[Inductor-Recorded Traction Motor Sound モハラジオ録音] DART SLRV [AEG GTO-VVVF]

#モハラジオ #多変調VVVF #TractionMotorPWMSound #DART
Car Type: Dallas Area Rapid Transit SLRV
Traction: AEG 2-Level GTO-VVVF
PWM Pattern:
51P → 48P → … → 12P → Advanced PWM (Several steps. I used the word "Multi-Pulse Mode(s)" for them in this video.) → 1P
(All Synchronous)
Sound Characteristics:
This vehicle has the famous sound, which is called "multi-modulation-mode" VVVF.
In low speed range, Sinusoidal PWM is applied, and pulse modes are switched in rapid succession while reducing the magnification of carrier frequency to modulating frequency like 51, 48, ... , 12. For the first 51 pulse mode, its carrier frequency rises from 102 Hz since its modulation frequency starts from 2 Hz. On the other hand, for the subsequent pulse modes, the carrier frequency is put in the range of approximately 350 Hz to 400 Hz.
After consecutive sinusoidal PWM modes, advanced PWM modes are used (Let me omit the details because analysis of this part is very difficult). It is characteristic that the modulation rate changes discretely in this part. Also, the pattern in this part seems to change depending on the train's running condition, and the difference appears in "File 1" and "File 3" in the video.
Finally (for medium speed range and above), 1-pulse mode is used. However, it will switch to advanced PWM depending on the train operation. Moreover, I have confirmed that the sound is interrupted when the train is completely coasting.
As of October 2020, similar sounds can be heard in Los Angeles (P2000), Toronto (T1) and Lille (Breda VLC). Also it used to be heard in New York (R110A), Seattle (Breda trolleybuses), and Taipei (C301), but all of them are now retired or refurbished (including traction system replacement).
* The AC traction PWM sound shown in this video is recorded by a sensor which is placed on the floor of a train car near its traction motor. This sensor is made by myself just using a 100mH inductor.
* Due to the resolution of the spectrogram software, the frequency displayed in this video may include some error. Thank you for your understanding.
* This sound is recorded in March 2019.
* Sorry, I am NOT taking requests for recordings.
Posted by Ebara Express
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