What is transformer voltage?
A series transformer’s voltage is not fixed. With the current held constant by the CCR, the voltage across each transformer follows its load, and the voltages along the loop add up to what the CCR must supply.
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Transformer voltage is the voltage across a series isolation transformer. The CCR holds the loop current constant, so the voltage is not fixed: it follows the load. Roughly, voltage = power ÷ current, so a 45 W fitting at 6.6 A has about 6.8 V across its secondary, and on a 1:1 unit the primary drops a similar amount, a little more for the transformer’s own losses (about a third as much on a 20 : 6.6 A unit).
Every primary is in series, so the voltages add along the loop. The CCR must supply the sum of all the primary drops plus the voltage lost in the cable, which on a long circuit can reach thousands of volts even though each transformer only sees a few. Brightness is set by the loop current, not the voltage. Because the loop is high voltage, treat every primary and secondary lead as live and isolate and make the circuit safe under site procedures before any work.
Frequently Asked Questions
Q1What is transformer voltage in AGL?
The voltage across a series isolation transformer’s windings. The CCR holds the loop current constant, so this voltage is not fixed: it follows the load the transformer supplies, and, on a 1:1 unit, the primary drop is close to the secondary voltage plus a little for losses.
Q2Why does the voltage change when the current is constant?
Voltage is roughly power divided by current. With the current held constant by the CCR, a higher-power fitting has a higher voltage across its secondary and a lower-power one has less. For example, 45 W at 6.6 A is about 6.8 V.
Q3How do the voltages along the loop add up?
Every transformer’s primary is in series, so the CCR must supply the sum of all the primary drops plus the voltage lost in the cable. A long circuit with many lights can reach thousands of volts, even though each transformer only sees a few volts.
Q4Does voltage set how bright the lights are?
No. Brightness is set by the loop current, which the CCR changes in steps. The voltage follows from that current and the load.
Q5Why is the circuit hazardous if each fitting runs at a few volts?
Because the loop as a whole carries a high voltage, and the primary leads, connectors and cable are insulated for it. An open secondary can also show a higher voltage than normal. Treat every lead as live and isolate the circuit under site procedures before work.
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