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IGBT5-S5: F3L400R07W3S5_B59 NPC1 (I-Type), Inner and Outer Switches

IGBT5-S5: F3L400R07W3S5_B59 NPC1 (I-Type), Inner and Outer Switches

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What is NPC1 inverter? 

 

NPC1, as shown on Figure 1; is the 3-level inverter topology often referred to as “neutral point clamped Inverter”.

NPC1 inverters are used for high-voltage applications because the IGBTs are subjected to half of the DC link voltage, so the IGBTs with lower voltage ratings can be used. In an NPC1 inverter, each leg has four IGBTs with anti-paralleled diodes; each leg is completed by the addition of two clamp diodes.

Figure 1: Neutral point clamped inverter

MohammedA_41_0-1663149913566.png

 

Conduction period of outer switches vs inner switches in NPC1 leg

 

The NPC1 inverter provides three voltage levels on the output stage:

  • Positive DC bus voltage
  • Zero voltage
  • Negative DC bus negative voltage

For example, if you consider one leg operation, the positive voltage can be obtained by turning on T1 and T2, the negative voltage can be obtained by turning on T3 and T4, and the zero voltage can be obtained by turning on T2 and T3. From the operation of NPC1, it’s clear that inner switches will be conducted for a longer period compared to the outer switches and the outer switches will be switching more frequently compared to the inner switches. This means that conduction losses in inner switches are higher while switching losses are higher in outer switches. To increase the efficiency of NPC1, losses must be reduced; Infineon’s F3L400R07W3S5_B59 module helps achieve this.

F3L400R07W3S5_B59 - 650 V, 400 A 3-level IGBT module

 

Figure 2: Connection diagram of NPC1

image.png

Figure 3: Typical appearance

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F3L400R07W3S5_B59 contains one IGBT in the inner and two parallel in the outer with clamping diodes to suit the NPC1 leg. Three modules together can be used to make a 3-phase NPC1 inverter. This IGBT module comes with EasyPACK™ 3B 650 V, 400 A with TRENCHSTOP™ 5, integrated NTC, and PressFIT contact technology which suits 1000 V DC PV systems in three-level NPC1 topology for a power rating of up to 125 kVA, 400 V or 150 kVA, 480 V. The potential application of this module is solar PV inverters. This module offers electro-mechanical benefits and reduces losses.

How does F3L400R07W3S5_B59 reduce the losses?

 

This module comes with the S5 and L5 technology switches. High conduction losses in the inner switches are minimized by using L5 technology switches and high switching losses in outer switches are minimized by using S5 technology switches. Apart from this, the Al2O3 substrate is used with low thermal resistance, which helps to control the junction temperature. Refer to the F3L400R07W3S5_B59 datasheet for more details. The outer switches are used in parallel to meet the required load current and to reduce losses.

Two switches in parallel vs single switch in outer

 

The inner switches with the L5 technology have a continuous current rating of 255 A

The outer switches of S5 technology have a continuous current of 130 A. To meet the required current, two switches are connected in parallel.      

Can L5 technology switches be replaced with S5 technology switches?

 

The L5 technology switches can also be used but the overall losses will increase.  The following calculation shows how two different technology switches reduce the losses.

Switching loss = (Eon+Eoff) * Fsw

For switching frequency of 15 kHz:

Parameter

S5 technology

L5 technology

Units

Eon

1

1.06

mJ

Eoff

0.78

5.24

mJ

Switching loss

26.7

94.5

W


This calculation shows that S5 technology switches have a lower switching loss compared to the L5 technology switches. Even if you use two switches in parallel, the resultant switching loss will be lower in S5 technology and conduction loss will be lower because of current sharing. That is the reason why the outer switches are in parallel for the F3L400R07W3S5_B59 module.

This indicates that the F3L400R07W3S5_B59 module offers better performance in terms of increased efficiency by using two different technology switches.

 

Community Translation: IGBT5-S5: F3L400R07W3S5_B59 NPC1 (I-Type)の外側スイッチが並列になる理由(KBA236129)

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