Electrical Projects Television interference caused by the universal motors used in vacuum cleaners, sewing machines, and other appliances can usually be eliminated by connecting a filter between the power outlet and the power plug of the offending appliance. In the filter circuit shown LI and L2 are 8.8 uH choke coils and capacitor C is a 0.05 uF paper-dielectric type with a dc breakdown rating of 2000V. The components can be fitted in an outlet box to which a single female ac receptacle is mounted.

If the appliance proves faulty, simply solder a small disc capacitor (0.01 uF) across the ac terminals within the body of the appliance. A leaking power cable shield must be repaired at the point of leakage. Considering the reward of interference-free reception, this inexpensive, easy-to-build tester should prove a most worthwhile project.

The filter readily passes 60 Hz ac but offers resistance to the passage of the high-frequency ripple generated by the motor commutator and brushes.

Home > Electrical Projects > Tools And Components > Tvi Filter For Appliances Employing Universal Motors

Febuaury 11, 2012