# Jacques Schonek

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• #13013
Jacques Schonek
Participant

“First the PFCD would withdraw the power, and then store it for functional supply to the inductive motor & other loads.”
“Power Planner II employs the usage of microcontroller for increasing the power factor.”
“Electro Flow: The main competence of the system is about its design and also the usage of ladder logic response.”

These few sentences extracted from the post are just pseudo-technical assumptions, giving no information on the operation and real benefits of the devices.
This is just smokescreen used to convince non-informed public to buy inefficient black boxes supposed to save energy.

in reply to: AC Power (back to basics) #13009
Jacques Schonek
Participant

Back to the initial post on this topic, I have a few remarks:

– reactive power is a purely mathematical concept. It comes from the vector representation of voltage and current. The current component which is in phase with the voltage is the active current. The current component which is in quadrature is called “reactive” current. When multiplied by the voltage, it gives the reactive power. This is consistent with the definitions given by the International Electrotechnical Commission IEC. This is illustrated in one paper on this blog: “6/8 – Electrical equipment: improve power factor”

-reactive power does not oscillate between generator and load. In fact, when reactive power is present, the power transmitted from generator to load is positive during a part of the power line period, and negative during another part. This is illustrated in one paper on this blog: “4/8 – Electrical equipment: power harmonics, power factor”. This is why oscillation is often mentionned.

-in order to avoid confusion, let’s use the definitions used by IEC: apparent power (and not total power), active power (and not true power).

– the symbol for reactive power is “var” (with small letters). See the paper ” KVAR, kVAr or kvar? on this blog.

– transformers are rated in VA, kVA or MVA because the size of a transformer depends on the current AND voltage ratings, whatever the phase angle between voltage and current.

– motors are rated in kW because this is the mechanical power they can continuously deliver on the shaft. The number of kW of a motor is a mechanical unit, and not electrical unit. The electrical power absorbed by a motor can be calculated by taking account of efficiency.

in reply to: power factor & frequency #13212
Jacques Schonek
Participant

The Power Factor is the ratio of the active power (kW) to the apparent power (kVA). PF = kW/kVA.

The is no mention of frequency in this formula.

However, as explained by Olivier, for a given load, the power factor will vary depending on the frequency, because the impedance and the apparent power will vary.

in reply to: Harmonic Current #13211
Jacques Schonek
Participant

An harmonic current is a current which frequency is a multiple of the power system frequency. For example, a 5th order harmonic current has a frequency of 250Hz for a 50Hz system.

#12903
Jacques Schonek
Participant

Normally, an half-bridge topology is enough for both motoring and regeneration. H-bridge is necessary if you want to operate in both directions. For your application (bicycle), I guess only one direction of rotation is enough.

In order to regenerate energy, the average voltage supplied by your converter must be lower than the emf of the motor. In these conditions, the current flow will be reversed, and the motor will act as a generator.

You do not need to have a motor voltage higher than the battery voltage for regeneration. The regenerative DC to DC converter is there to supply the right voltage to the motor. If the supplied voltage is higher than the emf, you get power into the motor. If the supplied voltage is lower than the emf, you get power from the motor.

Remember that the emf is proportional to the speed. If you are running in one direction, the emf will always be positive. When the full battery voltage is applied to the motor, you are running at full speed. (Do not forget to put your helmet ;-)

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