When sizing a transformer, I was always under the assumption that you have to consider the worst case simultaneous loads.
I have a mixture of solenoids and fractional motors that I need to power from the secondary of my transformer. At worst case I have a couple contactors, air circulating motors, and refrigeration solenoids activating simultaneously. Then, a few minutes later I have more contactors and solenoids that will be activated.
The manual says that I allot 60VA to each of the solenoids for pickup, and 10W for holding. My motors are 2.6A each (2 air circ motors total), and my contactors have 67W pickup with 10W holding.
With the initial activation of my equipment, 2 air circ motors (whose FLA I will multiply by 1.25), 2 contactors (activating compressors not on the secondary), and 1 solenoid are energized. At 110V (secondary voltage) this comes up to 909VA using the 1.25 X's air circs, and the pickup VA for the contactors and solenoids.
Am I then able to drop back down to the holding VA's for the solenoids and contactors, and remove the 1.25 X's for the air circs when I calculate the rest of the loads? This would give me 602VA. Then, when more solenoids are activated in the system I would add the pickup VA's to the 602VA. Does this sound correct?
I would need to find my worst case inrush, and then my worst case full load, but I do not have to keep that initial inrush calculation throughout my entire calculation?
I have a mixture of solenoids and fractional motors that I need to power from the secondary of my transformer. At worst case I have a couple contactors, air circulating motors, and refrigeration solenoids activating simultaneously. Then, a few minutes later I have more contactors and solenoids that will be activated.
The manual says that I allot 60VA to each of the solenoids for pickup, and 10W for holding. My motors are 2.6A each (2 air circ motors total), and my contactors have 67W pickup with 10W holding.
With the initial activation of my equipment, 2 air circ motors (whose FLA I will multiply by 1.25), 2 contactors (activating compressors not on the secondary), and 1 solenoid are energized. At 110V (secondary voltage) this comes up to 909VA using the 1.25 X's air circs, and the pickup VA for the contactors and solenoids.
Am I then able to drop back down to the holding VA's for the solenoids and contactors, and remove the 1.25 X's for the air circs when I calculate the rest of the loads? This would give me 602VA. Then, when more solenoids are activated in the system I would add the pickup VA's to the 602VA. Does this sound correct?
I would need to find my worst case inrush, and then my worst case full load, but I do not have to keep that initial inrush calculation throughout my entire calculation?