High pitch sound when accelerating/braking in EV mode

[mczajka]

I'm getting a sound like brake squeaking, except it's not as loud, and it only happens when I'm braking or accelerating in the 30-40 mph range. It's consistent when accelerating in EV mode, and when braking at speed. I'm not getting it at slower speeds or when braking hard at a stop. Doesn't happen when coasting. At higher speeds, I think because of other noises, I can't hear it as much. You can hear it with the windows open, but when the windows are closed, it's less pronounced, although when you are familiar with the sound, you can still hear it. Of course I took the car in for an oil change, wheel balance, brake check, and they didn't find anything. I may have to have them drive with me so I can point it out.

 

Any ideas or any other similar experiences? Something regen related? Something misaligned?

Edited July 25, 2014 at 04:37 PM by mczajka

[GregKet1]

It is definitely something to do with the electric motors/regen system.  My friend's dog knows when I'm coming over when I'm still a block away.  In a tunnel I can hear a whine while accelerating and when in regen-braking.

[mczajka]

That's interesting. I haven't been able to find anything about it related to our model, but I would definitely hear it in a tunnel.

 

I did find some similar things on the Prius forums. I think it was so bad on one car that they replaced the inverter.

 

I wish I could record it, but I don't think it's loud enough. Mine sounds more like a high pitch brake squeak, but it doesn't happen at slower speeds (5-15 mph).

[jeff_h]

I wish I could record it, but I don't think it's loud enough. Mine sounds more like a high pitch brake squeak, but it doesn't happen at slower speeds (5-15 mph).

 

Mine tends to make a faint high-pitched tweety bird sound around that speed that is mostly evident when in a tunnel or when the sound bounces off of a jersey wall, etc.  I don't know if it's the same sound that Mark is hearing.

 

But my wife's car does the exact same thing so I figured it was normal -- when I got my Prius back in 2005 I got the intro to strange buzzing/clicking/whirring/etc so unless a warning light appears or it sounds really loud and obnoxious, I just chalk it up to the sounds of the technology.

[FordService]

... I may have to have them drive with me so I can point it out...

 

This is a great next step, mczajka. How many miles do you have on your Fusion? Let us know how things progress; I'll be here if you need my help.

 

Crystal

[BadRock]

This is the result of the DC/AC conversion that takes place in the inverter. Depending on the switching frequency of the inverter you may experience audible noise. This is normal, they can increase the switching frequency but you overdrive the inverter and produce more heat which leads to premature component failure (IGBT) or you can decrease the switching frequency and end up with more audible noise. This is always a balancing act when tuning a drive unit. Ultimately the actual noise is the result of an AC motor operating with a no sinusoidal wave.
 

"When a motor is powered from an adjustable frequency drive using a PWM 

(Pulse Width Modulated) output waveform, the audible noise produced by the 

stator laminations has a different sound quality than with sine wave power.

The adjustable frequency drive produces an output voltage waveform made 

of high frequency pulses. The frequency of pulses is determined by the 

carrier frequency of the selected adjustable frequency drive.The motor stator 

core laminations vibrate at the carrier frequency changing the pitch of the 

audible noise. Whether the actual power level of the noise is increased due 

to a PWM waveform will depend upon the level of the applied excitation 

voltage."