Generator for 69NT40-449

[Eugenio]

hi, a customer ask me about a generator (gasoline operated) to mantain a 69NT40-449 reefer operating when main supply falls.
Since motors starts sequentially, compressor motor has the main load, as manual says:
I = 17.6 A @ 460 VAC full load,
here 380 VAC, hence with cos fi = 0.8, y eta = 0.9
Pn = 1.73*380*0.8*0.9*17.6 = 10.7 kW or Sn = 14 kVA (approx.)
Now, in the start (DOL), this motor use 6*In, so I need a generator with 6*14 kVA = 84 kVA
Another motors do not modify the required power.
This power seems to be high.
Is my reasoning correct??
thanks in advance
Eugenio

[goshen]

hi, a customer ask me about a generator (gasoline operated) to mantain a 69NT40-449 reefer operating when main supply falls.
Since motors starts sequentially, compressor motor has the main load, as manual says:
I = 17.6 A @ 460 VAC full load,
here 380 VAC, hence with cos fi = 0.8, y eta = 0.9
Pn = 1.73*380*0.8*0.9*17.6 = 10.7 kW or Sn = 14 kVA (approx.)
Now, in the start (DOL), this motor use 6*In, so I need a generator with 6*14 kVA = 84 kVA
Another motors do not modify the required power.
This power seems to be high.
Is my reasoning correct??
thanks in advance
Eugenio
this is where soft starters come in handy !!
but a good generator should be able to handle a momentary start of a motor.
we started big screw compressores 185 hp on a generator but we did use soft starters it handeled perfectly.
good luck;)

[Frikkie]

Hello Eugenio,

I agree if your motor draws 17.6A run current then it will be approw an 18kW motor. To convert to KVA you need to know the power factor but 14 KVA sounds realistic. I woul specify a 30KVA generator to allow for starting and miscellaneous other fans etc.

[Eugenio]

Thanks goshen and Frikkie for your answers
From Carrier manual 17.6 A @ 460 VA full load => 10 kW = 14 kVA@380 VAC
Istar = 6 x 17.6 A = 105.6 A, so 6 x 14 kVA = 84 kVA, really great
Reading and searching here and there, I found generators support 300 % I nominal during 10 sec,
and 2 or 3 nominal power.
By other side I measured 15 A, corresponding to 11.4 kVA.
Joining these concepts, generator power should be
11.4 kVA x 2 = 22.8 kVA
11.4 kVA x 3 = 34.2 kVA
I consulted Carrier and they sell 19 kVA generator for this reefer. Not so far from my 22.8 kVA !!
I guess your advice about using 30 kVA is right too, because customer has several lights and PCs (with UPS)
to load to generator when main supply go down. Eugenio

[housefull]

Any one?


To be continued....