size of generator

[Travelover]

The 140 amp draw is momentary. The largest draw is when they first turn it on in the morning. If the tubes cool down (anode and cathode ray) there is the momentary draw once more. Actual imagery is only a flea's worth of electricity at 300 Ma.

I wonder if a soft start device could be used on the XRay machine like is used on air conditioning units to spread the initial surge current over a few seconds.

 

[prichard]

Wonder if it's worth them looking at a new digital xray. May have less inrush and may pay back with lower cost generator and electric bills.

 

[SPYDERLK]

The 140 amp draw is momentary. The largest draw is when they first turn it on in the morning. If the tubes cool down (anode and cathode ray) there is the momentary draw once more. Actual imagery is only a flea's worth of electricity at 300 Ma.

I wonder if a soft start device could be used on the XRay machine like is used on air conditioning units to spread the initial surge current over a few seconds.

Yes. But I suspect that the heater surge is longer. Still, its the high surge level that is the problem for a genny, and it is almost definite that the level could be lowered significantly by appropriately spreading the time of the initial and subsequent short heater cycles.

... I would 1st get an electronics guy to look at the machine schematics and query the xray mfg knowledgably. Heaters are pretty simple, not rocket science, and softer usage would prevent the significant oversizing of the gen that is being proposed to cover the abusive uncontrolled surges.​

 

[buickanddeere]

The heaters all have to be on together and full output . There is no way to trim that 140amp peak.

 

[SPYDERLK]

The heaters all have to be on together and full output . There is no way to trim that 140amp peak.

Sure there is. ... Or, how do you think you know that assuredly?

 

[buickanddeere]

Sure there is. ... Or, how do you think you know that assuredly?

It's an over sized vacuum tube , the heaters all have to be on in order to source electrons. This is not a domestic water heater

 

[CobyRupert]

I'm still confused.
140A is momentary, but is it just a short cycle, or an inrush?

I suspect it is not inrush as this would be hard to measure and assign a value (like 140amps) to. (i.e. You would probably measure a steady state current of something else.)

Let's assume there is a short period of 140 amps as it quickly heats (i.e. longer than ~1/6 of a second). Then the question becomes: Is there also an associated inrush on top of that? (i.e. Are there windings like a motor would have (I imagine a MRI machine probably has); or does machine have a step-up transformer?)

Generator has to be sized for two things: Running load and inrush ((starting load). You have to know both components of what your load is.
If you have large inrush, the generator has to be (over)sized appropriately. It's not just load volts x amps = generator KW(KVA). Motor torque, governor response & generator saturation current limits then come into play.

It is my understanding that the torque response of a diesel motor powered generator enables it to respond better to inrush and it doesn't have to be oversized as much a a LP or natural gas motor would.

 

[KYErik]

Since it is just a momentary surge, any chance that a large capacitor bank could be installed? Sort of like the starting capacitor that helps provide the power to initially start a large AC electric motor. I'm not an expert in electricity, just thinking out loud.

 

[CobyRupert]

Since it is just a momentary surge, any chance that a large capacitor bank could be installed? Sort of like the starting capacitor that helps provide the power to initially start a large AC electric motor. I'm not an expert in electricity, just thinking out loud.

I might be wrong, but I don't think it's been defined what the "momentary surge" is.
If it's an inrush caused by magnetizing an inductive load (think coils, like a transformer or motor), than a capacitor bank can help counter (balance) this inductance.
If it's a resistive load (think heater) that's "momentary" only because it's a short cycle, then added capacitance doesn't help.

 

[SPYDERLK]

It's an over sized vacuum tube , the heaters all have to be on in order to source electrons. This is not a domestic water heater

These are incandescent heaters. Inrush to a 100W bulb is 13A, dropping to 0.8A as the filament heats -- a 16 fold drop. While the cathode heaters in the xray vacuum tube may not exhibit this phenom to such extent, they will exhibit it. Even a 2 fold drop opens all kinds of possibilities.

Since it is just a momentary surge, any chance that a large capacitor bank could be installed? Sort of like the starting capacitor that helps provide the power to initially start a large AC electric motor. I'm not an expert in electricity, just thinking out loud.

This could certainly work. ... More straightforwardly if the heavy momentary can be fed directly by the DC that capacitors store and release so well.

I might be wrong, but I don't think it's been defined what the "momentary surge" is.
If it's an inrush caused by magnetizing an inductive load (think coils, like a transformer or motor), than a capacitor bank can help counter (balance) this inductance.
If it's a resistive load (think heater) that's "momentary" only because it's a short cycle, then added capacitance doesn't help.

Capacitance can be arranged to help either way, but it could become complicated - depending on what machine function is the culprit.