Power Factor

Understanding Power Factor

Power factor is a critical but often overlooked aspect of LED wall electrical planning. Understanding it prevents undersized circuits and unexpected issues.

Power Factor Explained

**Definition:** The ratio of real power (useful work) to apparent power (total power drawn).

PF = Real Power (W) ÷ Apparent Power (VA)

**Perfect PF = 1.0:** All power does useful work (purely resistive load).

**Lower PF < 1.0:** Some power is "wasted" as reactive power.

Types of Power

**Real Power (Watts):**

• Does actual work
• Powers the LEDs
• What you pay for (usually)

**Reactive Power (VARs):**

• Oscillates between source and load
• Does not do useful work
• Still requires current capacity

**Apparent Power (VA):**

• Total power the circuit must carry
• VA = Volts × Amps
• What determines wire/breaker sizing

Why LED Loads Have Low PF

**Switching Power Supplies:** LED panels use switch-mode power supplies that:

• Draw current in pulses
• Create harmonic distortion
• Cause current to lead or lag voltage

**Without PFC:** Basic supplies may have PF of 0.6-0.7.

**With PFC:** Quality supplies achieve PF of 0.9-0.95+.

Impact on Calculations

**Simple Calculation (Ignoring PF):** Amps = Watts ÷ Volts 10,000W ÷ 208V = 48.1A

**Correct Calculation (With PF = 0.9):** Amps = Watts ÷ (Volts × PF) 10,000W ÷ (208V × 0.9) = 53.4A

**Difference:** 11% more current than simple calculation.

Practical Implications

**Wire Sizing:** Must handle actual (apparent) current, not just calculated real power current.

**Breaker Capacity:** Breakers trip on current, not power—must account for power factor.

**Generator Sizing:** Generators rated in kVA, not kW—power factor matters.

**Utility Bills:** Some utilities charge PF penalties below 0.85.

Harmonic Distortion

**Related Issue:** LED power supplies also create harmonics:

• Non-sinusoidal current draw
• Third harmonics add on neutral
• May require oversized neutral conductor

**Symptoms:**

• Warm neutral conductors
• Interference with other equipment
• Transformer heating

Improving Power Factor

**Quality Power Supplies:** Specify panels with high PF (0.95+).

**Power Factor Correction:** External PFC equipment can be added but is rarely practical for LED walls.

**Proper Sizing:** Account for PF in all calculations—cheaper than adding equipment.

Specification Checklist

**What to Check:**

• Power factor specification (target: >0.9)
• THD (Total Harmonic Distortion) specification
• Whether specifications are at full load or partial load

**Red Flags:**

• No PF specification listed
• PF below 0.85
• No mention of PFC circuits

Generator Considerations

**Generators and PF:**

• Rated in kVA (apparent power)
• Actual kW capacity = kVA × PF
• LED loads may require larger generator than kW suggests

**Example:**

• LED wall: 20kW real power
• Power factor: 0.9
• Apparent power: 22.2kVA
• Generator: Size for 25kVA minimum