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I am aware that chopper drivers for stepper motors need to be supplied with a voltage much higher than the motor's steady state voltage. For instance most 3D printers use drivers based on chips such as the A4988, which is commonly supplied with 12 V, while the motors are rated for only a few volts. See example motor and driver; the common RepRap 3D printers mostly run on 12 V.

My question is as follows: Why stop at 12 V?

As of my understanding, a higher voltage allows for a faster current rise, and hence better torque at higher speeds. So why not increasing the supply voltage to 18 V, or 24 V, which is still within the specs of the driver?

I can only guess at the possible drawbacks. Efficiency of the driver? Safety? Cost of the peripheral electronics (e.g. caps)? Noise?

Note that my question is not limited to the above mentioned hardware; I am interested in the general limits to driving stepper motors with higher voltages of, say, 24 V.

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  • \$\begingroup\$ I think you might be asking too much of the motor so if you want this resolved, provide a link to a typical low voltage stepper motor. \$\endgroup\$
    – Andy aka
    Dec 13, 2015 at 12:48
  • \$\begingroup\$ I was interested in the general problem, rather than for a specific motor. How could a higher voltage (but the same average current) over-stress the motor? \$\endgroup\$
    – polwel
    Dec 13, 2015 at 13:41
  • \$\begingroup\$ You can establish the general validity of your observations by providing a link to a motor. Without a good example you are restricting the number of people who can provide an answer. Do you want that? \$\endgroup\$
    – Andy aka
    Dec 13, 2015 at 14:53
  • \$\begingroup\$ Ok, just added an example. I am new to Stackexchange, so I appreciate your help :) Note though that I do not own the particular motor I listed above, it just serves as an illustration. \$\endgroup\$
    – polwel
    Dec 13, 2015 at 15:38
  • \$\begingroup\$ It's about dielectric strength of widings and max. permissible voltage of the driver. I do normaly use steppers rated for 325V, but they are quite powerful compared to reprap. \$\endgroup\$ Dec 13, 2015 at 16:56

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Don't be confused with voltage ratings described by resellers that they don't know what they are selling. For example the voltage rating for the motor you attached in link is 4V and it turns out that rated current 1.2A and rated resitance 3.3ohm needs those 4V (1.2 * 3.3 = 3.96V), but this voltage is needed at standstill, therefore no moving. When motor spins it produces back EMF and the voltage applied has to be greater in order to feed the motor with current. The real maximum operating voltage is indeed limited by the withstanding dielecric strength of insulating material.
Stepper motor driver is a current source and feeds the motor with constant current, the voltage is variable, rough formula V_driver = V_backEMF + R_wire * I_rated. V_backEMF = K[V/rpm] * N[rpm], not always the sellers know or share the most important parameter - K[V/rpm].
When decelerating, the motor turns into a generator mode and dumps the energy back into the caps. If caps have enough capacitance then the voltage rise is small, but if you have small caps then voltage can rise above max. permissible voltage that your driver can handle.

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  • \$\begingroup\$ Thanks for your answer, I appreciate your effort. I know that the driver is essentially a constant current source, and that the resistance of the winding is not really meaningful (hence why I was reluctant to post a link to an example). How would a larger supply voltage be related to the energy generated during the non-driven period? \$\endgroup\$
    – polwel
    Dec 13, 2015 at 20:34
  • \$\begingroup\$ If by energy you mean heating loss of the driver, then the answer would be specific to the product. \$\endgroup\$ Dec 13, 2015 at 21:15

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