What frequency range do the inverters operate at? I know it will vary with speed, but what would the max speed frequency be?
Anyone…anyone…
I would be very very surprised if they ever operated over 400 hz. That is to say, the alternator on the main engine. The inverters themselves are a different story. You are going from DC (rectified from the main engine alternator) back to AC, and there will be two distinct frequencies involved: one is an internal chopper, which takes the DC and converts it into pulses of power, some positive with relation to earth, and some negative. When all of these pulses are added together and smoothed out, the result is an AC current which is fed to the traction motors. The frequency of that current is basically what controls the rpm of the traction motors – and again, I would bet that that resultant current is in the 60 hz to 400 hz range; it is, at least, in variable frequency drives in many other applications. The internal chopper frequency will be considerably higher, however.
The EMD units run at roughly 100Hz at 70 mph. Are you headed toward asking about cab signal interference?
Thanks guys. No I am not headed tward signaling issues. It just dawned on me that I had no idea what the freq range was and was curious.
All you need to know to calculate is the wheel diameter, gear ratio and number of poles on the traction motor’s rotor.
Info on wheel diameter and gear ratio are available, but I have no idea how many poles there are.
Induction motors have poles?
On the rotors, that is.
Yes
Typically they behave as 2 pole motors (but 3 phase fields). Figure 3600 rpm at 60 hz. Some of them are 4 pole – figure 1800 rpm at 60 hz.