Real World Application of Filtering

Transcription

1 Real World Application of Filtering COPYRIGHT NOTICE: JASTECH EMC CONSULTING, LLC 2001 reproduction or translation in any form of any part of this work is prohibited unless written permission is obtained

2 WASHER PUMP DC MOTOR ASSEMBLY

3 KUTEM OMNI-CELL WITH SPECTRUM ANALYZER

4 WOODEN TEST FIXTURE

5 TEST FIXTURE INSIDE KUTEM OMNI-CELL

6 SEVEN COMPONENT MOTOR FILTER (2) Caps + (2) Inductors + (2) Beads + (1) Hi-Cap Varistor The seven component filter design includes (2) 7.5 uh inductors to limit the amount of noise that passes through and then uses (2) x-capacitors, 0.47 uf and 1000 pf, to bypass the noise to ground and to the motor case. The filter network also uses (2) ferrite beads that provide high impedance at the frequencies of the unwanted noise. The beads ferromagnetic material used in the circuit absorbs the noise and dissipates it as heat, due to A time varying magnetic field. The last component in the network is A 0.47 uf cap-varistor placed across the power leads to clamp the noise to 14 volts and bypass any remaining noise to ground.

7 DC Motor Filter Performance Comparisons dbuv Freq MHz No Filter on Motor Seven Component Filter KuTEM-Cell Ambient

8 FIVE COMPONENT MOTOR FILTER (2) Caps + (2) Ferr. Beads + (1) 0.47 Hi-Cap Varistor The five component network that starts with (2) ferrite beads that provide high impedance at the frequencies of the unwanted noise and uses A 0.47 uf cap-varistor to clamp the noise to 14 volts. (2) 0.47 uf y-capacitors y are also connected from the power leads to motor case ground to bypass the remaining noise to ground.

9 DC Motor Filter Performance Comparisons dbuv Freq MHz No Filter on Motor Five Component Filter KuTEM-Cell Ambient

10 FOUR COMPONENT MOTOR FILTER The four component filter, uses (1) 1000 pf x-capacitor x to bypass the noise to ground and the motor case. Then (2) 7.5 uh inductors limit the noise and a A second x-capacitor x at 0.47 uf bypasses the remaining noise to ground and the motor case.

11 DC Motor Filter Performance Comparisons dbuv Freq MHz No Filter on Motor Four Component Filter KuTEM-Cell Ambient

12 ONE COMPONENT MOTOR FILTER (2) 0.22 uf, L-L (1) 0.47 uf, L-G Motor X2Y 12 V The one component filter is A 1410 sized package chip. This chip is configured in what is called an X2Y layered architecture that combines an unique electrode layering method and uses an internal image plane between capacitor plates to minimize internal inductance and resistance. Alternating electrode layering allows opposing internal skin currents that are essentially 180 degrees out of phase to cancel out. This device was also designed to have its internal mutual inductance fields cancel.

13 DC Motor Filter Performance Comparisons dbuv Freq MHz No Filter on Motor KuTEM-Cell Ambient One Component Filter

14 DC Motor Filter Performance Comparisons dbuv Freq MHz No Filter on Motor Four Component Filter Seven Component Filter Five Component Filter KuTEM-Cell Ambient One Component Filter

15 Windshield Washer Pump DC Motor with X2Y Filter

16

17 Windshield Washer Pump Motor Improved Performance with X2Y & Enhanced Shielding

18 dbuv Freq MHz NO Tape NO Filter Motor W/ Conductive Tape - No Filter Motor W/ Conductive Tape & 0.44 uf X2Y

19 Here is the single point ground G1 and G2 of X2Y goes here

20 Two grounds used. Solder has been added to improve grounding when screws are tightened. Continuous trace placed under G1 and G2 of X2Y

21 EMCFEST uf X2Y dbuv Frequency MHz Ambient No filter 00008D25-1P - Motor #2 Single point ground Motor #2 Modify with X2Y Mounted on bottom Multiple ground

22 Engine Cooling Fan Motor X2Y (2) Wire Grommet in a DC Motor X2Y (2) Wire Grommet in a DC Motor A grommet or a connector is a great place to put X2Y. X2Y is shown (not) soldered between A & B with G1& G2 connected to conductive screen or lining placed in grommet. X2Y (2) Wire Grommet in a DC Motor

23 EMCFEST 2001 Engine Cooling Fan Motor X2Y

24 Engine Cooling Fan Comparison One Line Conducted Tests Current Filters vs X2Y

25 REVIEW KEY POINTS Provide a metal or metalized motor housing. This is necessary because b when filter is attached properly to the motor housing, the housing itself is used in combination with the component as a reference to cancel the noise (antenna theory). t Plastic motor housing Metalized motor housing with plastic end cap Plastic end cap Plastic end cap Improved

26 REVIEW KEY POINTS If possible, provide a metal or metalized end cap. This will help with containment of fields that can radiate around the plastic end cap and couple back onto the leads. Noise can couple outside the motor case when using a plastic end cap. A metal end cap works as a shield to contain the noise within the motor case. Improved

27 REVIEW KEY POINTS Be aware that any crimping tabs that bring the inside surface of the motor housing in contact with the outer surface of the metal end cap can couple interior case noise to the cap and degrade filtering. ing. Crimping tabs

28 REVIEW KEY POINTS Holes or slots in the motor case can radiate energy leading to component ineffectiveness. Keep the vent holes away from the brushes (noise source).

29 REVIEW KEY POINTS Here is the motor before application of small PCB. Note in this picture the leads are 180 apart Clean motor surface of any oil/etc. that would prevent a good ground

30 REVIEW KEY POINTS Small PCB is now applied and the motor leads are brought together underneath the PCB and are then brought through close together so s that the X2Y component can be soldered between leads.

31 REVIEW KEY POINTS Conductive tape has now been wrapped around motor housing and over the edge and onto the top ground area of the small pcb. This works to contain radiated noise and will focus the noise to the exit leads s and X2Y. X2Y

32 REVIEW KEY POINTS For prototyping, tape is soldered Soldering the tape in multiple areas to motor housing for lowest will improve the ground impedance. impedance ground connection. Clean motor surface of any oil/etc. that would prevent a good ground

33 MOTOR DEMO For more papers written by James P. Muccioli go to emc.com

34 LOW COST SHIELDED TEST BOX