What is series circuit voltage?
The voltage a CCR applies across the whole loop — the same current everywhere, with each load and the cable dropping their share.
Series circuit voltage is the voltage the CCR applies across the whole loop. In a series circuit the same current flows through every load, so each transformer, fixture and length of cable drops its own share of voltage, equal to the current times its impedance. The shares add up to the CCR output voltage.
Because the CCR holds the current fixed, the voltage is the quantity that changes: it rises when fixtures or cable are added and with each higher brightness step. Both the current and the voltage on the loop are dangerous: several amperes is far above a lethal current and the voltage can be high, so the circuit must be isolated before work. The impedance that sets the voltage is covered under circuit impedance.
- Fix the current. Take the current of the brightness step being checked.
- Find each drop. Multiply the current by the impedance of each transformer, fixture and cable section.
- Add them up. The sum of all the drops is the CCR output voltage (strictly a phasor sum for AC, so a plain addition is an estimate).
- Check the CCR. Confirm the voltage, and the resulting kW load, are within the CCR rating.
- Check the cable. Confirm the cable and joints are insulated for that voltage.
- Use the top step. Repeat at the highest current, where the voltage is greatest.
Frequently Asked Questions
Q1What is series circuit voltage?
The voltage the CCR applies across the whole loop. It equals the sum of the voltage drops across every load and every length of cable on the circuit.
Q2Why is the current the same everywhere but the voltage different?
A series circuit is a single path, so one current flows through every part of it. Each load and cable section drops a voltage equal to that current times its own impedance, so the drops differ even though the current does not.
Q3What sets the CCR output voltage?
The circuit current multiplied by the total circuit impedance. Adding fixtures or cable raises the impedance, so the CCR has to supply a higher voltage to hold the same current.
Q4Why does the voltage change with the brightness step?
Each brightness step is a different fixed current, and the loop voltage follows the load at that step. The top step normally needs the highest voltage, so the CCR must be able to supply it.
Q5Is the voltage on a series circuit dangerous?
Yes, and so is the current. The loop carries several amperes, far above a lethal current, and the CCR output voltage can be high, which is why the cable is insulated for it. Always isolate and lock out the circuit and follow the site safety procedure before working on it.
Q6What happens to the voltage if the loop opens?
The CCR keeps trying to push its set current through a break, so the voltage rises until its open-circuit protection normally shuts it down. This is why a broken loop is treated as a hazard as well as a lighting fault.
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