Voltage drop is a phenomenon that occurs when electric current flows through a conductor, such as a wire or circuit component. It is a measure of the loss of electrical potential energy as the current flows through the conductor and is a common problem in electrical systems.

Voltage Drop Calculator

What is voltage drop?

Voltage drop is the difference between the voltage at the source of an electric current and the voltage at the load or destination. It is a measure of the loss of electrical potential energy as the current flows through the conductor.

For example:

Suppose we have a circuit with a voltage of 120 volts at the source and a load that requires 100 volts to operate. If the circuit has a resistance of 10 ohms, the voltage drop across the circuit will be 20 volts

(120 volt – 100 volt = 20 volts)

This means that the voltage at the load will be 100 volts, rather than the full 120 volts supplied by the source.

Voltage drop is a common problem in electrical systems, as it can reduce the power available to operate electrical devices and cause them to malfunction or fail. It is important to understand and account for voltage drop in order to design and maintain reliable and efficient electrical systems.

PDFs / Technicals

Voltage Drop Calculations (PDF)

Voltage Drop Technical Explanations (PDF)

Eaton, Bussmann Official Voltage Drop Calculation Charts (PDF)

Why does voltage drop occur?

Voltage drop occurs due to the resistance of the conductor through which the electric current flows.

When electric current flows through a conductor, it encounters resistance, which converts some of the electrical potential energy into heat. This reduces the voltage at the load, causing a voltage drop.

The amount of voltage drop depends on the resistance of the conductor and the amount of current flowing through it. The higher the resistance or the current, the greater the voltage drop will be. This means that voltage drop is more likely to occur in circuits with high resistance or high current.

How to calculate voltage drop

Voltage drop can be calculated using Ohm’s law, which states that the electric current flowing through a conductor is directly proportional to the voltage applied across it, provided the temperature and other physical conditions remain constant. This can be mathematically expressed as:

I = V/R

Where I is the electric current (measured in amperes), V is the voltage (measured in volts), and R is the resistance (measured in ohms).

To calculate the voltage drop in a circuit, we can rearrange this equation to solve for V, as follows:

V = IR

Where I is the electric current flowing through the circuit, R is the resistance of the conductor, and V is the voltage drop.

For example:

Suppose we have a circuit with a resistance of 10 ohms and a current of 5 amperes. Using Ohm’s law, we can calculate the voltage drop as follows:

V = IR = 5 amperes * 10 ohms = 50 volts

This tells us that the voltage drop in this circuit is 50 volts.

Formulas By Type:

Factors that Impact Voltage Drop

The voltage drop in a circuit depends on several factors, including the type of conductor, the wire gauge, the wire length, the supply voltage, and the load rating. To calculate the voltage drop, we need to consider these factors and apply the appropriate formulas:

1. The type of conductor affects the resistance of the circuit and therefore the voltage drop. Different types of conductors, such as copper, aluminum, and steel, have different resistivities, which determine their resistance to electric current. The lower the resistivity of the conductor, the lower the resistance and the voltage drop will be.
   
2. The wire gauge affects the resistance of the circuit and therefore the voltage drop. Larger-gauge wires have lower resistance than smaller-gauge wires, so they are less likely to cause voltage drop. For example, a 12-gauge wire has less resistance than a 14-gauge wire, so it is less likely to cause voltage drop.
   
3. The wire length affects the resistance of the circuit and therefore the voltage drop. The longer the wire, the greater the resistance and the voltage drop will be. Therefore, it is important to keep the distance between the source and the load as short as possible to minimize voltage drop.
   
4. The supply voltage affects the voltage drop in the circuit. The higher the supply voltage, the greater the voltage drop will be for a given resistance and current. Therefore, it is important to use a supply voltage that is appropriate for the circuit and the load.
   
5. The load rating affects the voltage drop in the circuit. The higher the load rating, the greater the current flowing through the circuit and the greater the voltage drop will be for a given resistance. Therefore, it is important to use a load that is appropriate for the circuit and the supply voltage.

To calculate the voltage drop in a circuit, we need to consider these factors and apply the appropriate formulas.

For example:

suppose we have a circuit with a copper conductor, a 12-gauge wire, a wire length of 100 feet, a supply voltage of 120 volt, and a load rating of 100 watt. The resistance of the copper conductor is 0.0125 ohms/foot, and the resistance of the 12-gauge wire is 0.005 ohms/foot. The current flowing through the circuit is 0.83 amperes (100 watt / 120 volt = 0.83 amperes).

The total resistance of the circuit can be calculated as follows:

R = (0.0125 ohms/foot * 100 feet) + (0.005 ohms/foot * 100 feet) = 1.25 ohms + 0.5 ohms = 1.75 ohms

The voltage drop in the circuit can be calculated using Ohm’s law as follows:

V = IR = 0.83 amperes * 1.75 ohms = 1.45 volts

This tells us that the voltage drop in this circuit is 1.45 volts.

It is important to note that the actual voltage drop may be different from the calculated value

Depending on the specific arrangement and configuration of the circuit components. Therefore, it is necessary to calculate the voltage drop for each individual circuit in order to determine the voltage at the load.

Preventing and minimizing voltage drop

• Voltage drop can be prevented or minimized by reducing the resistance of the conductor through which the electric current flows. This can be achieved by using wires or other conductors with low resistance, such as copper or aluminum.

• voltage drop can be minimized by keeping the distance between the source and the load as short as possible. This reduces the length of the conductor and thus the resistance of the circuit. Furthermore, voltage drop can be minimized by using larger gauge.

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