VTTC cooling fan shuts down when coil is operating

[SalinsLV]

Hi!

I was increasing the voltage with variac and at about 160V primary (160V x 20 = 3200V secondary) the cooling fan shut down. Fan name: DELTA THA1248BE

When there are no sparks I can increase HV supply to the maximum 230V primary (230 x 20 = 4600V secondary) and the fan would still run without problems. The fan is placed below the anode of GU-5B triode. The anode doesn't touch the chassis of the fan and the wires are distant from the fan:


The arrow shows fan location:


The fan supply is a simple bridge rectifier and 2 capacitors:




I have tried shortening power supply wires and I even cut shorter PWM and RPM wires:

but that didn't help.

I suspect that the fields from the coil are what cause the fan to stop, because when there are no sparks but HV supply is on the fan runs normally. If the fields are to blame, is there a possible solution to this problem? Maybe the fan has some sort of protection that kicks in, that I'm not aware of...

[alan sailer]

There are various ferrite based toroids that can act to filter out high frequency "noise". Perhaps one of these
can be put on the fans power supply wires to absorb transients before they reach the fan motor.

A low impedance capacitor (if the fan is DC powered) hooked across the power input leads can also filter
 out noise from the tesla output.

Good luck.

Cheers.

[davekni]

I've had good luck with grounded copper foil over the motor side of the fan, over just the center motor part, with a narrow strip of foil from that center foil along the fan wire route to the edge of the fan housing.  I typically have the fan negative supply lead grounded as well.

[SalinsLV]

I've had good luck with grounded copper foil over the motor side of the fan, over just the center motor part, with a narrow strip of foil from that center foil along the fan wire route to the edge of the fan housing.  I typically have the fan negative supply lead grounded as well.

I raised the triode a few centimeters higher from the fan and covered the fan with Aluminium foil. Then connected the shield to the VTTC ground and fan negative rail.

A low impedance capacitor (if the fan is DC powered) hooked across the power input leads can also filter
 out noise from the Tesla output.

I also added capacitors. The fan still shuts down but now at a higher voltage. Previously the fan shut down at ≈160V but now it shuts down at ≈180V. I have ordered couple of zener diodes. I'll add them to the fan after i receive them.
As I have two fans in the system, the one that shuts down is 48V expensive one. The second fan is 12V and it has never shut down. Oddly the 12V fan is much closer to the coil and the 12V rail is 1,5m long.

[TMaxElectronics]

I've found that PWM controllable fans need the PWM wire forced high (or whatever level switches them on) in TCs, otherwise the fan just interprets the TCs noise as the control input. On my first SSTC I could actually control the fan speed with the interrupter duty cycle because of this You can of course also try using a non-pwm controllable fan.

[johnnyzoo]

I have seen low-voltage "brushless DC" fans slowing down or turning off due to RF field. Remember, they contain electronics, basically a mini inverter that runs the three-phase motor.

Capacitors, ferrites, chokes, foil, overvoltage clamping elements are all worth trying, and also connect the PWM signal as said above.

Some fans are less sensitive as you already found out. If all else fails, a fan with no electronics won't be affected much by the tesla coil fields.

[MRMILSTAR]

I use an old-fashioned AC muffin fan with no electronics that is about 30 years old on my 833C VTTC. The fan is located about 4 inches to the side of the tube. Its always worked perfectly.

As others have hinted, I think the solution is to use a fan with no electronics.

[TMaxElectronics]

As others have hinted, I think the solution is to use a fan with no electronics.

I agree that is probably the best solution. My 2m 20kW coil is using two old school mains powered fans too and they haven't caused any problems either. Plus those will usually be much more powerful than most fans made for PCs (just the fans draw like 250W, more than my first sstc lol).

[SalinsLV]

I've found that PWM controllable fans need the PWM wire forced high (or whatever level switches them on) in TCs, otherwise the fan just interprets the TCs noise as the control input. On my first SSTC I could actually control the fan speed with the interrupter duty cycle because of this You can of course also try using a non-pwm controllable fan.

I just tried connecting 5V to the PWM control pin and the fan still shuts down. I'll later replace the fan with AC one. Thanks for the replies!

[NerdlabsMadScience]

I'm using a similar fan on my 1kw eimac 3cx5000a7 VTTC. it's several inches away from the secondary coil and still functions fine. try cutting off the PWM signal wire so id doesn't act like an antenna.