IGBTs (Insulated Gate Bipolar Transistors) are the core components of power electronic systems such as motor drives, inverters, and UPS units. Their correct selection directly affects the performance, efficiency, cost, and reliability of the entire system. This article provides a systematic overview of the key considerations in IGBT selection and discusses how to choose a high-quality supplier like SHYSEMI for high-performance IGBTs.
1.Understanding the IGBT’s Application Scenario: Core Requirements of Different Systems
The first step in selecting an IGBT is to clarify the application scenario, as different systems impose different requirements on IGBTs.
- Motor Drives: Focus on overload capacity, short-circuit withstand capability, and switching frequency. The high current during motor startup demands that the IGBT withstand high current stress. Additionally, a higher switching frequency helps reduce motor noise and vibration.
- Inverters (PV/Energy Storage): Prioritize conversion efficiency and reliability. High efficiency means lower conduction and switching losses, directly increasing system power generation. High reliability ensures long-term stable operation in harsh outdoor environments.
- UPS (Uninterruptible Power Supply): Emphasize high switching speed, low on-state voltage drop, and robustness. Online UPS systems require IGBTs to operate at high frequencies to achieve fast switching and clean sinusoidal output. They must also ensure absolute reliability during transitions between mains and battery power.
2. Core Selection Steps: Five Key Dimensions
Step 1: Determine the Voltage Level – Ensure Absolute Safety
*This is the top priority in selection; an incorrect voltage rating can lead to immediate failure.
- Key Parameter: Maximum Collector-Emitter Voltage (Vces)
- Selection Formula: Vces > DC Bus Voltage × Safety Factor (K)
- Factor Selection (K): Typically 1.2 to 1.5. This accounts for abnormal conditions such as voltage spikes and surges during switching.
Practical Applications:
- 220VAC System: Bus voltage ≈ 311VDC; select Vces ≥ 600V (311V × 1.5 ≈ 466V; the nearest standard rating is 600V).
- 380VAC System: Bus voltage ≈ 540VDC; select Vces ≥ 1200V (540V × 1.5 = 810V; the nearest standard rating is 1200V).
- 48V Battery System (UPS): Bus voltage ≈ 48V–60V; select Vces ≥ 100V or 150V.
Step 2: Determine Current Capacity – Ensure Continuous Operation
*Current capacity determines the system’s output power and temperature rise.
- Key Parameter: Collector Current Ic (always refer to the value at Tc = 100°C, not the ideal 25°C value).
- Selection Formula: Ic_selected > Irms × Overcurrent Factor × Design Margin
- Factor Selection:
Overcurrent Factor: Typically 1.5–2 times (to account for transient overcurrents such as motor starting and sudden load changes).
Design Margin: Typically 1.2–1.5 times (to ensure long-term reliability).
Calculation Method:
- Calculate the maximum output current: Irms = P_out / (√3 × V_out × Efficiency × Power Factor)
- Or calculate the DC input current: I_dc = P_in / V_dc
- Depending on the topology (e.g., three-phase full-bridge), the IGBT’s RMS current is approximately 0.577 times I_dc.
Professional Advice: The most reliable method is to refer to the output characteristic curve (Vce(sat) vs. Ic) in the datasheet and determine the actual current capability based on your operating junction temperature and saturation voltage drop requirements.
Step 3: Evaluate Switching Performance – Balancing Efficiency and Losses
*Switching characteristics directly affect system switching losses and EMI (electromagnetic interference).
- Key Parameters: Switching speed (turn-on time ton, turn-off time toff), switching losses (Eon, Eoff), saturation voltage drop Vce(sat).
- Technology Selection:
- Low-frequency applications (<10 kHz): e.g., high-power motor soft starters and industrial UPS. If conduction loss is the main concern, choose NPT/PT technology IGBTs, which offer lower Vce(sat).
- Medium- to high-frequency applications (>15 kHz): e.g., variable-frequency drives, photovoltaic inverters, and high-frequency UPS. Switching loss is the primary concern. Field-stop (FS) or trench field-stop (TFS) IGBTs are essential, offering fast switching speeds and low switching losses. They are the current mainstream choice.
- Trade-offs: IGBTs with low Vce(sat) have lower conduction losses but typically slower switching speeds and higher switching losses, and vice versa. Find the optimal balance based on your switching frequency.
Step 4: Thermal Management – The Key to Reliability
*All losses are converted into heat, making thermal design critical for longevity.
- Key Parameters: Maximum junction temperature Tjmax (typically 150°C or 175°C), thermal resistance Rth(j-c) (junction-to-case), and Rth(j-a) (junction-to-ambient).
- Thermal Design Formula:
- Tj = Tc + Ploss × Rth(j-c)
- Tj: Junction temperature (must be < 150°C)
- Tc: Case temperature (heat sink temperature)
- Ploss: Total losses = conduction losses + switching losses
- Selection Impact: If heat dissipation is limited (e.g., natural convection or small heat sinks), choose an IGBT with a higher current rating and lower thermal resistance, or prioritize models with lower switching losses to reduce heat generation.
Step 5: Select a Package – Matching Mechanical and Thermal Design
-TO-247: The most common high-power package, offering strong heat dissipation and easy installation. Suitable for most medium- to high-power applications.
- TO-3P: A classic power package, similar to TO-247.
- TO-220: Suitable for low- to medium-power, cost-sensitive applications.
Conclusion
Selecting an IGBT is a systematic process that requires comprehensive consideration of voltage, current, losses, thermal management, and application scenario. It is essential to start with key parameters and develop a deep understanding of system requirements.
As a company with independent IGBT chip design and development capabilities, SHYSEMI's products are already at the industry forefront, with its 1700V series leading the domestic market. By choosing a partner with both technical expertise and product advantages, you can select the most suitable IGBT for your motor drive, inverter, or UPS project, enabling the development of efficient, stable, and highly competitive products.