USER MANUAL MOTOR DRIVES

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6. INDUCTORS

Product-Accessory Compatibility

Product

Sinus Penta

Penta Marine

Iris Blue

Solardrive Plus

Inductors

√

√

√

√

Comments

The DC inductors may be installed only on S05 2T and S12 2T/4T

AC input inductors and DC inductors

– only if a power supply source other than the PV field is envisaged

Table 7: Product – Inductors compatibility

Figure 49: Wiring diagram for optional inductors

6.1. Input Inductors

We suggest that a three-phase inductor, or a DC-BUS DC inductor, be installed on the supply line to obtain the following benefits:

- limit input current peaks on the input circuit of the inverter and value di/dt due to the input rectifier and to the capacitive load of the capacitors set;

- reducing supply harmonic current;

- increasing power factor, thus reducing line current;

- increasing the duration of line capacitors inside the inverter.

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Harmonic currents

The shapes of the different waves (current or voltage) may be expressed as the sum of the basic frequency (50 or 60Hz) and its multiples. In balanced, three-phase systems, only odd harmonic current exists, as even current is neutralized by symmetrical considerations.

Harmonic current is generated by non-linear loads absorbing nonsinusoidal current. Typical sources of this type are bridge rectifiers

(power electronics), switching power supply units and fluorescent lamps.

Three-phase rectifiers absorb line current with a harmonic content n=6K±1 with K=1,2,3,… (e.g. 5th,7th,11th,13th,17th,19th, etc.). Harmonic current amplitude decreases when frequency increases. Harmonic current carries no active power; it is additional current carried by electrical cables. Typical effects are: conductor overload, power factor decrease and measurement systems instability.

Voltage generated by current flowing in the transformer inductor may also damage other appliances or interfere with mains-synchronized switching equipment.

Solving the problem

Harmonic current amplitude decreases when frequency increases; as a result, reducing high-amplitude components determines the filtering of low-frequency components. The better way is to increase lowfrequency impedance by installing an inductor. Power drive systems with no mains-side inductor generate larger harmonic currents than power drives which do have an inductor.

The inductor may be installed both on AC-side, as a 3-phase inductor on the supply line, and on DC-side, as a single-phase inductor installed between the rectifier bridge and the capacitor bank inside the inverter. Even greater benefits are obtained if an inductor is installed both on AC-side and on DC-side.

Unlike DC inductors, AC inductors filter high-frequency components as well as low-frequency components with greater efficiency.

CAUTION

A DC inductor can be connected to inverters sizes S15, S20, S30. This must be specified when ordering the equipment (see the Power Terminals Modified for a

DC Inductor in the Installation Guide).

CAUTION No DC inductor can be installed in S05(4T) inverters.

CAUTION

When a DC inductor is used, it can happen that no braking resistor can be connected when an external braking unit is connected, and vice versa (see the

Power Terminals Modified for a DC Inductor in the Installation Guide).

Harmonic currents in the inverter power supply

The amplitude of harmonic currents and their incidence on the mains voltage is strongly affected by the features of the mains where the equipment is installed. The ratings given in this manual fit most applications.

For special requirements, please contact Ener tronica Santerno’s Customer service.

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80%

70%

60% With no inductor

With AC inductor

50% With DC inductor

40%

30%

20%

10%

5 th 7 th 11 th 13 th 17 th 19 th 23 rd 25 th

Figure 50 : Amplitude of harmonic currents (approximate values)

CAUTION

Use the input inductor under the following circumstances:

• mains instability;

• converters installed for DC motors;

• loads generating strong voltage variations at startup;

• power factor correction systems.

Use the input inductor under the following circumstances:

• when drives up to size S12 included are connected to grids with a shortcircuit power greater than 500kVA;

• with drives from size S15 to size S60P when the short-circuit power is 20 fold the inverter power;

CAUTION

• when using parallel-connected inverters;

• with Penta drives size S65 or greater, unless the inverter is powered via a dedicated transformer featuring Vdc=5% or greater;

• with modular inverters provided with multiple power supply units (sizes

S70, S75, S80 and S90).

The ratings of optional inductor recommended based on the inverter model are detailed in the section below.

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