[Viriality]

Hey, and thank you so much for your time!

The Motor is the kollmorgen akm2g-31PL model (for 48 VDC)

The motor will drive a linear actuator to lift a prop 1 foot.

The calculated thrust is 428.5N,
Torque required (with safety factor 1.3) is 3.02Nm
Speed Required is 2160rpm
Max Acceleration: 1.3716m/sec^2

How to find what current it'll draw, or what output the servo drive will need in order to meet the mechanical requirements?

It's the only blip in the road I can't seem to figure out - I'm confused at all of the motor parameters and which is relevant, if they're straight calculations or if conversions are required.

[Jim Dawson]

The relevant data is the drive specifications. You need to look at the max rated power input data for the mating drive.

A quick look at the Kollmorgen site indicates the motor that you are specifying might be a bit light for the job. Looks like you need akm2g-32PL at a minimum to meet your torque requirement.

https://www.kollmorgen.com/en-us/products/motors/servo/akm-series/akm2g/akm2g-servo-motor/

[joeavaerage]

Hi,
there is a parameter that is almost always published in the specs is the current/torque constant. Typically 0.84A/Nm....or a figure like that.

If you know the torque required for acceleration plus thrust plus drag then you have a vey good estimate of the current.

Craig

[mactec54]

Hi,
there is a parameter that is almost always published in the specs is the current/torque constant. Typically 0.84A/Nm....or a figure like that.

If you know the torque required for acceleration plus thrust plus drag then you have a vey good estimate of the current.

Craig

That has nothing to do with the servo drive current draw requirements, most manufacturers use the inrush current requirement to determine the Breaker size, which is normally in their specs, or some use the max rated amps of the drive plus 125% to determine the Breaker size

[Viriality]

Thanks all, for taking the time to reply!

So... Say the motor is spec'd to have a continuous current of 20 amps.

Is it always going to draw this current when it runs, regardless of the speed or load it's under?

Taken from the kollmorgen akm2g low voltage selection guide:

They list continuous/max current/torque as being across the board, but -

The motor is spec'd to have a 24vdc, 48vdc, 72vdc, and 96vdc profile.
But I'm confused at how these three relate to the other specs (they list values for each voltage profile):
rated torque(speed)
rated speed
rated power(speed)

So it looks like there is just an increase in speed vs the voltage profile?

Is the continuous current for each voltage profile going to be 20amps?

[Jim Dawson]

Speed is normally related directly to voltage, the higher the voltage, the higher the available speed within the motor rated speed range.

Torque is normally directly related to current (within the rated motor speed range) The current value is the maximum continuous current rating. There should be another current/torque rating that is a maximum intermittent rating, normally 2 to 3 times the maximum continuous rating. The motor will only draw enough power to get the job done. When the move has completed, the motor power draw will be near zero, and will only apply just enough torque to keep the load stationary.

For determining input power to the drive, you need to look at the drive specifications. There will be a maximum input current spec.

[mactec54]

Thanks all, for taking the time to reply!

So... Say the motor is spec'd to have a continuous current of 20 amps.

Is it always going to draw this current when it runs, regardless of the speed or load it's under?

Taken from the kollmorgen akm2g low voltage selection guide:

They list continuous/max current/torque as being across the board, but -

The motor is spec'd to have a 24vdc, 48vdc, 72vdc, and 96vdc profile.
But I'm confused at how these three relate to the other specs (they list values for each voltage profile):
rated torque(speed)
rated speed
rated power(speed)

So it looks like there is just an increase in speed vs the voltage profile?

Is the continuous current for each voltage profile going to be 20amps?

The max current no, it is not always going to draw the max continuous current, but the Breaker has to be rated for this,20A X 125%=25A this gives you the Breaker size, the inrush current when you start the servo is normally 2 to 3 x the rated current, which ends up being close to the same as the max continuous current.