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Hi Mick,
I haven't heard before that inductive motors require reactive power. Unloaded they create inductive reactive power which is compensated by capacitive reactive power. Hector compensates reactive power with the rotoverter.to prevent reactive power in the grid. I haven't seen proof of it self-running as claimed and haven't done experiments with it. It would be interesting if somebody would do the measurements with proper instruments being able to measure the different types of power.
Regards
Ole
---In [email protected], <mkjekyll@...> wrote :
Ole,
OK as usual great description, but I understand all of that and the use of a level reactive power in a transmission line is more efficient from the voltage transmission optimization, however I do not grock the claim concerning the inductive motors requiring > reactive over real and if so why.
On 7/6/2019 8:41 AM, onielsen@... mailto:onielsen@... [EVGRAY] wrote:
Hi Mick,
There are two types of reactive power having different sign (capacitive and inductive power). When they are equal they cancel out each other like in an LC-tank during resonance. The capacitive reactive power then cancels the inductive reactive power leaving only the true or active or real power. During resonance the voltage or current is be increased. At parallel resonance the voltage is increased while the current to/from the LC-tank is decreased. The current between the capacitor and inductor in the tank is also increased during parallel resonance. Only the external current to the tank decreases. Thus having the compensating reactive power close to the device creating the reactive power prevents excess current in the line feeding the device and its reactive power compensation. This makes the line waste less power in resistive heating without increasing the cross sectional area of the wires.
Regards
Ole
---In [email protected] mailto:[email protected], <mkjekyll@...> mailto:mkjekyll@... wrote :
from link
Why Do We Need Reactive Power? Reactive power (VARS) is required to maintain the voltage to deliver active power (watts) through transmission lines. Motor loads and other loads require reactive power to convert the flow of electrons into useful work. When there is not enough reactive power, the voltage sags down and it is not possible to push the power demanded by loads through the lines. On 7/5/2019 4:00 PM, onielsen@... mailto:onielsen@... [EVGRAY] wrote:
Hi Mick,
I'm not sure I follow. If you mean one phased motors having a help or start winding this winding has a capacitor in series to make a phase shifted current. The big motors are three phased. For two speeds the pole pair number is changed. For reducing the start current the motor is started in star connection and switched to delta connection. I.e. the voltage is changed across the motor windings.
The inductance of the motor windings is what makes the power reactive. At high load the power becomes more active. It's like a transformer without any load. This acts like an inductor which has lagging reactive power. The current lags the voltage. When loading the transformer its secondary induces an opposite directed magnetic field which cancels the magnetic field of the primary coil. This makes the power become resistive or active or real.
Regards
Ole
---In [email protected] mailto:[email protected], <mkjekyll@...> mailto:mkjekyll@... wrote :
Ole, I was referring to the old style motors that require a certain amount of active on the grid. There are still a lot of those in factories with the tapped winding's for two speed operation like the old lathe motors. My understanding, which may be incorrect as I never worked in distribution, is that AC induction motors require some reactive power to run properly notwithstanding the lagging PF they add themselves.
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