 AM, Todd Zuercher wrote: > I recently purchased an inexpensive router spindle off of ebay. It is rated > at 6kw and 380v 3ph. The old spindle I'm replacing was dual voltage and could > be wired Y or delta, for 200-240 or 380-460 (7HP). Stupid me I didn't think > to check the old VFD and it is only capible of low voltage (running 208 3ph). > > So my question, what are the repercussions of feeding this motor with only > 208 3ph? > > If the only problem is a loss of a percentage of power, but not more than > half, I can live with that. (It cost less than 1/3 the price of the > original.) > If you keep the same voltage-to-frequency ratio and maximum current the motor will be happy. But of course the speed will be lower. For example, if it is designed for 380V, 240Hz, 14,400RPM, the volts-per-hertz ratio is 380/244 = 1.5833. If the VFD can only deliver 208V, then you will be limited to 208/1.5833 = 131Hz, and the top speed will be 7860 RPM. It will still deliver rated torque at rated current, but since the speed is lower the kW will be lower - only about 3.8kW. You can run it at a lower voltage-to-frequency ratio, but you won't get the same torque. For example you could run it at 208V and 240Hz. You would get a no-load speed of 14,400RPM, but the torque- per-amp will be lower - you'll still only get 3.8kW. -- John Kasunich jmkasun...@fastmail.fm -- ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Spindle Voltage?
It depends. For an asynchronous motor lower voltage will mean lower available torque although it is technically possible to get full torque up to there 208 volt is needed for full power but only if the inverter deliver 208 volt at this point. For a synchronous permanent magnet motor voltage is needed to get the rpm up although it may be possible to weaken the magnetic field to get rpm up. Nicklas Karlsson On Tue, 3 Nov 2015 09:41:37 -0500 (EST) "Todd Zuercher"wrote: > I recently purchased an inexpensive router spindle off of ebay. It is rated > at 6kw and 380v 3ph. The old spindle I'm replacing was dual voltage and could > be wired Y or delta, for 200-240 or 380-460 (7HP). Stupid me I didn't think > to check the old VFD and it is only capible of low voltage (running 208 3ph). > > So my question, what are the repercussions of feeding this motor with only > 208 3ph? > > If the only problem is a loss of a percentage of power, but not more than > half, I can live with that. (It cost less than 1/3 the price of the > original.) > > -- > > > > Todd Zuercher > mailto:zuerc...@embarqmail.com > > > -- > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users -- ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Spindle Voltage?
On Tue, Nov 3, 2015 at 10:02 AM, John Kasunichwrote: > But of course the speed will be lower. For example, if it is designed for > 380V, 240Hz, 14,400RPM, > the volts-per-hertz ratio is 380/244 = 1.5833. If the VFD can only > deliver 208V, then you will be > limited to 208/1.5833 = 131Hz, and the top speed will be 7860 RPM. It > will still deliver rated torque > at rated current, but since the speed is lower the kW will be lower - only > about 3.8kW. > It's not my specialty so I am trying to go over the numbers methodically---please check if I am getting it right. At nominal 380V the thing runs at 6kW6kW * 208/380 and 60*240 Hz, i.e. 14400 rpm. At 208V it should do 208/380*14400, or 7880 rpm, close enough. But for power, P=omega*T, 6kW * 208/380, or 3.28 kW. amirite? -- ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Spindle Voltage?
