RE: [CAD_CAM_EDM_DRO] Re: Servo motor voltage

I think you may need more than 66V.
Ldi/dt+Ri+Ke*kRPM=(small if controlled)+4*8.9+25*2.100=88.1V
(Ldi/dt) should be small if controlled because i is proportionate to Torque and you can control
the rate of change of torque. Also L tends to be small...

If the speed is 0 and the max current is used, then the voltage is 4*44.5=178V (momentarily)

Your estimates may be too high, or you may want a higher voltage power supply (and servo amp with higher rating)or a combination of the two.


-----Original Message-----
From: Chris Baugher [mailto:cbaugher_yahoo@...]
Sent: Tuesday, April 01, 2003 1:26 AM
To: CAD_CAM_EDM_DRO@yahoogroups.com
Subject: Re: [CAD_CAM_EDM_DRO] Re: Servo motor voltage



Hmm, I guess I'm not sure where you got the 48V from. 48V was for the
transformers I'm looking at. Anyway, here are the motor specs I have:

3 Electro-Craft DC Brushed Servo Motors, Model E712

37.51 Oz-In/A
25.0-30.5 V/KRpm
Motor Terminal Resistance .75-1.02 Ohms @ 4A.
Maximum Terminal Voltage 60V
Maximum Continuous Speed 2100 RPM (No Load)
Maximum Peak Torque 1500 Oz-In.
Maximum Peak Current 44.5A (I think - the scan I have is very blurry)
Maximum Continuous Stall Torque At Max Motor Temp 300 Oz-In.
Maximum Continuous Current 8.9A

So what I want to know is if a 66V supply will be ok for these motors.

C|

On Tue, 1 Apr 2003, Mariss Freimanis wrote:
> Chris,
>
> The motor has a rated RPM at 48VDC, at 66V its RPM will be 66/48 or
> 1.375 times higher. The motor's rated power is its rated continuous
> torque times RPM. At 66V it will produce 1.375 times more power than
> its rating. I just don't think that is a good idea for long life
> reliability.
>
> Mariss
>
> --- In CAD_CAM_EDM_DRO@yahoogroups.com, Chris Baugher
> <cbaugher_yahoo@b...> wrote:
> > On Tue, 1 Apr 2003, Mariss Freimanis wrote:
> >
> > > Chris,
> > >
> > > If you don't ask the motor to go faster than its rated speed at
> 48VDC
> >
> > Ok, well the max speed is 2100 RPM and the max voltage is 60V. So I
> > should limit the motor speed to ~1700 RPM? What's the reasoning
> behind
> > that?(I'm not doubting you I'm just curious)
> >
> > > and if you don't load the motor past its rated torque then your
> 66VDC
> > > should be just fine.
> > > The 5V stuff makes it impossible to overload the motor; in your
> case
> > > you'll have to take care not to.
> >
> > That makes sense.
> >
> > C|
>
>
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