Quote:
Originally Posted by dieseljeep
You have to wonder what the waveforms look like using invertors to convert HV DC to 3 phase AC, such is in use today. 
Three phase AC Motors have to be a special design to be invertor duty! |
Has to do with the way the inverter creates the sinewave, its basically a high frequency duty cycle where the "full duty" is the crest of the sinewave and the motors have to be insulated to withstand the sharp spikes. I work at a plastics injection molding plant and run a 1500-ton horizontal press that uses two 500hp inverter driven motors to drive the melt extruder screws, According to the system monitor they take an average of 650 amps at 480V when melting glass infused nylon. Overall the press (Cincinnati-Milacron) takes 2.25 megawatt to run everything... this plant has 39 presses in total the largest being 3300 tons and the smallest takes 72KW. There are a number of reactors in the incoming substation just to smooth the power so it doesn't superimpose the noise on the town feeders.
Some of the presses use a triac based PWM heat control, I've never measured or looked at the plant power but when you duty cycle a 50KW set of heaters it's going to make some noise. The electric bill is $100k/week.