The VFD is an old EMS G3+ (Yaskawa) drive. The old motors were 200-240v(or 380-460v), 18,000rpm, 7hp. When running the old motors they were drawing about 5-7amps when running at 300Hz. The new motor's tag says 380v, 18,000rpm, 6kw and when running with the VFD set to 300Hz shows about 2 amps current draw. The first test cut with a 1/4" down spiral through two layers of 1/4" MDF (200ipm feed) has no audible drop in rpm, and the VFD shows about 2.5 amps. I think it looks good enough for me. - Original Message - From: "Karlsson & Wang" <nicklas.karls...@karlssonwang.se> To: "Enhanced Machine Controller (EMC)" <emc-users@lists.sourceforge.net> Sent: Tuesday, November 3, 2015 11:15:33 AM Subject: Re: [Emc-users] Spindle Voltage? > On Tue, Nov 3, 2015, at 09:41 AM, Todd Zuercher wrote: > > I recently purchased an inexpensive router spindle off of ebay. It is rated > > at 6kw and 380v 3ph. The old spindle I'm replacing was dual voltage and > > could be wired Y or delta, for 200-240 or 380-460 (7HP). Stupid me I didn't > > think to check the old VFD and it is only capible of low voltage (running > > 208 3ph). > > > > So my question, what are the repercussions of feeding this motor with only > > 208 3ph? > > > > If the only problem is a loss of a percentage of power, but not more than > > half, I can live with that. (It cost less than 1/3 the price of the > > original.) > > > > If you keep the same voltage-to-frequency ratio and maximum current the motor > will be happy. > But of course the speed will be lower. For example, if it is designed for > 380V, 240Hz, 14,400RPM, > the volts-per-hertz ratio is 380/244 = 1.5833. If the VFD can only deliver > 208V, then you will be > limited to 208/1.5833 = 131Hz, and the top speed will be 7860 RPM. It will > still deliver rated torque > at rated current, but since the speed is lower the kW will be lower - only > about 3.8kW. > > You can run it at a lower voltage-to-frequency ratio, but you won't get the > same torque. For example > you could run it at 208V and 240Hz. You would get a no-load speed of > 14,400RPM, but the torque- > per-amp will be lower - you'll still only get 3.8kW. > > > -- > John Kasunich > jmkasun...@fastmail.fm I agree. To keep voltage-to-frequency ratio up to the maximum voltage and then just increase frequency is probably the best. The VFD may use space vector control instead of voltage-to-frequency ratio. Did you double check if your motor is Delta connected and may be Y connected instead? Nicklas Karlsson -- ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users -- ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Spindle Voltage?
On 11/03/2015 10:16 AM, Karlsson & Wang wrote: >> >> I have been running a 480 V motor at 240 V for a while now on a manual >> mill. At half the voltage you get one fourth the power. >> >> Ed. > A half voltage and same speed you get half power. At half speed and half > voltage you however get one fourth the power. > > I went right over the VFD part, was thinking line volts and line Hz. Ed. -- ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Spindle Voltage?
Trickier than that. Depending on the corner point it may be able to develop the same hp at half speed w/ twice the torque. One would think that an induction motor that needed variable speed would be designed to top out somewhere on the const hp part of the curve than right on the corner point. Induction motors can naturally field weaken so that can have a 2+:1 const hp regions. FWIW, permanent magnet machines can do the same but there are two 'gotchas' to be careful with. 1) Too much field weakening can demagnetize the magnets limiting the useful range and 2) if there is a fault and you have to turn the drive off while in this mode, the field weakening will also disappear and the back EMF will jump suddenly, rectify back through the bridge, and make the bus voltage jump (possibly by a factor of 2+!). You may need a way to mechanically disconnect the motor from the bridge in a fault to protect the vfd from overvoltage. Been there, done that, have the t-shirt! Another thing to note. Space Vector Modulation (SVM) is a bridge modulation scheme - a type of PWM. Can be used in V/Hz drives or flux vector drives which are both control methods. They are not directly related. You can have a V/Hz control using SVM or a flux vector control using something like hysteresis modulation. SVM is typically the superior modulation (most efficient). (neglecting state space control) SMD On Tue, Nov 3, 2015 at 2:12 PM, Przemek Klosowski < przemek.klosow...@gmail.com> wrote: > On Tue, Nov 3, 2015 at 10:02 AM, John Kasunich> wrote: > > > But of course the speed will be lower. For example, if it is designed > for > > 380V, 240Hz, 14,400RPM, > > the volts-per-hertz ratio is 380/244 = 1.5833. If the VFD can only > > deliver 208V, then you will be > > limited to 208/1.5833 = 131Hz, and the top speed will be 7860 RPM. It > > will still deliver rated torque > > at rated current, but since the speed is lower the kW will be lower - > only > > about 3.8kW. > > > > It's not my specialty so I am trying to go over the numbers > methodically---please check if I am getting it right. > At nominal 380V the thing runs at 6kW6kW * 208/380 and 60*240 Hz, i.e. > 14400 rpm. At 208V it should do 208/380*14400, or 7880 rpm, close enough. > But for power, P=omega*T, 6kW * 208/380, or 3.28 kW. amirite? > > -- > ___ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > -- ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
[Emc-users] Spindle Voltage?
