PowerEsim - free on-line switch mode power supply SMPS, circuit and transformer design, calculation, simulation software. More than 100 circuits and topologies are available with real constructed transformer. It provides a virtual laboratory environment for users to wind and place every single turn of a transformer, and with the help of tens of thousands real modeled component on the market, user can simple pick and place the real component and stuff into the circuit, within a fraction of a second, our server will immediately return the result to the user. It is even faster than modifying prototype in real environment, and more than that is no worry of getting explosion of the prototype on real bench. No abstract concept or theories are needed to use this tool, as in real world, the basic thing to define a transformer is how wires in a core, not Maxwell's equations, or part No. of a MOSFET make the different, one doesn't need semiconductor physics to change a part. The most important part of a theory is the result itself. With "Result Oriented Design Approach", it can yield very high quality design in a very short time. While expertise can always use it to optimize a more efficiency solution or lower costs design with the same performance. It turns the pre-design phase from days to minutes and also a very good verification tool for the final design. In real laboratory, engineers can feel the heat, measure the stress, wind real transformer or wait and see how long the unit getting burned. With our seamless integration of different tool, e.g. thermal, MTBF, Life, DVT, Waveform, etc., user can do the same things in PowerEsim virtual environment.