svetz
Works in theory! Practice? That's something else
The label on the side of the AC condenser should state LRA (Locked Rotor Amps), for example a 3 ton AC might be 77, a 5 ton 145.
If LRA is the inrush, than 77A x 240V = 18.5 kVA would be needed. If the power factor is 1, that's 18.5 kW. For sizing a generator, this ref says:
So, for the generator it's probably taking 77 x .7 x (240x.7) = 13VA. I wonder at what appliance voltage sag the inverter resets at? A 30% dip is 168V, a 15% dip 204V. Possibly this can be calculated or deduced/calculated from the surge information?
Soft Start Candidate?
I've "heard" a soft starter can reduce the start up load by as much as 40%. How much of that is real and how do you pick a soft starter?
If LRA is the inrush, than 77A x 240V = 18.5 kVA would be needed. If the power factor is 1, that's 18.5 kW. For sizing a generator, this ref says:
The case is that nameplate LRA is given for full voltage starting. In reality, when you start a motor from a generator, the current surge causes voltage dip. When voltage drops, the current is reduced proportionally. Most residential appliances can start with 30% voltage sag, that is at 30% lower currents. As the result, starting volt-amps could be 0.7*0.7=0.49 of nominal.
For example, a typical 5-ton (5HP) a/c has 145 LR amps at 240VAC. At 30% voltage dip it would require (145*0.7)*(240*0.7)=17,052 VA to start. Note that commercial applications normally allow only 15% drop, in which case you would need to deal with 0.85*0.85=.72 of nominal starting kVA.
So, for the generator it's probably taking 77 x .7 x (240x.7) = 13VA. I wonder at what appliance voltage sag the inverter resets at? A 30% dip is 168V, a 15% dip 204V. Possibly this can be calculated or deduced/calculated from the surge information?
Soft Start Candidate?
I've "heard" a soft starter can reduce the start up load by as much as 40%. How much of that is real and how do you pick a soft starter?
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