I need to build an inverter to convert 24V to 115V AC, three phase. The load is a gyro, which is a motor, so I suppose its inductive. I dont know if this means it needs to be a pure sine wave output or if it makes it able to handle a square wave output or a sine wave with harmonics. Anyone know what a simple way to make one of these might be? Or an off the shelf unit?
The inverters I built to test gyros were all sinewave. I used a shift register, then low pass filters and class B audio amplifiers -- brute force lab setup, not suitable for flight or robotic apps.
You might consider the shift register and LPF's (or a uP synthesizing the three phases) followed by class D audio amps now available.
I have used a Johnson counter, a few gates, three opamps and a three phase transformer (surplus) to produce three phase 400Hz 115V AC for gyro testing. The wave form looks like: ---- -- -- ---- i.e. 0 for 1/6, + for 2/6, 0 for 1/6, - for 2/6 of the cycle. Done decently this wave form has no even harmonics and no third, nineth, ... So the lowest harmonic is the 5th and it's already getting pretty small. The transformer and gyro made no complaints.
Ted
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