04-11-2019, 02:32 AM,
 ThermalSprayingPhysicist Member Posts: 9 Threads: 3 Joined: Jun 2015 Reputation: 0
Hi all,

I am an academic researcher who is trying to use thermal spray to develop new low density coatings for optics.

One way that I have been pushing the density down is by varying the following parameters: spray distance, powder feed rate, and secondary gas (He) pressure.

I have been reading literature that shows input power of the plasma. The literature says that they hold plasma current and voltage constant while they vary input power. The plasma spray technician has noted to me that input power is simply plasma current x voltage.

Who is right here? I am very confused. Thanks in advance for any help!

P.S. I've attached a screen shot of the paper.

Attached Files Thumbnail(s)

04-11-2019, 01:03 PM,
 Lemster68 Senior Member Posts: 56 Threads: 2 Joined: Jul 2018 Reputation: 1
RE: Fundamental Question about Input Power
Volts x amps = wattage: power. 600A x 50v =30000w -- 30kw.
04-11-2019, 01:06 PM,
RE: Fundamental Question about Input Power
Hi ThermalSprayingPhysicist

I would say your plasma spray technician is correct. Holding current, voltage and plasma gas flows constant will make power constant, unless they are measuring power in a different way

By having He secondary plasma gas as a variable, changing this value will change the power (the voltage will change assuming constant current). Changing spray distance and powder feed rate only should have no effect on power.

Hope that helps.

04-11-2019, 07:30 PM,
 ThermalSprayingPhysicist Member Posts: 9 Threads: 3 Joined: Jun 2015 Reputation: 0
RE: Fundamental Question about Input Power
(04-11-2019, 01:06 PM)Gordon Wrote: Hi ThermalSprayingPhysicist

I would say your plasma spray technician is correct. Holding current, voltage and plasma gas flows constant will make power constant, unless they are measuring power in a different way

By having He secondary plasma gas as a variable, changing this value will change the power (the voltage will change assuming constant current). Changing spray distance and powder feed rate only should have no effect on power.

Hope that helps.

So just to get the details correct, voltage (measured number like 50V) is determined by He secondary gas pressure? While current is not. So what are the independent variables: He gas pressure and current?

If this is true, I should be lowering both gas pressure + current.

04-11-2019, 08:23 PM,
 Lemster68 Senior Member Posts: 56 Threads: 2 Joined: Jul 2018 Reputation: 1
RE: Fundamental Question about Input Power
(04-11-2019, 07:30 PM)ThermalSprayingPhysicist Wrote:
(04-11-2019, 01:06 PM)Gordon Wrote: Hi ThermalSprayingPhysicist

I would say your plasma spray technician is correct. Holding current, voltage and plasma gas flows constant will make power constant, unless they are measuring power in a different way

By having He secondary plasma gas as a variable, changing this value will change the power (the voltage will change assuming constant current). Changing spray distance and powder feed rate only should have no effect on power.

Hope that helps.