[piovanelli]

Hey guys, I received some motors this week, but I'm having some problems with the specifications that came with them. As you can see in the file, their current is 3a/phase. But it doesn't mention if this is a peak or a RMS current. Could you help me? This is a peak or a RMS current?

Thanks!!!

[Al_The_Man]

Bi-Polar stepper motors 3Amps DC.
Al.

[piovanelli]

Bi-Polar stepper motors 3Amps DC.
Al.

So, 3a DC, that means it's a continuous current (RMS)?

[Al_The_Man]

RMS refers to an AC current.
RMS does not apply to pure DC.
Al.

[piovanelli]

RMS refers to an AC current.
RMS does not apply to pure DC.
Al.

So, why it's mentioned in the driver? My drivers can be configured to 3a peak (2,1 rms) or 4.2a peak (3 rms). Which one should I use with those motors, if they are 3a DC, as you mention?

[kreutz]

[quote=Al_The_Man;1113881]Not quite right. The r.m.s. value of a DC current is equal to its peak value (DC level), that's why the r.m.s. value is seldom used when working with DC currents and voltages.

kreutz

[kreutz]

So, why it's mentioned in the driver? My drivers can be configured to 3a peak (2,1 rms) or 4.2a peak (3 rms). Which one should I use with those motors, if they are 3a DC, as you mention?

It depends on the way you drive the motors.

Full Step = Adjust to Peak current Value specified for the motor
Micro-step = Adjust to R.m.s. value

Best regards,

kreutz

[piovanelli]

Not quite right. The r.m.s. value of a DC current is equal to its peak value (DC level), that is why the r.m.s. value is seldom used when working with DC currents and voltages.

Best regards,

kreutz

In the file below are the specifications of a driver to which I must supply 24 - 80 vdc. As you can see, there is a difference between the peak and RMS current. In the case of my motors (3a/phase, that I don't know if its a peak or a rms value), which configuration should I use? 2,8a peak or 4,2a peak? As you can see in the file attached to the first post, the motor specifications don't mention if it's a peak or a RMS, only that it's a 3a/phase motor.

Best regards,

Daniel

[Al_The_Man]

[quote=Al_The_Man;1113881]Not quite right. The r.m.s. value of a DC current is equal to its peak value (DC level), that's why the r.m.s. value is seldom used when working with DC currents and voltages.

kreutz

RMS has always meant to me is the conventional meaning which is the RMS of an AC current is the value of equivalent energy of an AC current to its DC counterpart.
Al.

[kreutz]

[quote=Al_The_Man;1113905]

Not quite right. The r.m.s. value of a DC current is equal to its peak value (DC level), that's why the r.m.s. value is seldom used when working with DC currents and voltages.

kreutz

RMS has always meant to me is the conventional meaning which is the RMS of an AC current is the value of equivalent energy of an AC current to its DC counterpart.
Al.

That is correct. The complete "text book" definition would require to specify "heat energy" and to add "when they are flowing through an equal resistance'" at the end of your definition.

Best regards,

kreutz

[kreutz]

In the file below are the specifications of a driver to which I must supply 24 - 80 vdc. As you can see, there is a difference between the peak and RMS current. In the case of my motors (3a/phase, that I don't know if its a peak or a rms value), which configuration should I use? 2,8a peak or 4,2a peak? As you can see in the file attached to the first post, the motor specifications don't mention if it's a peak or a RMS, only that it's a 3a/phase motor.

Best regards,

Daniel

Motors specify "peak value" because "traditionally" most manufacturers specify the peak value for "Full Step" mode, which is a DC current, as the maximum operating current.

When working with micro-stepping drives, it does make more sense to define the maximum as an r.m.s. value because the micro-stepping current waveform is a "quasi-sinusoidal form" not a dc level. You have to be careful because under 1/8 micro-step (half-step, 1/4 step) the waveform isn't quite sinusoidal so their "crest factor" is not the same and has to be measured before setting a current value for those modes. If you chose to work using peak mode you won't damage the drive (or the motor) but you will get less than the maximum available torque at low speeds.

Best regards,

kreutz

[piovanelli]

Motors specify "peak value" because "traditionally" most manufacturers specify the peak value for "Full Step" mode, which is a DC current, as the maximum operating current.

When working with micro-stepping drives, it does make more sense to define the maximum as an r.m.s. value because the micro-stepping current waveform is a "quasi-sinusoidal form" not a dc level. You have to be careful because under 1/8 micro-step (half-step, 1/4 step) the waveform isn't quite sinusoidal so their "crest factor" is not the same and has to be measured before setting a current value for those modes. If you chose to work using peak mode you won't damage the drive (or the motor) but you will get less than the maximum available torque at low speeds.

Best regards,

kreutz

Kreutz,

This is the site of the company that produces the drivers, with its specifications:

M880A Stepper Drive - Leadshine Technology Co., Ltd.

As you can see, it works with a "Pure-sinusoidal current control technology", and doesn't work in full step, it goes from 400 steps/revolution to 51200 steps/revolution, so, always in microstepping. In that case, should I follow your previous advice? That's not the first time that I have a problem due to this lack of complete information in the specifications of the motor. Considering that the driver works in a pure-sinusoidal waveform, I believe it's important to know if the 3a/phase mentioned in the specs of the motors are related to a peak or a RMS.

Thanks for the help.

Best regards,

Daniel.

[kreutz]

Kreutz,

This is the site of the company that produces the drivers, with its specifications:

M880A Stepper Drive - Leadshine Technology Co., Ltd.

As you can see, it works with a "Pure-sinusoidal current control technology", and doesn't work in full step, it goes from 400 steps/revolution to 51200 steps/revolution, so, always in microstepping. In that case, should I follow your previous advice? That's not the first time that I have a problem due to this lack of complete information in the specifications of the motor. Considering that the driver works in a pure-sinusoidal waveform, I believe it's important to know if the 3a/phase mentioned in the specs of the motors are related to a peak or a RMS.

Thanks for the help.

Best regards,

Daniel.

Hello;

The 3 Amps/phase specified for your motor is the "peak" value. The corresponding r.m.s. value would be 3 / 1.41 = 2.12 Amps.

Best regards,

kreutz