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sandman2234
06-01-2004, 10:08 PM
Having acquired several servo motors lately, I am wondering how to determine what "horsepower" they are. Probably rated in increments of torque, but I have no idea how to determine it.
The last one I got was 400w with a No backlash 15:1 gearbox. The other 2 are like this...
http://img58.photobucket.com/albums/v177/sandman2234/servospecs4.jpg

Anybody have any idea?
David from jax

Bruce Griffing
06-01-2004, 10:26 PM
If the motor is 100% efficient then 746 watts is one horsepower. I don't have a clue as to the efficiency of servo motors.

CCWKen
06-01-2004, 11:14 PM
If you use the watt conversion, the motor in the pic (500watt) is about .67 HP. Bear in mind the torque on that motor is only 1.17 ft/lbs (14 in/lbs, 1.59Nm). Without a gearbox, it may make a good fan motor.

If you use the torque-rpm formula, the motor is only .056HP.

06-02-2004, 12:33 AM
Axis motion designers are more concerned with torque than HP beacuse they know the mass of the moving elements, the friction of the moving parts, and the intervening reduction to match the motor to the steady state load and the desired accelleration. From this they select a motor having X torue to drive it and a capability of Y RPM to attain the required axis velocity.

HP at a given torque increases with linearly with the motor's RPM but this cannot be endlessly extrapolated in real life.

Calculating mechanical HP from electrcial input is a shot in the dark without dyno tests. If you can track down the torque specs, V/hz, thermal dissipation curves, etc of your motors via customer service at Yaskawa or whoever you stand a better chance of getting the best perfrance from your servos.

Chances are someplace in the servo is a thermal sensor normally connected to the fault string of the control. Take advantage of it and your motors will never fry.

You can work out HP from:

HP = T x RPM / 5252

[This message has been edited by Forrest Addy (edited 06-02-2004).]

Bruce Griffing
06-02-2004, 07:43 AM
If the HP of this motor is calculated on the basis of torque and RPM using the nameplate numbers of 1.17 and 3000 it comes to 0.65hp very close to the HP calculated on the basis of electrical power. The output torque after the gearbox would be about 17.5 foot pounds.

sandman2234
06-02-2004, 06:59 PM
If it matters, the drives for these say 200v.
http://img58.photobucket.com/albums/v177/sandman2234/servodrives.jpg

The more I understand, the more confused I get.
David from jax