230V to 110V for Synchronous Motor

Did a little more wiring today. It consisted of connecting one of the female IEC socket in the front panel to the step down transformer on the second level of the tesla coil. I used a length of standard 3A 2 core round black flex. The synchronous motor is rated at 7.5W at 110V so by the equation

                  Power (Watts) = Current (Amps) X Voltage (Volts)

            so   Current (Amps) = Power (Watts)
                                                ------------------
                                                Voltage (Volts)

                                             = 7.5
                                                ----
                                                110

                                             = 0.068 Amps

So, as you can see it draws very little current and even the lightweight 3A cable is a bit of an overkill.

The top IEC socket will supply 240V to the step down transformer which in turn will supply 110V to the synchronous motor. The transformer was sourced from Newlec and came in panel form (uncased) but mounted on a pressed steel bracket. I removed the bracket so I could mount the transformer on a perspex base. This meant that I had to remove the connection strip. This task was undertaken several months back and I thought it would be wise to check that the connections were correct and the transformer is doing what's expected, also a good reason to play with my Xmas present.

The transformer has inputs for 230V and 240V with an output of 110V. I decided to supply a 50Hz AC voltage across the 230V inputs and measure the output of the terminals marked as 110V. I used the function generator built into my oscilloscope to supply this signal to the transformer at a very safe amplitude of about 3 volts. The same signal was feed into channel 2 on the oscilloscope.

The oscilloscope probe was plugged into channel 1 and then connected across the 110V output terminals. With the same volts per division set on both channels and the scope set to dual I could view the input and output waves at the same time. I did take a pic to show you the result but my camera only got an image of a few dots on the oscilloscope screen due to the high speed of the trace. So I took a quick video with my Sony Bloggie.

As you can see, the terminal connection are correct and the transformer is stepping down the voltage by  a factor of about 2 so 230V would be output at about 110V.

I can now finish the wiring to the transformer with confidence. Very pleasing to see actual inputs and outputs on the oscilloscope screen also interesting to see how the 2 signals stay in phase.

Terry Filter finished

More brass bolts arrived today plus another parcel from Teslastuff.com






I had been looking for some copper or brass electrical lugs for ages. I wanted some that looked a little vintage, similar to the ones used by Alan at Teslastuff in his Tesla coil plans. I didn't have any success and they weren't for sale on Teslastuff.com so I emailed Alan who replied "How many you want?" I ordered plenty as I'm sure I will use more throughout the rest of the build and the price from Alan was very reasonable.






I used five of the lugs and replaced the 2 nylon bolts through the outside safety gap insulators with brass bolts. Also completed the wiring, think you will agree, the finished filter looks amazing.

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Terry Filter comes together

Covered the 200mm x 320mm x 5mm black acrylic Terry Filter base with a coating of masking tape which will protect against scratching while drilling and allows me to mark up all the holes. After a trial placing of all the Terry Filter components the board was marked for drilling.



The main pcb and the 2 long resistors will be mounted on 1" high ceramic stand offs which require 4mm holes. The completed Terry Filter module will also be mounted on 1" stand offs, 6 in total. With the board marked up I watched the pretty uneventful start of the British grandprix then made my way out to the garage to drill out the holes.



The board was placed on a flat piece of ply offcut for drilling which prevents the drill bit from damaging the back of the acrylic as it emerges.



When drilling lots of varying size holes I find it useful to mark hole diameters on the work. After drilling the masking tape was removed to reveal a pristine piece of black acrylic with clean tidy mounting holes hopefully in the right places.



First trial fit of the components goes well, all holes line up nicely.



Still waiting for some brass bolts and copper lugs to enable the final assembly.



The safety gap ceramic posts are held in place by 65mm nylon bolts that screw through the base and up into threads in the brass balls. I may change to using metal bolts as the nylon bolts flex and do not hold the safety gap assembly as firm as I would like.



Next job is to make the electrical connectors between the pcb, resistors and terminal posts.



Think it turned out pretty good.

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Terry Filter Safety Gap

Today I picked up a parcel from the local Royal Mail depot. Inside was four long awaited 60mm bolts (should have been 8), least I can make a start on the safety gap. First I need to tap 2 holes through the 2 1" brass balls obtained from Teslastuff.com. The holes need to be 5mm which is the size required if tapping out to M6 with 1.0mm threads. The pic below shows how I mounted them for drilling.









I screwed in the bolt to the existing tapped hole to help me drill at 90 degrees to the existing hole. The bolt also prevented the brass ball spinning in the chuck jaws during drilling. It was easy to find the centre point for drilling as I could spin the work in the chuck to show any mis-alignment. After drilling with the centre drill I drilled a 5mm hole completely through each ball.









Next I tapped the holes out to M6 1.0mm threads. Note the plastic jaw covers on the vice to prevent marking my balls!!!









I then polished my balls by mounting them onto a threaded stud held in the chuck and spinning them up against various grades of emery cloth.









The finished articles almost ready to mount on ceramic insulators on the Terry Filter.









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