Fuses and Protection for the Piano
By Spencer Chase
I have been connected to the electric grid for only about five years. Before that my electric power came from photo-voltaic panels and a back-up generator. I could play my Duo-Art anytime with no risk of surges or blackouts.
Since being connected I have had two major surge incidents when my 6,000 volt feeder line contacted a 60,000 volt transmission line due to "snow unloading". (This is how the local utility turns bad engineering into an "Act of God.") This ten-times over-voltage was enough to melt receptacle contacts and just about anything that was plugged in at the time. The utility did pay for damages and corrected the power pole problem (but when they changed poles a year later they put it back to the way it was).
My policy now is to unplug anything that is not in use whenever I leave the house. I have also installed a whole-house surge protector, for whatever that is worth. For the Duo-Art I have done the following in hopes of protecting it during a surge: I measured the current draw of the motor and installed a medium-fast-acting fuse which handles just a trifle more current. This may involve some experimenting. I then connected a bunch of MOVs across the line after the fuse and before the piano. The hope is that the voltage-clamping action of the MOVs will blow the fuse before anything happens. What do the engineers of the group think about this wishful thinking?
[ That's exactly the right way to get the best protection with varistors:
[ precede them with a carefully-sized fuse. -- Robbie
I must say, however, that the safest route is to stay off the grid alto- gether. None of my solar-powered neighbors has had power-line related problems. For a solar installation, don't forget to ground the panel mount and negative lead as protection against lightening. "Home Power" magazine can give much helpful information regarding this and other solar power topics. They have a web page (probably homepower.com).
There are some electronics that do not run well from certain inverters, but the new "pure sine wave" high efficiency inverters will power just about anything. With the older "modified sine wave" (read "modified square wave") inverters, induction motors can run a little warmer and it is a good idea to clean, lubricate and check the insulation an your 1920 motor before running it for an extended period. I would even add a thermal protector if this is a permanent installation.
Spencer Chase
[ Editors comment:
[
[ My employer shipped a big computer, with engineer, to a trade show
[ in Paris. The engineer was quite fatigued after the long flight
[ from California, and he forgot to change the computer power wiring
[ from 120-volts to 220-volts. When he flipped on the main circuit-
[ breaker something exploded within the computer console, and all the
[ power on the floor at the convention center went off!
[
[ I quickly received a panic call from France: the hard-epoxy case
[ of the varistor "surge protecter" blew apart, denting the console.
[ (The MOV was almost as big as your fist!) I advised the engineer to
[ disconnect the MOV and try again, after he corrected the voltage-
[ connection error. ... The computer was okay!!
[
[ The trade show electricians reported that the 100-ampere mains fuse
[ blew out, but the MOV did it's job: it prevented the over-voltage
[ from reaching the computer while the fuse was still conducting the
[ current.
[
[ Robbie Rhodes
|
(Message sent Fri 10 Jan 1997, 21:03:08 GMT, from time zone GMT-0800.) |
|
|
Mechanical
Music Digest™ Archives
