Hey guys n girls, Does anybody know why the class 700 has this beep beep as it drives and brakes under 30mph? Thanks
I would hazard a guess and say some sort of “chopper” control system to regulate the electrical side of things?
So the noise is related to the VVVF drive (Variable Voltage Variable Frequency). Not sure why the exact noise but it comes from the Inverters that are taking the DC from the Traction bus and converting it to AC at varying frequencies and voltages (hence VVVF) to drive the motors at the correct speed and torque. Older 350/360/380 series do it on AC, 700s seem to run a different inverter profile on AC, presumably as more power is available. (AC units will take power from the overhead wire and reduce it to around 1500V DC for the traction bus before it gets fed into the inverters. VVVF is a rabbit hole and TBH I don't understand most of it, but basically DC goes in, AC comes out
