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I want to buy this motor SANYO DENKI 103H7823-1741 for building my CNC

I have found the datasheet over here

in the website that I will buy it from it says

Motor: AC; stepper; 100VAC; step 1,8°; 2.7Nm; 1.34kg; 4A

from what I know the stepper motors work with pulses but using DC voltage, so what does it mean to be rated with 100 VAC ?

EDIT

would it make difference if this motor was rated with DC voltage ? Can I drive this motor with 24V DC(of course using stepper motor driver)?

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  • \$\begingroup\$ I think that is just a way to say it is a bipolar stepper. You have to apply an alternating current to make it spin if you think about it. During each step you apply DC, but you are constantly reversing it as you spin, hence a H-Bridge is used. \$\endgroup\$ Mar 19, 2016 at 14:41
  • \$\begingroup\$ but at the same website tme.eu/en/details/103h5208-5240/electric-motors/sanyo-denki there is other bipolor motor rated with DC voltage instead of AC, which makes a lot of confusion for me \$\endgroup\$ Mar 19, 2016 at 14:43
  • \$\begingroup\$ It's not entirely clear which winding option you are being offered with that motor. As to the general question, the simple-case output of an ideal microstepping driver is in fact two orthogonal AC phases, something other drivers only approximate. There exist stepper motors which can be run synchronously from an AC line (or transformer reduced AC) with a phase shift capacitor for the second winding, but that's not necessarily what you are being offered. For CNC you need a low impedance (typically signified by low rated voltage) winding to get good performance. \$\endgroup\$ Mar 19, 2016 at 16:48
  • \$\begingroup\$ Can you mention an example for a low impedance motor, I mean tell me how low it should be to be considered as low in your opinion \$\endgroup\$ Mar 19, 2016 at 17:46
  • \$\begingroup\$ @MuhammadNour - Try here mechapro.de/pdf/H7823-1710.pdf for instance. The motor is rated for 4 amps total, or 2 amps per winding. Winding resistance is listed as 0.65 amps each. So coil voltage is about 1.3 volts. \$\endgroup\$ Mar 19, 2016 at 21:22

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The motor specification in your second link is very badly wrong. The data sheet provided by the website page is for a 24 volt DC stepper motor, as shown on page 6. However, further down the data sheet a system diagram is shown which suggests the use of an AC to DC power supply with an input of 100 to 240 VAC - that is, just about any AC voltage you'll find in the world. So the description is badly misleading. Why they called it a 100 VAC stepper is impossible to say, but a major brain fart by whoever created the web page is a good bet.

The linked datasheet is correct, and as it states, the nominal operating conditions are 4 amps at 1.4 volts. That is, it's a bipolar stepper with 0.65 ohm windings and a nominal maximum of 2 amps per winding. In order to drive it, you would want a standard bipolar driver with that capability. If you apply 24 volts, unless the power supply is current limited to 2 amps you will burn out the motor.

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  • \$\begingroup\$ Perhaps, perhaps not. Stepper motors are usually manufactured with a wide range of winding options in the same physical housing, and it's not clear which one the product actually being offered for sale will have. There are even motors of this type wound with high impedance for synchronous operation from the AC mains using a capacitor to phase shift one winding. Generally speaking a low voltage winding is preferred for a CNC machine, as it will have a lower inductance and so can achieve decent torque at high step rates wit a moderate driver voltage. \$\endgroup\$ Mar 19, 2016 at 15:48
  • \$\begingroup\$ Even a 24 volt coil would be far too high for something that needs to work against cutting force and rapid from one position to another. Instead, one wants something like a 4v coil, and a chopping current mode driver than can call on the potential of a much higher supply voltage (24v minimum, perhaps 50v or even 75v) to force rated current against the winding inductance when stepping rapidly. \$\endgroup\$ Mar 19, 2016 at 15:56
  • \$\begingroup\$ The specific entry for that particular motor (actually 103H7823-1740) is on page 41 of the datasheet, and the specs match the ones on the web page, except for that 100VAC number. \$\endgroup\$
    – Dave Tweed
    Mar 19, 2016 at 15:57
  • \$\begingroup\$ @Chris Stratton why would a high voltage stepper motor wouldn't be suitable for CNC machine, I imagine the more voltage it can handle the more torque at higher speed it would be able to achieve, right? \$\endgroup\$ Mar 19, 2016 at 20:24
  • \$\begingroup\$ No, the less. To get good high step rate performance, you want a motor rated for a low voltage (when not moving) and then you operate it with a chopping driver than can call on a far, far higher voltage to rapidly drive current against it when moving. If the driver can only use the rated voltage, you'll quickly hit a commutation speed where you simply don't have time to develop a meaningful current when fighting that inductance. The insulation rating of the winding is another matter - the usual nameplate rating is the voltage at which rated current is achieved when a winding is left on. \$\endgroup\$ Mar 19, 2016 at 20:40
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These are voltages of power supply to the stepper driver, not the motor. You should look for stepper+driver characteristics. There are described characteristics for 24VDC and 100VAC driver + motor, that's the reason this data is in datashhet, but it doesn't mean anything. You can use DC or AC driver packs, as long the DC bus voltage doesn't exceed motor withstanding voltage. More voltage, more rpms. You do need a calc of max rpms you need.

I have mounted these motors with use of RTA drivers, I choosed DC drivers and I used the transformer and rectifier + capacitor circuits arround 50VDC (transformer 38VAC/250VA, Capacitor EPCOS B41560A8229M 22mF@63V) and inrush current limit circuit

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  • \$\begingroup\$ thanks you for your answer, it just confusing me because at the same website there is other bipolar motors rated with DC voltage \$\endgroup\$ Mar 19, 2016 at 15:14
  • \$\begingroup\$ Withstand voltage □42(□ 1.65inch):AC500V 50/60Hz for 1 minute, □50(□ 1.97inch)・□56(□ 2.20inch)・□60(□ 2.36inch):AC1000V 50/60Hz for 1 minute: these are important data, as you can see you may buy AC driver that goes direct on mains 230VAC, normaly I do use this type for OEM machines, but you may like more a DC PSU, it makes less noise. What are your max RPMs? Becasue you are looking at motor 75V/kRPM, means if you expect 1000rpms the DC bus voltage supply has to higher that 75V. \$\endgroup\$ Mar 19, 2016 at 15:35
  • \$\begingroup\$ @ChrisStratton What are you talking about? These motors are made for CNC, I have installed lot of them. And yes the withstand voltage are for windings, not PSU - it is copied from manual and it is clear, therefore if it withstands 1000VAC it is suitable to use a driver with AC input 230VAC, or not? \$\endgroup\$ Mar 19, 2016 at 15:49
  • \$\begingroup\$ @MarkoBuršič - the same motor is typically offered with a wide range of windings options, and it is not clear which is being offered. Only the lowest impedance options will be satisfactory in a non-trivial CNC application. You may not be aware of it, but the range of windings for motors of this type can include those with sufficient impedance to be operated from the AC mains with a phase shift capacitor - 100 VAC is entirely plausible. You really can't say if this motor is suitable without knowing exactly which of the winding options it will be delivered with. \$\endgroup\$ Mar 19, 2016 at 15:52
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    \$\begingroup\$ how did you calculate the speed? \$\endgroup\$ Mar 19, 2016 at 18:36

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