Analysis of the Advantages and Disadvantages of SiC MOSFET and IGBT

The efficiency bottleneck of traditional welding machines

Low switching frequency limitation

Traditional IGBT welding machines are limited by a switching frequency of 20kHz or below, resulting in large transformers, high copper losses, and overall machine efficiency generally below 86% (in accordance with the GB28736-2019 secondary energy efficiency standard), which cannot meet the energy-saving requirements of modern industry.

High proportion of dynamic loss

During the hard-switching process, the IGBT generates significant trailing current and reverse recovery losses, which account for 35% – 45% of the total system losses, severely restricting the design of high power density.

Redundant Cooling System

The junction temperature of the IGBT module is usually limited to below 125°C. Therefore, a large heat sink needs to be equipped, which increases the size and cost of the equipment (the cooling system accounts for 15%-20% of the total weight of the entire device).

Challenges in High-Temperature and High-Frequency Application Scenarios

Thermal Management Challenges

Under the continuous high-current operation of the welding machine, the junction temperature of power devices often exceeds 150°C. Traditional silicon-based devices experience problems such as a decrease in carrier mobility and non-linear growth of conduction resistance.

Electromagnetic Compatibility Requirements

High-frequency switching (>500 kHz) generates severe di/d and dv/dt noise. The drive circuit design needs to be optimized to suppress ringing and voltage overshoot (the typical value should be controlled within 120% of the rated voltage).

Arc Stability Requirements

The high-frequency inverter has extremely high requirements for the response speed of the control loop. The PWM modulation delay needs to be less than 200ns to ensure the stability of the droplet transition process and prevent welding spatter.

The core characteristics of SiC MOSFET

RDS(on) optimization design

The SiCMOSFET adopts a planar gate structure, with the on-resistance as low as 8mQ (as in the XXX model), which is more than 60% lower than that of traditional IGBTs, significantly reducing on-state losses. Taking a 500A welding machine as an example, the power consumption of a single tube can be reduced by more than 15W.

Zero reverse recovery characteristic

The SiC material does not have the problem of minority carrier recombination. The switching loss is only 1/5 of that of silicon-based devices. Under a 70kHz high-frequency condition, the overall efficiency of the module is increased by 4-5 percentage points, effectively solving the thermal accumulation problem caused by the high-frequencyization of traditional welding machines.

Dynamic characteristics

By optimizing the gate drive voltage (recommended +18V/-4V), a switching speed of the order of nanoseconds can be achieved, significantly reducing the switching loss. This is particularly suitable for pulse welding scenarios.

Advantages of High-Frequency Switching Performance

Switching Frequency Breakthrough

Supports a maximum operating frequency of 200kHz (1GBT typically ≤ 20kHz), reducing the transformer volume by 60% and the overall machine weight by 30%. For example, the NBC-500SiC welding machine with a 70kHz design has an inductance requirement of only 1/4 of the traditional solution.

Harmonic Suppression Capability

High-frequency switching results in a smoother current waveform, with THD (Total Harmonic Distortion) controlled within 3% (about 8% for IGBT solutions), meeting strict EMC standards such as EN61000-3-12, and is particularly suitable for high-end models exported to the EU.

Response Speed Enhancement

The typical switching-on delay time is 25ns (compared to 35ns for similar products), combined with digital control, enables an arc response of 0.1ms level, precise control of the droplet transition process, and improvement in the control level of spatter in stainless steel welding.

Economic Analysis of SiC MOSFET

Power saving efficiency: 2.56KVA/26.13KVA, approximately 9.8%.

Assuming each day works for 8 hours and the price of each kilowatt-hour is 1 yuan. Then the daily electricity savings would be:

2.56 x 8 x 1 = 20.48 yuan.

The monthly electricity savings would be: 20.48 x 30 = 614.4 yuan.

If used normally for 110 days, the saved money would be sufficient to purchase a silicon carbide welding machine.

If compared with a third-level energy-consuming welding machine, only the electricity savings in 60 days would be enough to buy a silicon carbide welding machine.