No, higher voltage by itself does not necessarily mean more power. The relationship between voltage and power is complex and varies depending on the operating context. Even if the voltage is high, the power can be low.
So, let’s look closer to understand the complexity behind the relationship between voltage and power.
Relationship Between Voltage and Power
The fundamental relationship between voltage, current, and power is:
Power (P) = Voltage (V) x Current (I)
So at first glance, it is obvious that increasing voltage will increase power.
For example, a circuit with voltage is 10 volts and current is 5 amps –
Power = 10 x 5 = 50 Watts
Increasing the voltage to 20 V while keeping the current at 5 A –
Power = 20 x 5 = 100 Watts
However, this assumes current stays constant, which may not always be true in real systems.
AC Power System | Voltage-Power Relation
In AC power systems, current and voltage can be out of phase by a phase angle (φ). Power depends on this phase angle according to the power equation:
Power (P) = Voltage (V) x Current (I) x Cos(φ)
Let’s say we have a circuit with:
Voltage (V) = 10 volts
Current (I) = 5 amps
Phase angle (φ) = 30 degrees
Using the power formula:
P = VIcosφ
= 10 x 5 x cos(30)
= 50 x 0.866
= 43.3 watts
Now if we double the Voltage (V) = 15 volts
Current (I) = 5 amps
But Phase angle (φ) = 60 degrees. So,
P = 15 x 5 x cos(60)
= 75 x 0.5
= 37.5 watts
So, even if voltage is increased, power will decrease if the phase angle increases or power factor decreases.
When voltage is increased, it can affect the current flowing through the circuit, especially in cases involving reactive components like inductors and capacitors. If the current lags behind the voltage, it can result in a larger phase angle and, consequently, a lower power factor.
Exceptions When Increasing Voltage Decreases Power
In practical scenarios, simply ratcheting up the voltage can decrease usable power under certain conditions because real components have nonlinearities, saturation effects, and limits that cause the current to change disproportionately with increasing voltage.
1. Fixed Resistive Loads
For fixed resistive loads, V=IR according to Ohm’s law. However, power depends on the square of current, P=I2R .
This is because real systems have inherent resistive losses that consume some of the power. At higher currents, these nonlinear losses become more significant.
2. Current-Limiting or Regulation
Power supplies and voltage regulation systems often employ current-limiting circuits. These circuits monitor the output current and actively limit or clamp it to a preset maximum level when exceeded.
Upon hitting the current limit threshold, further increases in voltage no longer result in corresponding current increases. The current stays clamped at the maximum level while the voltage continues increasing. Thus, it decreases power.
3. Magnetic Core Saturation
Magnetic materials have a linear voltage-flux relationship until saturation. Beyond that point, increased voltage doesn’t yield proportional flux increase. Doubling voltage in transformers or motors can saturate the core, wasting voltage across resistance and leakage reactance, elevating reactive power and reducing real power.
4. Arcing and Breakdown
At higher voltages, arcing can occur in commutator motors. As voltage rises across an air gap or dielectric, electric field intensity increases proportionally until reaching breakdown voltage.
Arcing suddenly happens, creating a low-resistance path where current spikes but voltage drops due to the arc’s high conductivity. This leads to a power surge dissipated as heat and light in the arc, wasting excess power that could have been utilized.
5. Waveform distortion
Inverters and converters utilize switching elements for generating AC or DC outputs. High input voltage can cause slow response in switching, leading to misfiring, uneven delays, and output spikes. These distortions with higher harmonics reduce useful power transfer, impacting load efficiency.
Frequently Asked Questions (FAQs)
1. How Does Voltage Affect the Power Factor??
Answer: Excessive voltage can saturate cores, increasing reactive power and worsening the power factor. Capacitors may be needed to correct it.
2. Can Transformers be Damaged by Excessive Input Voltage?
Answer: Yes, overvoltage can cause insulation breakdown and windings overheating due to abnormally high magnetizing currents.
3. How to Maximize Power for an Application?
Answer: By carefully selecting voltage and current ranges based on component ratings and operating conditions. Stay within linear regions of magnetic materials. Minimize resistive and switching losses.
While increasing voltage does increase power, real-world non-idealities require a deeper look. The overall power outcome depends greatly on the operating context and components involved. When attempting to maximize power, one must consider both the voltage and current effects particular to each unique system.
Subscribe to our newsletter
& plug into
the world of circuits