I recently purchased an inexpensive router spindle off of ebay. It is rated at 6kw and 380v 3ph. The old spindle I'm replacing was dual voltage and could be wired Y or delta, for 200-240 or 380-460 (7HP). Stupid me I didn't think to check the old VFD and it is only capible of low voltage (running 208 3ph). So my question, what are the repercussions of feeding this motor with only 208 3ph? If the only problem is a loss of a percentage of power, but not more than half, I can live with that. (It cost less than 1/3 the price of the original.) -- Todd Zuercher mailto:zuerc...@embarqmail.com -- ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Spindle Voltage?
On 11/03/2015 08:41 AM, Todd Zuercher wrote: > I recently purchased an inexpensive router spindle off of ebay. It is rated > at 6kw and 380v 3ph. The old spindle I'm replacing was dual voltage and could > be wired Y or delta, for 200-240 or 380-460 (7HP). Stupid me I didn't think > to check the old VFD and it is only capible of low voltage (running 208 3ph). > > So my question, what are the repercussions of feeding this motor with only > 208 3ph? > > If the only problem is a loss of a percentage of power, but not more than > half, I can live with that. (It cost less than 1/3 the price of the original.) > I have been running a 480 V motor at 240 V for a while now on a manual mill. At half the voltage you get one fourth the power. Ed. -- ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Spindle Voltage?
> On Tue, Nov 3, 2015, at 09:41 AM, Todd Zuercher wrote: > > I recently purchased an inexpensive router spindle off of ebay. It is rated > > at 6kw and 380v 3ph. The old spindle I'm replacing was dual voltage and > > could be wired Y or delta, for 200-240 or 380-460 (7HP). Stupid me I didn't > > think to check the old VFD and it is only capible of low voltage (running > > 208 3ph). > > > > So my question, what are the repercussions of feeding this motor with only > > 208 3ph? > > > > If the only problem is a loss of a percentage of power, but not more than > > half, I can live with that. (It cost less than 1/3 the price of the > > original.) > > > > If you keep the same voltage-to-frequency ratio and maximum current the motor > will be happy. > But of course the speed will be lower. For example, if it is designed for > 380V, 240Hz, 14,400RPM, > the volts-per-hertz ratio is 380/244 = 1.5833. If the VFD can only deliver > 208V, then you will be > limited to 208/1.5833 = 131Hz, and the top speed will be 7860 RPM. It will > still deliver rated torque > at rated current, but since the speed is lower the kW will be lower - only > about 3.8kW. > > You can run it at a lower voltage-to-frequency ratio, but you won't get the > same torque. For example > you could run it at 208V and 240Hz. You would get a no-load speed of > 14,400RPM, but the torque- > per-amp will be lower - you'll still only get 3.8kW. > > > -- > John Kasunich > jmkasun...@fastmail.fm I agree. To keep voltage-to-frequency ratio up to the maximum voltage and then just increase frequency is probably the best. The VFD may use space vector control instead of voltage-to-frequency ratio. Did you double check if your motor is Delta connected and may be Y connected instead? Nicklas Karlsson -- ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
Re: [Emc-users] Spindle Voltage?
On Tue, 03 Nov 2015 08:54:32 -0600 Edwrote: > On 11/03/2015 08:41 AM, Todd Zuercher wrote: > > I recently purchased an inexpensive router spindle off of ebay. It is rated > > at 6kw and 380v 3ph. The old spindle I'm replacing was dual voltage and > > could be wired Y or delta, for 200-240 or 380-460 (7HP). Stupid me I didn't > > think to check the old VFD and it is only capible of low voltage (running > > 208 3ph). > > > > So my question, what are the repercussions of feeding this motor with only > > 208 3ph? > > > > If the only problem is a loss of a percentage of power, but not more than > > half, I can live with that. (It cost less than 1/3 the price of the > > original.) > > > I have been running a 480 V motor at 240 V for a while now on a manual > mill. At half the voltage you get one fourth the power. > > Ed. A half voltage and same speed you get half power. At half speed and half voltage you however get one fourth the power. -- ___ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users