Aviation ground power units. Continuous load?

[chris kennedy]

I have a Hobart GPU-400 that the name plate states 56A at 208 3?. Customer wants this cord and plug connected so he can move it from hanger to hanger. I want to use a L15-60R and P.

I'm assuming 2 things here;
1) Name plate has continuous figured in if applicable
2) If the above is incorrect, input amps would never see 56 for three hours.

Link to specs.

Thanks

 

[skeshesh]

Chris, why not a quick call to the mfg?

 

[chris kennedy]

After hours now, but on the list of things to do tomorrow. Another question I'm directing to them is if they allow this to be cord and plug connected. Input side has a 100' 6/4 PPC/TPE cord so again I'm guessing yes.

 

[skeshesh]

I see. Well for what it's worth I agree with what you stated but hearing it from the horse's mouth is always well-advised.

 

[chris kennedy]

I see. Well for what it's worth I agree with what you stated but hearing it from the horse's mouth is always well-advised.

Agreed, but given the wealth of knowledge around here I never hesitate to throw it out there.

 

[hillbilly1]

I always use a 60 or 100 amp pin and sleeve plug on those, it costs more, and is heavy duty, but not bullet proof, I replaced one that was yanked off the wall when a Mercedes braked while on top of the cord. Just happened to be standing there when it happened. I was waiting to board the plane it was attached to! Here they use short sections of pvc over the cord to protect it, while still allowing flexibility.

 

[suemarkp]

I would think the input load would mirror what is connected to the GPU. Plug in a 747, and it will suck everything it has. So the next question, is are these GPU's generally connected for 3 hours or more. I would think not, but don't know enough about how most aircraft are used when they only fly a few times per day.

I would think you could get away with a non continuous use since planes are a different size (none may use all the power you have in the GPU), and generally won't be sitting on these for 3 hours at their full load.

Most around here also use the pin and sleeve receptacles.

 

[broadgage]

The maximum continous output of the ground power unit is stated to be 400 amps at 28.5 volts, that is about 11.4KW.
Assuming a pessimistic efficiency of about 80%, that would be a power input of about 14.3 KW.
That is a lot less than the stated input of 56 amps per phase at 3 phase 208 volts.

The maximum input current is presumably short term for engine starting, not a continous draw.
Therefore size the circuit for 56 amps as per the instructions. No need to allow for a continous load, since the 56 amps can only be used briefly, with the continous load being very much less.

 

[Twoskinsoneman]

The maximum continous output of the ground power unit is stated to be 400 amps at 28.5 volts, that is about 11.4KW.
Assuming a pessimistic efficiency of about 80%, that would be a power input of about 14.3 KW.
That is a lot less than the stated input of 56 amps per phase at 3 phase 208 volts.

The maximum input current is presumably short term for engine starting, not a continous draw.
Therefore size the circuit for 56 amps as per the instructions. No need to allow for a continous load, since the 56 amps can only be used briefly, with the continous load being very much less.

I agree with this statement. Size per 56a since it appears this is the max peak for engine starting. Certainly not continuous.

 

[suemarkp]

The amps could be higher than you expect because of power factor.

 

[broadgage]

The amps could be higher than you expect because of power factor.

True, but probably not by that much.
It is said to be switched mode, which in large sizes normally has a good power factor.
And the maximum input of 56 amps is in engine starting mode, the continous output is much less, therefore the continous input current would be a lot less.