IGBT Selection Guide for Power Applications

Introduction

Insulated Gate Bipolar Transistors (IGBTs) are the workhorse of modern power electronics, combining the high-current capability of bipolar transistors with the easy drive characteristics of MOSFETs. Proper IGBT selection is critical for achieving optimal efficiency, reliability, and cost-effectiveness in power conversion applications.

This guide provides a systematic approach to IGBT selection, covering voltage rating, current capability, switching characteristics, thermal considerations, and package selection.

Step 1: Voltage Rating Selection

The collector-emitter voltage rating (Vce or Vces) is the first parameter to consider.

Voltage Classes

Voltage RatingTypical ApplicationsRecommended Margin
600VLow-voltage motor drives, 230VAC input2× operating voltage
650VGeneral purpose inverters, UPS2× operating voltage
1200V400VAC industrial motor drives, solar inverters2× operating voltage
1700VHigh-power industrial drives, wind power1.5-2× operating voltage
3300V+Traction, high-voltage industrial1.5× operating voltage

Voltage Margin Considerations

Always select IGBT voltage rating with sufficient margin:

  • DC Link Voltage: For 400VAC three-phase input, DC link voltage is approximately 540VDC
  • Voltage Spikes: Switching transients can add 20-50% to DC voltage
  • Safety Margin: Minimum 1.5×, preferably 2× maximum expected voltage
Example: For a 400VAC motor drive with DC link voltage of 540VDC and expected switching spikes of 200V, maximum voltage = 740V. Select 1200V IGBT (1.6× margin).

Step 2: Current Rating Selection

Current rating selection requires understanding both continuous and peak current requirements.

Continuous Current (Ic)

The continuous collector current rating should exceed the maximum RMS current in your application:

`` Ic(rated) ≥ 1.5 × Ic(rms, max) `

Peak Current (Icp)

IGBT modules can handle short-duration peak currents higher than the continuous rating:

  • Typical peak capability: 2× Ic for 1ms
  • Application: Motor starting, overload conditions

Current Derating

Consider current derating factors:

  • Temperature: Current rating decreases at higher junction temperatures
  • Switching Frequency: Higher frequency increases losses, requiring current derating
  • Cooling: Limited cooling capacity may require current derating
Example: For a 15kW motor drive with 400VAC input:
  • Output current = 15000W / (√3 × 400V × 0.85 efficiency × 0.85 power factor) ≈ 32A RMS
  • With 1.5× margin: 32A × 1.5 = 48A
  • Select IGBT with Ic ≥ 50A (e.g., FF75R12ME4 with 75A rating)

Step 3: Switching Characteristics

Switching performance affects efficiency and electromagnetic compatibility (EMC).

Switching Losses

Total switching loss = Eon (turn-on loss) + Eoff (turn-off loss) + Err (diode reverse recovery)

Trade-offs:

  • Fast switching: Lower losses, higher EMI
  • Slow switching: Higher losses, lower EMI

Switching Frequency

Higher switching frequency enables:

  • Smaller passive components (inductors, capacitors)
  • Better output waveform quality
  • Higher control bandwidth
But also causes:
  • Higher switching losses
  • Increased EMI concerns
Guideline:
  • Motor drives: 4-16kHz (audible noise consideration)
  • Solar inverters: 16-50kHz
  • Induction heating: 20-100kHz

Step 4: Thermal Considerations

Proper thermal design is essential for IGBT reliability.

Junction Temperature

Maximum junction temperature (Tj,max) for most IGBTs: 150°C to 175°C

Recommended operating Tj: <125°C for long-term reliability

Thermal Resistance

Total thermal resistance from junction to ambient:

` Rth(j-a) = Rth(j-c) + Rth(c-s) + Rth(s-a)

Where:

  • Rth(j-c): Junction-to-case (specified in datasheet)
  • Rth(c-s): Case-to-heatsink (thermal interface material)
  • Rth(s-a): Heatsink-to-ambient (heatsink specification)
`

Power Dissipation

Total power dissipation:

` P(total) = P(conduction) + P(switching)

P(conduction) = Vce(sat) × Ic(average) P(switching) = (Eon + Eoff + Err) × fsw ``

Example Thermal Calculation: For FF300R12ME4 at 200A, Vce(sat) = 1.75V:

  • P(conduction) = 1.75V × 200A = 350W (per IGBT)
  • P(switching) at 10kHz = 25mJ × 10000 = 250W
  • P(total) = 600W
With Rth(j-c) = 0.15°C/W and Tj,max = 150°C:
  • ΔT(j-c) = 600W × 0.15°C/W = 90°C
  • Maximum case temperature: Tc = 150°C - 90°C = 60°C
This requires substantial heatsinking and possibly forced air or liquid cooling.

Step 5: Package Selection

IGBT package affects current capability, thermal performance, and mechanical integration.

Common Package Types

PackageCurrent RangeApplications
TO-24720-100ADiscrete IGBTs, low power
EconoDUAL 350-600AIndustrial motor drives, general purpose
PrimePACK 3+450-3600AHigh-power renewable energy, traction
EasyPACK15-100AServo drives, small inverters
IHM/IHV15-75AInduction heating, welding

Package Considerations

  • Creepage/Clearance: High-voltage isolation requirements
  • Thermal Interface: Direct bond copper (DBC) substrate, baseplate options
  • Connections: Screw terminals, spring contacts, press-fit
  • Isolation Voltage: Typically 2500VAC for 1 minute

Selection Example: 50kW Motor Drive

Requirements:

  • Input: 400VAC three-phase
  • Output power: 50kW
  • Switching frequency: 8kHz
  • Ambient temperature: 40°C
Selection Process:
  • Voltage: DC link ≈ 540VDC, select 1200V IGBT
  • Current:
    • Output current = 50000 / (√3 × 400 × 0.9 × 0.85) ≈ 94A RMS
    • With margin: 94A × 1.5 = 141A
    • Select 150-200A IGBT
    3. Package: EconoDUAL 3 for industrial application
  • Specific Part: FF200R12ME4 (1200V, 200A)

    • Conclusion

    IGBT selection requires systematic evaluation of voltage, current, switching, thermal, and package requirements. By following this guide and consulting datasheets, you can select the optimal IGBT for your application.

    For personalized assistance, contact our power electronics FAE team at michael.wang@elec-distributor.com or +86 15013702378.