By Why Module Selection Deserves Care
The power module is the most consequential component in an inverter. It sets the voltage class, the losses, the heatsink size and, in many cases, the reliability of the whole product. Choosing the wrong module late in a project costs time and money, which is why a structured selection process pays for itself. This guide walks through a repeatable method for selecting a Fuji Electric IGBT module or IPM using the X series 2-pack and 6-pack families and the X and V series IPM as the candidate set.
Step 1: Fix the Voltage Class
Start with the DC bus. A 380 to 480 V AC drive rectifies to roughly 560 to 680 V, and switching overshoot adds more, so a 1200 V device provides the necessary margin. Lower-voltage systems may use a 650 V class, while high-voltage systems move to 1700 V. Never choose the voltage class from the nominal bus alone; include the switching overshoot you expect, because the device must survive the peak, not the average.
Overshoot and Margin
The commutation loop inductance and the switching speed set the overshoot. A module shrinks the loop compared with discretes, which reduces overshoot, but the DC-link layout and capacitor placement still matter. Leave at least fifteen percent margin between the worst-case peak and the module's blocking voltage, and measure overshoot at the module terminals during validation.
Step 2: Set the Current
Continuous current plus overload current sets the current rating. A motor drive may draw 150 percent of rated current for several seconds during acceleration, and welding equipment draws large repetitive pulses. Choose a module whose rated current covers the worst case at the expected case temperature, then verify junction temperature with the thermal path. Current ratings are specified at a case temperature, so a hot environment requires derating.
Switching Frequency
Switching frequency is the next filter. Below about 15 kHz, conduction loss dominates, so a low saturation voltage device is efficient. Above 15 kHz, switching loss grows quickly, so gate drive and layout become critical. Fuji Electric's 7th-generation X series chip reduces inverter loss by around ten percent against the previous generation at the same current and frequency, which lets you raise the frequency for smaller magnetics within the same thermal budget.
Step 3: Choose the Integration Level
Fuji Electric offers three levels of integration. A 2-pack module contains two IGBT switches and their anti-parallel diodes for one half-bridge leg, giving the most circuit flexibility. A 6-pack module integrates the whole three-phase bridge in one package for a compact drive. An IPM goes further and adds the gate drive, the protection and, in some versions, a brake chopper, so a microcontroller drives it directly. The right choice depends on current level, board space, production volume and how much gate-drive work you want to own.
2-Pack, 6-Pack or IPM
Use 2-packs when you build the bridge yourself or need per-leg flexibility, 6-packs when you want the bridge integrated without the drive electronics, and IPM when you want the simplest, most compact power stage. Many designs combine a discrete IGBT module for the main drive with an IPM for an auxiliary axis.
Step 4: Confirm the Thermal Design
Thermal design decides reliability. Begin from the datasheet junction-to-case thermal resistance, add the interface and heatsink resistance, and verify junction temperature at worst-case current and ambient. The X series supports a continuous operating temperature of 175 C, but that margin only helps if the heatsink and interface are correct. Use a thin, uniform thermal interface material and mount the module flat with the specified torque.
Step 5: Validate on the Bench
Before committing to volume, build a prototype and measure gate waveforms, turn-off overshoot and case temperature under load. Compare the measured loss with the datasheet estimate and adjust the gate resistor, dead time and heatsink as needed. Measured data removes the guesswork and prevents late-stage surprises. BeiLuo's FAE team can support this validation and compare candidate modules on your operating point.
Documentation and Supply
Every Fuji Electric module BeiLuo ships is factory-traceable and includes an import declaration, a certificate of origin and a RoHS compliance file. Mainstream 1200 V modules are held in regional stock, so a validated design moves smoothly from prototype to production. Selecting the right module is the first step; keeping it supplied is the second, and BeiLuo supports both.