on my pt system i needed to be able to have a control system that allowed me to plug in the cabinet, set up the coil, and push a button to start and stop the system from a distance. many systems i've seen have four or five pieces of control cabinets, power supplies and other pieces parts all hooked together with various cables, wires, leads stretched all about. i decided to put as much as posible into the cabinet housing my pt, capacitor and spark gap.

using a fan blown static or rotary gap, it is preferable to have the fan or motor come up to speed before the main transformer power is applied, this way your airflow across the gaps is at max to allow a steady quenching.

when i push the on button it closes a 120v conection that energizes a square D "ice cube" relay that closes and puts power to my muffin fan on my static gap and also starts a timer relay set for three seconds delay on. when the fan has come up to speed for three seconds, the timer relay closes sending 120v control power to bring in the main joslyn clark contactor that sends the 80v from my twin 1.5kva step down transformers, to the 300-1 potential transformer mounted under the controls.

when the on button is pushed and the square D relay comes in, power is also passed through one of the normaly open contacts of the relay across a normally closed contact on a second "ice cube" and back to the coil of the first relay. this is called a "latching circuit", what happens is that the button on the pendent is only momentary so power passes only as long as i hold the button closed, this would get very tough on the thumb after a while. so the latching circuit in effect holds the button for me, in the pendent, the off button is wired the same as the on except that the power passes to the second, or latching relay. when i press the off button the latch relay coil is energized, closing the Normaly Open contacts, but it also opens the Normaly Closed contacts, this breaks the circuit passing power to the first relays coil and drops the power out allowing the contacts to open. opening the latch.

i really liked this setup because i allways have my thumb on the off button once started and while making adjustments. i figured that if i ever accidently took a bad strike or something, my muscles would tighten and i would inadvertantly push the off button, dropping all power to the system.

also in the circuit i have two control power fuses, home made chokes, and a siemens thermal trip 10-20 amp adjustible breaker. this breaker passes the 120v to the step down transformers and is also used as a main disconect for the pt, alowing me to do control circuit adjustments or testing, with no power available to the main contactor.

below i have a rough schematic of the control circuit drawn in windows paint, i will try to draw one in multi sim and get it on here, but i'm not to good? any further questions feel free to email me! for one good place to get relays, sockets, timers and such, i have a catalog from surplus center, but i will have to look for it and get back to you.

all contact numbers are actual numbers of the square d bases of the relay andpoter brumfield base for the timer. your numbers may be different but just use the N.O. or N.C., Normaly Open or Normaly Closed contacts of the relays you use.

if you find a pendent or use push buttons that have both normaly open and N.C. contacts, you could use the N.C. contact of the off button for the latch contact, thus eliminating the latch relay. my pendent didn't have such a luxuary so i hade to use the second unit, oh well?

one thing to think about in finding relays, is to try to get some with a couple N.O. and N.C. on each, this way you can power lights, use as interlocks, (start camera???) or whatever just by running a wire from the daisy chained control terminal strip to the contact and to the light.


	control circuit on my pt system i needed to be able to have a control system that allowed me to plug in the cabinet, set up the coil, and push a button to start and stop the system from a distance. many systems i've seen have four or five pieces of control cabinets, power supplies and other pieces parts all hooked together with various cables, wires, leads stretched all about. i decided to put as much as posible into the cabinet housing my pt, capacitor and spark gap. using a fan blown static or rotary gap, it is preferable to have the fan or motor come up to speed before the main transformer power is applied, this way your airflow across the gaps is at max to allow a steady quenching. i opted to use a 25' cord with a pendent housing two momentary push buttons, on\off. when i push the on button it closes a 120v conection that energizes a square D "ice cube" relay that closes and puts power to my muffin fan on my static gap and also starts a timer relay set for three seconds delay on. when the fan has come up to speed for three seconds, the timer relay closes sending 120v control power to bring in the main joslyn clark contactor that sends the 80v from my twin 1.5kva step down transformers, to the 300-1 potential transformer mounted under the controls. when the on button is pushed and the square D relay comes in, power is also passed through one of the normaly open contacts of the relay across a normally closed contact on a second "ice cube" and back to the coil of the first relay. this is called a "latching circuit", what happens is that the button on the pendent is only momentary so power passes only as long as i hold the button closed, this would get very tough on the thumb after a while. so the latching circuit in effect holds the button for me, in the pendent, the off button is wired the same as the on except that the power passes to the second, or latching relay. when i press the off button the latch relay coil is energized, closing the Normaly Open contacts, but it also opens the Normaly Closed contacts, this breaks the circuit passing power to the first relays coil and drops the power out allowing the contacts to open. opening the latch. i really liked this setup because i allways have my thumb on the off button once started and while making adjustments. i figured that if i ever accidently took a bad strike or something, my muscles would tighten and i would inadvertantly push the off button, dropping all power to the system. also in the circuit i have two control power fuses, home made chokes, and a siemens thermal trip 10-20 amp adjustible breaker. this breaker passes the 120v to the step down transformers and is also used as a main disconect for the pt, alowing me to do control circuit adjustments or testing, with no power available to the main contactor. below i have a rough schematic of the control circuit drawn in windows paint, i will try to draw one in multi sim and get it on here, but i'm not to good? any further questions feel free to email me! for one good place to get relays, sockets, timers and such, i have a catalog from surplus center, but i will have to look for it and get back to you. all contact numbers are actual numbers of the square d bases of the relay andpoter brumfield base for the timer. your numbers may be different but just use the N.O. or N.C., Normaly Open or Normaly Closed contacts of the relays you use. if you find a pendent or use push buttons that have both normaly open and N.C. contacts, you could use the N.C. contact of the off button for the latch contact, thus eliminating the latch relay. my pendent didn't have such a luxuary so i hade to use the second unit, oh well? one thing to think about in finding relays, is to try to get some with a couple N.O. and N.C. on each, this way you can power lights, use as interlocks, (start camera???) or whatever just by running a wire from the daisy chained control terminal strip to the contact and to the light. i hope this helps or at least gives an idea as to how one version of a "semi" remote starting control can be. marc