5- Power Electronics - Dual Converters

Power Electronics – Dual Converters

Twin converters are primarily present in variable pace drives $V F D s$ . In a twin converter, two converters are linked collectively again to again. The operation of a twin converter is defined utilizing the diagram beneath. It’s assumed that −

A twin converter is a perfect one $g i v e s p u r e D C o u t p u t$ at its terminals.
Every two-quadrant converter is a managed DC supply in sequence with a diode.
Diodes D1 and D2 present the unidirectional movement of present.

Contemplating a twin converter working with out circulating present, the AC present is barred from flowing by managed firing pulses. This ensures that the converter carrying the load present conducts whereas the opposite converter is blocked. Because of this a reactor between the converters isn’t wanted.

Power Electronics - Dual Converters

Battery Charger

A battery charger also called a recharger makes use of electrical present to retailer vitality in a secondary cell. The charging course of is set by the kind and measurement of the battery. Several types of batteries have completely different tolerance ranges to overcharging. The recharging course of could also be achieved by connecting it to a relentless voltage or fixed present supply.

Charging Price $C$

The charging charge is outlined as the speed of charging or discharging a battery and is the same as the battery capability in a single hour.

A battery charger is specified by way of its charging charge C. For instance, a battery charger with a ranking of C/10 would give a charging capability in 10 hours whereas one rated 3C would cost a battery in 20 minutes.

Kinds of Battery Chargers

There are numerous sorts of battery chargers. On this tutorial, we’ll take into account the 5 essential sorts.

Easy chargers − Operates by supplying a relentless DC energy supply into the battery being charged.
Quick chargers − Makes use of management circuitry to charger the battery quickly and within the course of forestall the battery cells from harm.
Inductive chargers − Makes use of electromagnetic induction to cost the battery.
Clever chargers − Used to cost a battery that accommodates a chip that communicates with the good charger.
Movement powered charger − Makes use of human movement to cost a battery. A magnet positioned between two springs is moved up and down by human movement thus charging the battery.

A separately excited DC motor has the following parameters: 220V, 100A and 1450 rpm. Its armature has a resistance of 0.1 Ω. In addition, it is supplied from a 3 phase fullycontrolled converter connected to a 3-phase AC source with a frequency of 50 Hz and inductive reactance of 0.5 Ω and 50Hz. At α = 0, the motor operation is at rated torque and speed. Assume the motor brakes re-generatively using the reverse direction at its rated speed. Calculate the maximum current under which commutation is not affected.

Solution −

We know that,

V d b = 3 2 π --\sqrt \times V L - 3 π \times R b \times I d b

Substituting the values, we get,

$220 = 3 \sqrt{\frac{2}{π}} \times V_{L} - \frac{3}{π} \times 0.5 \times 100$

Therefore,

$V_{L} = 198 V$

Voltage at rated speed = $220 - (100 \times 0.1) = 210 V$

At the rated speed, the regenerative braking in the reverse direction,

$= 3 \sqrt{\frac{2}{π}} \times 198 \cos α - (\frac{3}{π} \times 0.5 + 0.1) \times I_{d b} = - 210 V$

But $\cos α - \cos (μ + α) = \frac{\sqrt{2}}{198} \times 0.5 I_{d b}$

For commutation to fail, the following limiting condition should be satisfied.

$μ + α \approx 180^{\circ}$

Therefore, $\cos α = \frac{I_{d b}}{198 \sqrt{2}} - 1$

Also,

$\frac{3}{π} I_{d b} - \frac{3 \sqrt{2}}{π} \times 198 - (\frac{3}{π} \times 0.5 + 0.1) I_{d b} = - 210$

This gives, $0.3771 I_{d b} = 57.4$

Therefore, $I_{d b} = 152.2 A$

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Power Electronics – Dual Converters

Battery Charger

Charging Price CC

Kinds of Battery Chargers

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Charging Price $C$