DC motor ripple voltage..

hi folks...
im working with dc motors; this i want to clarify:
1.) in uncontrolled-rectified power supply, What is the percentage tolerance of RIPPLE VOLTAGE associated with the rectified power supply to the dc motor windings?
2.) in exceed with this tolerance, if any, does it really creates audible audio disturbance(electrical humming sound) or even unusual vibrations on the machine?
3.) If it really creates disturbance, what would it then result to?
4.) how can we reduced, if not illiminated, or protect the machine out of this phenomena? any recomendations?
5.) in exceed with this RIPPLE VOLTAGE, does the winding itself can reduce or compensate such ripples by using the winding as a filtering device to smoothen the dc supply, knowing the fact that dc windings are inductive?

ill appreciate your comments and suggestions..

thank u very much.

regards.

 

[jbartos]

Suggestions marked by ///\\fbjavier (Electrical) Oct 6, 2002
hi folks...
im working with dc motors; this i want to clarify:
1.) in uncontrolled-rectified power supply, What is the percentage tolerance of RIPPLE VOLTAGE associated with the rectified power supply to the dc motor windings?
///The percentage of ripple is dependent on the power supply number of phases, and ripple filtering.\\ 2.) in exceed with this tolerance, if any, does it really creates audible audio disturbance(electrical humming sound) or even unusual vibrations on the machine?
///Most likely, it will.\\ 3.) If it really creates disturbance, what would it then result to?
///Noise may be controlled by OSHA or equivalent agency, and vibration reduces the lifecycle of the equipment.\\\
4.) how can we reduced, if not illiminated, or protect the machine out of this phenomena? any recomendations?
///The better filtering of the ripple, increase number of phases, e.g. from one to three, from three to six, etc.\\ 5.) in exceed with this RIPPLE VOLTAGE, does the winding itself can reduce or compensate such ripples by using the winding as a filtering device to smoothen the dc supply, knowing the fact that dc windings are inductive?
///The ripple is effectively reduced by a capacitor element in the ripple filter.\\\

 

[geezer]

In a DC motor, the armature, in conjunction with the motor back-EMF, acts like an LC filter, with the motor speed proportional to the average of the rectified applied voltage. Consequently, a common means of controlling the speed of a DC motor is to replace the bridge rectifiers with SCR's, varying the phase angle of the SCR firing to control the speed of the motor. This means of control does emit an audible hum, usully swamped out by gear noise of the machinery being driven. Quiet operation requires a PWM supply operating above the audible range of about 20 KHz.

 

[geezer]

Argh! That should be "inertia", not "motor back-EMF". The armature inductance together with the armature inertia acts like an LC filter. Sorry.

 

[jbartos]

Suggestion: Visit

http://www.elevatordrives.com/elevator/resources/dsd412_app106_ripplefilter.pdf

http://www.quio.wtal.de/motorkartenleser/download/MTM-5H-0101.pdf

http://electron.toulouse.iufm.fr/iufm/Documentation/Perche/L292_b.pdf

http://www.infineon.com/cmc_upload/documents/025/392/SAE_01_MotorEMC_e.pdf

etc. for more info