Comparison test of IGBT7 and IGBT4 in servo drive

As the latest generation of Infineon’s IGBT technology platform, IGBT7 has always been a concern for engineers in terms of performance comparison with IGBT4. In this paper, through the test of FP35R12W2T4 and FP35R12W2T7 in the same platform servo drive, the junction temperature comparison of IGBT4 and IGBT7 under the same working conditions is obtained. The experimental results show that the junction temperature of IGBT7 is lower than that of IGBT4 in the comparison test between continuous high-power load conditions and inertia disk load conditions.

Comparison test of IGBT7 and IGBT4 in servo drive

As the latest generation of Infineon’s IGBT technology platform, IGBT7 has always been a concern for engineers in terms of performance comparison with IGBT4. In this paper, through the test of FP35R12W2T4 and FP35R12W2T7 in the same platform servo drive, the junction temperature comparison of IGBT4 and IGBT7 under the same working conditions is obtained. The experimental results show that the junction temperature of IGBT7 is lower than that of IGBT4 in the comparison test between continuous high-power load conditions and inertia disk load conditions.

The servo drive system has fast response speed, high overload multiples, miniaturization and high power density trends that put more stringent requirements on power devices. Infineon’s star product IGBT7, with its ultra-low conduction voltage drop, controllable dv/dt, and 175°C overload junction temperature, perfectly meets all the needs of servo drives. Infineon-Jingchuan-Maxim jointly developed a complete solution for servo drive based on IGBT7, which can significantly increase power density. The drive chip uses Infineon’s coreless transformer 1EDI20I12MH. Because of the unique capacitance structure of IGBT7, it is not easy to conduct parasitic conduction, so a single power supply design can be used, which simplifies the drive design to the greatest extent. The main control MCU adopts XMC4700/4800, and the motor position detection adopts TLE5109 to realize precise control of speed and position.

Servo drive prototype

Servo drive power board

Servo drive control board

In order to compare the performance of IGBT4 and IGBT7 in servo drives, we used two servo drives on the same platform, equipped with FP35R12W2T4 and FP35R12W2T7 with the same PIN layout, under the same dv/dt conditions (dv/dt=5600V/us) ,carry out testing.

We have designed two typical working condition comparison schemes to compare the junction temperature of IGBT4 and IGBT7 under the same working condition, which are the continuous heavy load comparison test and the inertia load comparison test. The thermocouple is embedded on the IGBT chip in the IGBT module to be tested, and the junction temperature of the IGBT chip can be directly read by connecting the thermocouple to the data acquisition instrument.

Continuous heavy load comparison test

Two motors are used for loading, the motor system under test is working in electric state, and the load motor system is working in power generation state;

The drivers based on IGBT4 and IGBT7 are used to drive the motor under test, and the switching frequency and output current/power of the two drivers are the same each time;

Use a power analyzer to test the input power and output power of the drive, and calculate the loss and efficiency of the drive.

Continuous large load comparison test platform

The figure below is the junction temperature comparison of IGBT4 and IGBT7 under continuous heavy load conditions.

It can be seen from this that the junction temperature difference between IGBT7 and IGBT4 is 17°C under the load of 8K switching frequency for 13 minutes. As the loading time increases, the junction temperature difference is still on the rise.

We also compared the temperature rise of IGBT7 and IGBT4 under different switching frequencies and the same output power (5.8KVA), as recorded in the following figure. The horizontal axis is the switching frequency of the IGBT; the vertical axis on the left is the temperature rise of the NTC temperature compared to the initial temperature. The vertical axis on the right is the temperature rise difference between IGBT4 and IGBT7. As the switching frequency increases, the NTC temperature rise of IGBT7 and IGBT4 becomes larger; at 10K switching frequency, the NTC temperature rise of IGBT7 is 19°C lower than that of IGBT4. can be seen. Because IGBT7 can work at a higher junction temperature, it can achieve greater output power and achieve power shifting.

Inertia load comparison test

The two motors are loaded with IGBT4 and IGBT7 respectively, the motors have the same inertia disk load, the speed from 1500 rpm to -1500 rpm is 250 milliseconds, and the steady-speed running time is 1.2s. Under steady-speed operating conditions, the phase output current is less than 0.5A; therefore, the average power in this test condition is relatively small.

The heat dissipation conditions of the motor are the same, and the switching frequency is 8kHz.

Inertia load test platform

Inertia plate load test conditions

The measured junction temperature curve is as follows:

It can be seen that the junction temperature of IGBT7 is lower than that of IGBT4 under the acceleration and deceleration operating conditions with the inertia disk. After 13 minutes of operation, the temperature rise of the driver has not yet reached the equilibrium state, and the junction temperature difference is about 7°C at this time.

Finally, we make a summary of this part of the test:

With the same output power, the junction temperature of the driver using IGBT7 is significantly reduced, allowing the size of the heat sink to be reduced, so that the size of the driver can be reduced;
If the same heat dissipation conditions are used, IGBT7 can output more power and realize power shift;
In addition, IGBT7 can work at a higher junction temperature, so it can output more power.

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