Voltage drop

Voltage drop is a reduction in voltage in an electrical circuit between the source and the load. Put more simply, voltage drop is when the voltage at the end of a run of cable is lower than it is at the beginning. Regardless of length, all wires have some degree of resistance, or impedance. Running an electrical current through this impedance will inevitably lead to a decrease in voltage. Voltage drop, then, can be described as the amount of voltage loss that occurs through a circuit as a result of impedance. Functionally, voltage drop can cause the load to operate less efficiently because less voltage is available to drive the current. Depending on what is being powered, excessive voltage drop may result in flickering lights, poorly functioning heating elements, or overheating of electrical motors. In the worst-case scenarios, excessive voltage drop can even spark an electrical fire.

Background

Voltage drop is an issue related to electricity and the flow of electrical current through a circuit. As such, there are a number of key terms and concepts with which it is necessary to be familiar in order to properly understand voltage drop. Some of these important terms and concepts include circuits, current, and voltage.

A circuit is a closed loop of conductors through which current can travel. In a circuit, electrons flow through a conductor, such as a copper wire. The electrons that flow through a circuit are supplied by an energy source. One example of an energy source that might power a given circuit is a battery. A circuit allows for the transmission of electrical energy when it forms a closed, conducting loop. This happens when the circuit’s switch is moved to the “ON,” or closed, position. When the switch is moved to the “OFF,” or open position, the flow of electricity stops. If a device such as a lamp is attached to a circuit, it will receive power and turn on when the circuit is closed and turn off when the circuit is open, and its supply of electricity is terminated.

In relation to electricity and electrical circuits, the term current refers to the rate at which electrons flow past a given point in a complete circuit. Current is measured using a unit called an ampere, or amps. An ampere measures the rate of electric charge flowing past a given point in a circuit. There are two types of current: direct (DC) and alternating (AC). The main difference between DC and AC is in the way each type of current flows. DC flows in only one direction. The most common sources of DC are batteries and DC generators. AC commonly flows in a sine wave pattern and reverses direction at regular intervals. The most common sources of AC are the public utility-powered electrical outlets found in most homes and other buildings.

Voltage is the electrical potential difference supplied by the power source connected to a circuit. This pressure pushes a current of charged electrons through the circuit, thereby enabling the flow of electricity from a power source to any electrical device attached to the circuit.

Overview

Voltage drop is a loss of voltage in an electrical circuit that arises as a result of impedance to the flow of current. One of the easiest ways to understand the problem of voltage drop is to think of water flowing through a garden hose as an analogy for electrical current flowing through a circuit. When the hose is attached to a spigot that is turned on all the way, pressurized water flows through the hose at full blast. However, if the hose has a few tears along its length, a problem akin to voltage drop is likely to occur. At each tear in the hose, some water escapes, and the water pressure is reduced. As a result, the overall pressure of the water is lower at the end of the hose than it is at the beginning. To reframe that analogy in the context of electric current flowing through a circuit, one might imagine a typical string of Christmas tree lights. At the beginning of the string, where the plug is inserted into the electrical outlet, current flows at its full voltage. As the current passes through the circuit, a small amount of voltage is drained by each light in the string. By the time the current reaches the last light in the string, enough voltage has been drained, and the last light is a little dimmer than the rest. The slightly dimmer glow of the last light in the string is a direct result of voltage drop.

There are many potential causes of voltage drop. In some cases, voltage drop may be tied to the type of wiring used in a circuit. Some materials are more conductive than others. As a result, voltage drop may be more likely to occur depending on what type of material is used for the wiring of a circuit. For example, aluminum is less conductive than copper and is therefore more likely to cause some degree of voltage drop when it is used in a circuit. Wire size and length can also factor into voltage drop. In wires of the same length, a wire that is larger in diameter will exhibit less voltage drop than a wire that is smaller in diameter. Shorter wires also exhibit less voltage drop than longer wires. Voltage drop can even be related to the current flowing through a circuit. Voltage drop typically increases as the amount of current flowing through the circuit increases. Excessive voltage drop can be caused by poor splices, loose connections, corroded connections, the use of wiring that does not meet code standards, and other issues. Voltage drop has become increasingly important in EV charging installations because these systems often involve long conductor runs and sustained high-current loads.

Voltage drop can have a number of consequences. It may result in low voltage to any devices being powered, poor efficiency, wasted energy, and overheating that can lead to a fire. There are also some ways to prevent or fix voltage drop. These methods include shortening wire length, using thicker wires, or distributing the electrical load more effectively.

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