Victron Energy ITR000100001 Isolation transformer 1 x 120 V, 240 V 1 x 120 V, 240 V 32 A

An isolation transformer can be used for upward, downward and split phase output balancing purposes. While the up and down functions are fairly straightforward, the split phase output balance requires a little more attention.The autotransformer: For balancing up, down and split phasesAn autotransformer can be used to balance up, down and split phase outputs. While the up and down functions are quite simple, balancing the split phase output requires a little more attention.For example, a split phase supply of 30 A 120/240 V. The supply can be via the mains, a generator or two coupled inverters. Some of the connected loads require 240V, other 120V on each 120V circuit should not exceed 30A. The problem is that the two circuits have a different current as soon as 120 V loads are connected. The reason for this is that the 120 V loads on the two circuits will never be balanced. For example, a 120V 1200 W hair dryer pulls 10A off a circuit. A 120V washing machine can pull more than 20A from a circuit. The current difference between the two circuits, also known as current unbalance, is therefore often 20 A or more. This means that the 30 A supply is not fully utilized. As soon as one circuit pulls 30 A, the other circuit may not pull more than 10 A. Increasing the 240 V load, for example, will overload one circuit, while the other circuit will still have free capacity.Theoretically, the total power of a 30A and 120/240 V power supply is 30 x 240 = 7.2 kVA. In the case of an unbalance of 20 A, the practical maximum is 30 x 120 + 10 X120 = 4.8 kVA or 67% of the theoretical maximum.The solution is an autotransformer.If the neutral conductor of the split phase supply is left unused and an autotransformer is connected as a new neutral conductor, as shown in Figure 1, any unbalance of the load is "absorbed" by the autotransformer. In the case of a 30 A supply, the load can be increased to 7.2 kVA. A 20 amp unbalance of the load causes one circuit to supply 40 amps and the other 20 amps. The difference of 20 A flows through the neutral conductor and the coil of the autotransformer. The current through the two 120 V lines of the split phase supply is 30 A.Includes grounding relay for use with multi or Quattro inverters/chargersWhen operating in inverter mode, the neutral conductor of the inverter/charger must be connected to the ground in order to ensure the proper functioning of a GFCI. In the case of a split phase supply, the neutral conductor must be grounded. For this purpose, a grounding relay is installed in the housing of the autotransformer. The relay is controlled by the 230/240V Multi or Quattro. (The internal grounding relay of the 230/240 V Multi or Quattro must be deactivated)Temperature-protectedIn case of overheating, the autotransformer is disconnected from the power supply. The reset is done manually.An alternative to coupled invertersThe alternative to coupling two 120 V inverters for a 120/240 V split phase supply is a 240 V inverter with an additional autotransformer. Two stacked 120V 3kVA inverters deliver up to 25A to each 120V circuit. If the load on one circuit is less than 25 amps, the maximum load on the other circuit is still limited to 25 amps. A 5 kVA 240 V inverter with a 32 A autotransformer supplies each 120 V circuit with a balanced load of up to 21 A. However, fewer loads on one circuit will result in more current being available on the other circuit, with the maximum unbalance being 32 A. The load can therefore be up to 38.5 A on one circuit if the load on the other circuit is not more than 3.5 A (maximum unbalance: 38.5 / 3.5 / 35 A If an asymmetric load is to be expected, a 240 V inverter with lower power and an autotransformer is to be preferred to the solution with coupled inverters.

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