Re: rpc *data*--under resistive load ! .... Re: Balancing rpc's. A+ replies.
- From: "DrollTroll" <fitcat@xxxxxxxxxxxxx>
- Date: Fri, 8 Aug 2008 04:49:38 -0400
"Denis G." <guillemd@xxxxxxx> wrote in message
news:0ca30cd1-05cf-4ab8-8c1a-bb4beceb87e4@xxxxxxxxxxxxxxxxxxxxxxxxxxxxxx
I looked at your data, but?.
Resistive loads and reactive loads act differently in AC circuits.
http://en.wikipedia.org/wiki/Load_bank
Resistive circuits don?t cause phase shifts. That?s the problem in
trying to using resistors as a substitute for your induction motor.
In this type of circuit with a motor, you HAVE phase shifts and the
process of tuning is to try and minimize them by adjusting
capacitance. It?s just the nature of the beast.
You can adjust a resistive load to make it draw the same as a motor,
but it will only be a good substitute for a motor circuit with a PF=1.
It won?t be a good substitute for your motor and it won?t help you to
tune your RPC.
With reactive loads (such as motors), you get phase shifts between the
current and voltage curves (PF<1) and when you tune the circuit by
adding capacitance to balance the phase shift caused by inductance in
the motor. In essence, you try to shift the voltage and current
curves back together and get as close to PF=1 as possible. This
optimizes power transfer to the motor.
I know that you are just trying to get this thing to work and all this
probably sounds like ?hand waving?, but you are better off trying to
balance your RPC with your real-live motor in place and under some
mechanical load.
I hope that you get your project working, and my apologies if this was
not helpful or I?ve erred.
=============================================
Well, I can do exactly the same thing using a 5 hp motor as the load.
Maybe your point that pure resistive loads don't cause phase shifts is why I
never had to change the capacitance value!
As you pointed out earlier, it would not be a motor under load, unless it
were, well, loaded!
Your pump idea would be very good, if I had one, or even a compressor head.
Or an auxiliary generator head.
Or mebbe just find a motor with really bad bearings!!
Actually, I do have one possible solution:
A kalamazoo hydraulic cutoff saw, while cutting. The hydraulic motor should
be a constant load (for the hydraulic vise), and the blade motor, while
cutting a thick material, should offer a pretty constant load, as well.
RPC's can be tuned only approximately anyway (iiuc), as what is right for a
given motor under one load won't be quite right for that same motor under
another load. Or other motors. Correct?
So you sort of have to anticipate a load in advance, for optimal tuning.
I'll keep an eye out for some kind of generator head. That would be a very
cool way of doing this, as a resistive load (and the current thereof) on a
generator is accurately measurable and reproducible.
--
DT
.
- References:
- Balancing rpc's.
- From: DrollTroll
- Re: Balancing rpc's. A+ replies.
- From: spaco
- rpc *data*--under resistive load ! .... Re: Balancing rpc's. A+ replies.
- From: DrollTroll
- Re: rpc *data*--under resistive load ! .... Re: Balancing rpc's. A+ replies.
- From: Denis G.
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