I think it is a tad optimistic but broadly correct.
DC converter's power factor.
- Thread starter Chelny
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yep
firing ang ~ ph ang ~ pf
in essence pf is indirectly controlled
need more power? increase pf
as you pointed out earlier P = T w (where w = 2 Pi n)
if the load resists a speed increase Z drops and i increases, and therefore T
motor overcomes load and speeds up increasing power
it is an amazing dynamic
firing ang ~ ph ang ~ pf
in essence pf is indirectly controlled
need more power? increase pf
as you pointed out earlier P = T w (where w = 2 Pi n)
if the load resists a speed increase Z drops and i increases, and therefore T
motor overcomes load and speeds up increasing power
it is an amazing dynamic
Actually increasing V does it.
Increasing Va increases Ia
The proportionality is between torque and Ia.
that is what I said
Z decreases, i increases, as does torque
i = V / Z
so if Z decreases, i increases
V constant at a given speed
if the load resists a speed increase Z drops and i increases, and therefore T
exactly correct
according to the drive mfg (Siemens)
at 0 pf must be 0, no work (P x t) being done
and firing ang~pf is linear with speed for a DC set-up
My posts are still being deleted it would seem. Why?
Z is not applicable to DC motors.
BEMF changes with RPM. What changes current, thus torque, is the difference between applied voltage, Va, and BEMF
a DC motor has no inductance or resistance?
exactly what I said
the controller applies a fixed armature V
since Z decreases as motor approaches a stall load>T
Z will decrease, i will increase, as will T
For variable speed DC. The armature voltage is not fixed. It varies more or less proportionate with speed.
Z = ωL -1/jωC
There is no ω with DC.
I wish to discontinue this discussion.
incorrect
seperately excited, field current controls speed
there is relative motion resulting in w
http://pemclab.cn.nctu.edu.tw/W3lib/books/ElectroCraft85/ch2.dcmotor.pdfp
in this case Z = R + jX
X = wL
do so then
Yes, above base speed. Armature voltage controls it up to base speed.
And some don't run above base speed.
???
uh no
perhaps instead of attempting to lecture and correct folks responding to the op, YOU actually answer the op's query?
his question: pf?
he gives the model and manual link
give it a shot
I did answer that point.
We're doe here.
OP
you might find this interesting
http://dranetz.com/wp-content/uploa...correction-harmonic-control-dc-driveloads.pdf
you might find this interesting
http://dranetz.com/wp-content/uploa...correction-harmonic-control-dc-driveloads.pdf
what is the number?
hello guys,
I will look at this pdf.
I see you are still not tired of that.
Here then perhaps one more question on PF calculation. Please look at attachment.
Chelny
hello guys,
I will look at this pdf.
I see you are still not tired of that.
Here then perhaps one more question on PF calculation. Please look at attachment.
Chelny
assuming the DC motor is the one we have been discussing
need the input power for the AC motor
DC machine
S = 128 kva, pf = 0.85, ang = arccos 0.85 = 31.8 deg
S = P + jQ = 0.85 x 128 + j sin31.8 x 128 = 108.8 + j67.5
need to do the same for the AC
S = ? kva pf = 0.92, ang = arccos 0.92 = 23.1 deg
need S for the AC????
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It clearly shows how power factor varies with speed for a DC motor. Note this AC input power factor that you would expect for a shunt wound separately excited machine which many are.hello guys,
I will look at this pdf.
I see you are still not tired of that.
Here then perhaps one more question on PF calculation. Please look at attachment.
Chelny
There are series wound machines. Typically these are used in traction applications and combustion engine starter motors. High torque at low speed is the main attribute.
I've had a few encounters with them but really my area.
OK.
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