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240V vs 480V noise reduction? | 16 Oct 2014 | |

240V vs 480V noise reduction?

I am using the AKD series with 480V input and having some PWM noise in the system. My question is if I happen to lower the input voltage to 240V, would that reduce the noise in the system or it would stay the same?

Comments & Answers

Dan.Wolke@Koll… | Thu, 10/16/2014 - 18:03

Ryan:

When you say, "NOISE", I think your referring to acoustic noise?  Audible noise is dependent on the mechanical resonance and PWM frequency.  Dropping the bus voltage will help lessen the rise time of the PWM pulse so it will have an effect on the noise but it will also cut your max speed in half.  Here are some ideas you can try:

1.  Shift the resonant frequency of what the motor is attached to.  Some simple stiffening of the frame so it will not "sing" along with the motor.

2.  Try a line choke in series with the motor's three phases.  Ferrite donut setup in a common mode filter could be enough.

3.  Lower the current loop gain, IL.KP.

4.  If the motor makes noise in velocity or position mode but not in torque mode, you could be hearing something other than PWM.  Quantization feedback noise or tuning.  In this case, try setting a low pass filter in the feedback path under 1200Hz.  You may have to lower the gains because of the lag a low pass filter will add to the system.

5.  EMI issues in the feedback cable.  Incorrectly shielded feedback cable will introduce PWM noise into the system. 

Dan Wolke

Mike_Kilroy | Tue, 08/25/2015 - 19:13
If on the other hand the OP meant electrical noise, then, YES, reducing the supply voltage from 460 to 230v will indeed reduce the noise - significantly!

I look at it this way:  P=V^2/Z  so if you cut the V in 1/2, the Power in the noise pulses into the same Z impedance will reduce by a factor of FOUR TIMES.
 
Of course identifying the SOURCE of the electrical noise and then addressing it with the many known noise reduction schemes available will also reduce the noise.

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Ryan Herman
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