Re: [CAD_CAM_EDM_DRO] Transformer sizing
Posted by
Jon Elson
on 2004-01-13 08:52:46 UTC
bolttjza wrote:
Figuring the desired linear force on the table back through the ballscrew
and belt drive, you can figure out the torque you need, and then the
drive ratio that is most appropriate. Then, check the top rapid feed rate
you want, and make sure the motor speed at 100 V will reach that.
Sounds like you'll be using Rutex drives?
Note that these motors are really strong, if you apply 26 A it may break
belts even 3/4" wide! So, check the specs on the belts you plan to use
to make sure you stay within their ratings. Keep in mind that these
belts need to be kept REAL tight to prevent creep, and add the tension
to the motor force.
As for the transformer, it is very unlikely you will ever run 100 V and
20 A through the motor at the same time, except for a very short instant
when accelerating. But, when all 3 motors are accelerating at the same
time, the power draw will be substatial. Note that PWM servo drives
are switching power supplies, and so power in roughly equals power out.
So, if the drive is delivering 20 A at 5 V out, it will only need 100 W
at the input (plus losses) and so will only draw 1 A from the power supply!
A 1 KVA transformer soulds like a good minimum. You could
probably go to 1.5 or even 2 KVA. There is no reason to go above
that, however, for a milling machine. Even though the theoretical
power draw could be 6 KVA (100V x 20A x 3 axes) you just never
do that except for instantaneous surges . Make sure there is plenty
of filter capacitor for energy storage, and that the rectifiers are
sufficient. I might go with 50 A diodes for this.
Jon
>Hi All,First, you need to get the torque/Amp constant (Kt) for your motor.
>
>I need some help in sizing a power supply for a Bridgeport series
>1/EMC conversion. I will be driving each axis with 140V SEM PMDC
>servo motor of which the stall current is 26A. The drive powering
>these motors are capable of supplying 100V @ 20A. I will drive a 5mm
>pitch ball screw thourgh 2:1 reduction ratio. What VA transformer
>should I purchase? Am I ever likley to use 100V @ 20A? Should the
>reduction ratio be bigger ie 3:1 or 4:1?
>
>
Figuring the desired linear force on the table back through the ballscrew
and belt drive, you can figure out the torque you need, and then the
drive ratio that is most appropriate. Then, check the top rapid feed rate
you want, and make sure the motor speed at 100 V will reach that.
Sounds like you'll be using Rutex drives?
Note that these motors are really strong, if you apply 26 A it may break
belts even 3/4" wide! So, check the specs on the belts you plan to use
to make sure you stay within their ratings. Keep in mind that these
belts need to be kept REAL tight to prevent creep, and add the tension
to the motor force.
As for the transformer, it is very unlikely you will ever run 100 V and
20 A through the motor at the same time, except for a very short instant
when accelerating. But, when all 3 motors are accelerating at the same
time, the power draw will be substatial. Note that PWM servo drives
are switching power supplies, and so power in roughly equals power out.
So, if the drive is delivering 20 A at 5 V out, it will only need 100 W
at the input (plus losses) and so will only draw 1 A from the power supply!
A 1 KVA transformer soulds like a good minimum. You could
probably go to 1.5 or even 2 KVA. There is no reason to go above
that, however, for a milling machine. Even though the theoretical
power draw could be 6 KVA (100V x 20A x 3 axes) you just never
do that except for instantaneous surges . Make sure there is plenty
of filter capacitor for energy storage, and that the rectifiers are
sufficient. I might go with 50 A diodes for this.
Jon
Discussion Thread
bolttjza
2004-01-13 06:50:56 UTC
Transformer sizing
Jon Elson
2004-01-13 08:52:46 UTC
Re: [CAD_CAM_EDM_DRO] Transformer sizing
Robb Greathouse
2004-01-13 12:25:42 UTC
Lasers - its the cheese
bolttjza
2004-01-14 03:20:47 UTC
Re: Transformer sizing