Re: [CAD_CAM_EDM_DRO] Re: servo voltage question ( regarding Steppers)

You didn't quite answer my question, let me rephrase it.
Suppose I had a 1000 volt power supply and a drive capable
of handling it. Would that destroy a stepper motor?
What would be the actual failure point; insulation, iron
heating, copper heating, some other failure mode.

Given a servo drive setup, what would be the failure mode?

What I am trying understand is what are the absolute voltage
limits on stepper and servo motors.

I understand that Mariss recommends 25 times the motor rating
for stepper motors. That matches well with my 3 volt steppers
and my 70 volt supply.

I do understand that the higher voltage causes the current
to rise faster in the motor windings thereby putting more power
into the motor resulting in getting more power out. If 25 times
is good then 50 times should be better. Where is the limit
from the motors point of view assuming that the drive and
power supply are available.

Pete.

----- Original Message -----
From: "turbulatordude" <dave_mucha@...>
To: <CAD_CAM_EDM_DRO@yahoogroups.com>
Sent: Saturday, January 29, 2005 10:43 AM
Subject: [CAD_CAM_EDM_DRO] Re: servo voltage question ( regarding Steppers)


>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, "Peter Reilley" <micrio@m...>
> wrote:
>> A question on voltage. There must be a maximum voltage that
>> can be applied a motor because of insulation breakdown.
>> For a 4 volt stepper motor what voltage would be too high?
>> What is the voltage rating of the insulation on the wire used
>> in the average stepper motor? Are 30 year old stepper motors
>> going to be significantly worse than new motors? Is there
>> a voltage limit for the brush assembly used in servo motors?
>>
>> Do companies give these ratings? If not what are some good
>> guesses?
>>
>> Pete.
>
>
> The answer lies in the DRIVER MANUFACTURERES literature.
>
> Gecko's are tuned to allow up to 25 times motor nameplate. Other
> manufactureres go much higer, other go lower.
>
> The key to understanding this is in the tutorial to steppers written
> by Jones. Google Jones on Steppers.
>
> Basically, the way I understand it, the amps and ohms and voltage of
> the stepper NAMEPLATE, it for using Ohm's Law for the rest of the
> calculations. This is NOT like your 220VAC motor where Nameplate is
> Maximum.
>
> The namplate offers 1,2 or 3 of these values, you can measure the
> resistance to get that value, so you should be able to get at least 2
> values pretty quickly.
>
> The CHOPPER then pulses the charge into the motor, Volts and Amps,
> until the chopper circuit see enough amps, then it chops the power.
> Since SPEED is the issue, you can dump 10 amps with 100 volts MUCH
> faster than 10 amps with 1 volt.
>
> The motor never sees more than the nameplate current.
>
> As for old steppers VS. new ones, the old round body are different
> than the new square bodies. the new square bodies have
> considderabley higher effiency and have considderably higher power.
>
>
>
> As for SERVO's, like your AC motor, these are charged continually, so
> the motor might have 50 volts on it to hold posistion, like when a
> table is holding against the cutting forces.
>
> And, like transformers, the motor insulation, wire size and spacing
> is all based on voltage and current.
>
> Over voltage and you can break down the insulation and short out the
> windings. Over current and the motor overheats and damage occurs
> there also.
>
> IF (big IF) you can really cool the motor, you can change the
> ratings, but since it is easy to cool the outside case, but not the
> windings on the armature, that feat is hard to accomplish with any
> predictability.
>
> Considder that the motor costs will be a factor your project, and
> project life.
>
> I wrestled with a $35 servo and a $125 gear train of my own design to
> handle the high motor RPM. so... if I found a decent low speed motor
> for less than $155, things get much easier. and considdering my time
> in building the gear reduction.....
>
> Hope this helps somewhat.
>
> Dave
>
>
>
>
>
>
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