Stepper Motor as generator : How efficient is it?
My engines 4:03
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In this video I show you how to measure the efficiency of a stepper motor as a generator using a prony brake.
I compare the mechanical input power with the electrical output power to find out if the use of a stepper motor as a generator makes sense.
If you want to support me and become a channel member you get access to exclusive content in the members area:
https://www.youtube.com/channel/UCie-_1q_BTL_cpPN_6f0gHw/join
Thanks to Baptiste (alias OfficialyMax) we now have a Discord server:
https://discord.com/invite/TDABS5z2mT
It would be very nice if we could discuss there everything about Stirling engines, 3D printing and more, thank you very much Baptiste.
A stepper motor would be the ideal generator for my thermoacoustic Stirling engine.
Even at low speeds, a stepper motor supplies high voltages and has a high torque for starting the Stirling.
I couldn't find any reliable information about the efficiency of a stepper motor in generator mode.So, I built a test rig in order to measure the efficiency precisely.I have already used linear, DC and brushless DC generators for the power utilisation of my Stirling engines.A stepper motor offers many advantages.It delivers high voltages even at low speeds, can easily be controlled to start the Stirling, and has high torque.
It is also available in many sizes and types at a favourable price.
But can its efficiency in generator mode keep up with DC or brushless DC motors?A stepper motor is designed for powerful and precise positioning tasks and not for maximum energy efficiency.
As I couldn't find any reliable information about the efficiency of a stepper motor in generator mode anywhere, I decided to build a test rig myself.
I use a Prony brake to measure the drive torque.
A 100 mm long lever is attached to the rotating drive motor and presses on a scale.The resulting torque together with the measured rotational frequency gives the mechanical input power.The electrical output power of the stepper motor from the product of the rectified, smoothed voltage and current divided by the mechanical input power then gives the generator efficiency of the stepper motor.To rectify the generated alternating current, I use two normal bridge rectifiers which reduce the efficiency, especially at low voltages, but the influence should not be too great at higher rotation frequencies.I have already ordered ideal or active diodes for use as rectifiers in order to obtain more precise results and to avoid wasting energy when using the Stirling engine to generate electricity.
The output voltage and current naturally pulsate slightly, but a check with the oscilloscope shows that this influence is almost negligible.
Years ago I measured the very high-quality Maxon DC drive motor.
Depending on the operating point, it has an efficiency of up to 0.75 as a generator.The cheap Nema 17 stepper motor tested here from my old Ender 3 3D printer has so far delivered efficiencies of up to 0.65 at over 15 volts.
I haven't even looked for the optimum operating point, tried only a few different electrical loads and haven't gone above 1000 rpm.
I measure the stepper motor more extensively, which I later use as a generator in the Stirling engine.I am very satisfied with these results and amazed at how good the efficiency of the cheap Nema 17 stepper motor is even with these first measurements.I now believe that a stepper motor can be a good generator, at least for the development phase, which in addition to a reasonable efficiency also has important advantages for me such as easy controllability, high torque and high voltage with only oscillating rotary motion.For the final productive continuous operation to support the solar plant, however, a generator specially optimised for maximum efficiency is probably more suitable.
Do you have any suggestions, ideas or criticism?
As always, I look forward to your comments here on YouTube or Discord!
Many thanks for watching!
Thanks for the background music:
Song: Jim Yosef - Eclipse [NCS Release]
Music provided by NoCopyrightSounds
Free Download/Stream: http://ncs.io/eclispe
Watch: • Jim Yosef - Eclipse | House | NCS
I compare the mechanical input power with the electrical output power to find out if the use of a stepper motor as a generator makes sense.
If you want to support me and become a channel member you get access to exclusive content in the members area:
https://www.youtube.com/channel/UCie-_1q_BTL_cpPN_6f0gHw/join
Thanks to Baptiste (alias OfficialyMax) we now have a Discord server:
https://discord.com/invite/TDABS5z2mT
It would be very nice if we could discuss there everything about Stirling engines, 3D printing and more, thank you very much Baptiste.
A stepper motor would be the ideal generator for my thermoacoustic Stirling engine.
Even at low speeds, a stepper motor supplies high voltages and has a high torque for starting the Stirling.
I couldn't find any reliable information about the efficiency of a stepper motor in generator mode.So, I built a test rig in order to measure the efficiency precisely.I have already used linear, DC and brushless DC generators for the power utilisation of my Stirling engines.A stepper motor offers many advantages.It delivers high voltages even at low speeds, can easily be controlled to start the Stirling, and has high torque.
It is also available in many sizes and types at a favourable price.
But can its efficiency in generator mode keep up with DC or brushless DC motors?A stepper motor is designed for powerful and precise positioning tasks and not for maximum energy efficiency.
As I couldn't find any reliable information about the efficiency of a stepper motor in generator mode anywhere, I decided to build a test rig myself.
I use a Prony brake to measure the drive torque.
A 100 mm long lever is attached to the rotating drive motor and presses on a scale.The resulting torque together with the measured rotational frequency gives the mechanical input power.The electrical output power of the stepper motor from the product of the rectified, smoothed voltage and current divided by the mechanical input power then gives the generator efficiency of the stepper motor.To rectify the generated alternating current, I use two normal bridge rectifiers which reduce the efficiency, especially at low voltages, but the influence should not be too great at higher rotation frequencies.I have already ordered ideal or active diodes for use as rectifiers in order to obtain more precise results and to avoid wasting energy when using the Stirling engine to generate electricity.
The output voltage and current naturally pulsate slightly, but a check with the oscilloscope shows that this influence is almost negligible.
Years ago I measured the very high-quality Maxon DC drive motor.
Depending on the operating point, it has an efficiency of up to 0.75 as a generator.The cheap Nema 17 stepper motor tested here from my old Ender 3 3D printer has so far delivered efficiencies of up to 0.65 at over 15 volts.
I haven't even looked for the optimum operating point, tried only a few different electrical loads and haven't gone above 1000 rpm.
I measure the stepper motor more extensively, which I later use as a generator in the Stirling engine.I am very satisfied with these results and amazed at how good the efficiency of the cheap Nema 17 stepper motor is even with these first measurements.I now believe that a stepper motor can be a good generator, at least for the development phase, which in addition to a reasonable efficiency also has important advantages for me such as easy controllability, high torque and high voltage with only oscillating rotary motion.For the final productive continuous operation to support the solar plant, however, a generator specially optimised for maximum efficiency is probably more suitable.
Do you have any suggestions, ideas or criticism?
As always, I look forward to your comments here on YouTube or Discord!
Many thanks for watching!
Thanks for the background music:
Song: Jim Yosef - Eclipse [NCS Release]
Music provided by NoCopyrightSounds
Free Download/Stream: http://ncs.io/eclispe
Watch: • Jim Yosef - Eclipse | House | NCS
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