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  • Hey all, just changed over the backend after 15 years I figured time to give it a bit of an update, its probably gonna be a bit weird for most of you and i am sure there is a few bugs to work out but it should kinda work the same as before... hopefully :)

Head Electric question

Jon Carr

Jon Carr

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Was gaffing a feature on MX, and ran into a problem with our small HMI's on the last 2 days of shooting. 3 phase 300 amp genny with a 6k 240v on 2 phases, 4k 120v on the other phase. Working great, no flickering sparked right up. Then we tapped 1.2k into one of the 6k's phases, sparked right up then turn off and on. Tapped it into the 4k's phase and wouldn't even turn on. Checked it with a tungsten light of the same amps and worked fine. But would not strike with a 1.2 or 575. Frequency was at 60, and with well over 800 ft of distro it was drawing 120v at the lunch boxes. All small HMI's were working fine on house power.

My question is what was going on where only the small HMI's would not stay on?
 
Anyone? Someone else on this site has to do electric besides just cinematography.
 
First of all, with three phase power you need to balance the loads as evenly as possible across all three legs. So you should have been trying the 1200 on the 4k leg initially regardless, not one of the 6k legs.

Second of all, it sounds like a voltage drop issue. Did you meter the end voltage at the end of that that 800ft run? HMI's especially can be picky about this.
 
Andy Jarosz said:
First of all, with three phase power you need to balance the loads as evenly as possible across all three legs. So you should have been trying the 1200 on the 4k leg initially regardless, not one of the 6k legs.

Second of all, it sounds like a voltage drop issue. Did you meter the end voltage at the end of that that 800ft run? HMI's especially can be picky about this.
Click to expand...

Wouldn't the 6k be splitting it's 45amps on both legs since it's drawing 240v? Checked the voltage at the end of the distro, was running at 120v.
 
Sounds like a harmonics issue..... Were they all FF ballasts? Prob getting bad return on neutral. Next time plug in a tungsten light as ghost load and it should take care of it.......
 
jpmcabe said:
Sounds like a harmonics issue..... Were they all FF ballasts? Prob getting bad return on neutral. Next time plug in a tungsten light as ghost load and it should take care of it.......
Click to expand...


Interesting... They were all FF ARRI ballasts. We did just end up replacing the 575 with a mickey and the 1.2 with a 5k.
 
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