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#モハラジオ #TractionMotorPWMSound #NYCSubway
Car Type: New York City Subway R142, R160 (R160A, R160B)
(All files in this video are from R160A.)
Traction: Alstom ONIX 2-Level IGBT-VVVF
PWM Pattern: Asynchronous
(380 Hz → 665 Hz → 1290 Hz) → (1430 Hz ⇔ 1235 Hz)
Sound Characteristics:
At least in the speed range I recorded, asynchronous PWM is used all the time. The carrier frequency changes like 380 Hz → 665 Hz → 1290 Hz in the beginning, and after that it switches between 1430 Hz ⇔ 1235 Hz according to the train speed.
When decelerating, this pattern is turned upside down. However, since it switches to the air brake completely before stopping, the sound of 380 Hz cannot be heard so often (this case is shown in the second file in this video).
Similar Alstom IGBT traction, whose carrier frequency changes discretely during the asynchronous PWM, is used for the Washington Metro 2000/3000/6000 series and the Walsaw Metro Metropolis fleets (Walsaw cars also seem to have similar frequency values).
I wonder why this pattern is adopted, and still have no idea what happens in the higher speed range.
* 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.
I wish the day to record this crazy sound will come again.
* Sorry, I am NOT taking requests for recordings.
Posted by Ebara Express
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