UPMSP High School Solar Repair flashcards

32 cards. Read the term and the definition here. The deck at the top of this page is optional.

Standard Test Conditions

Irradiance 1000 W/m², cell temperature 25 °C, and AM 1.5 spectrum. Nameplate power, voltage, and current ratings are measured here, so real-world output differs with temperature and irradiance.

Maximum power point

The point on a module's I-V curve where voltage times current is greatest. MPPT controllers track this point continuously as irradiance and temperature change through the day.

Bypass diode function

A diode across a module substring that conducts when that substring is shaded, allowing current to bypass it. This limits hot-spot heating and preserves the rest of the string's output.

Fill factor

The ratio of maximum power to the product of open-circuit voltage and short-circuit current. A squarer I-V curve gives a higher fill factor, typically 0.75–0.82 for crystalline silicon.

Temperature coefficient of power

The percentage change in maximum power per degree Celsius of cell temperature. For crystalline silicon it is roughly −0.35 to −0.45 %/°C, so hot modules produce less power.

Absorption charge stage

A constant-voltage stage at the elevated absorption setpoint, during which charge current tapers as the battery fills. It restores most capacity before the controller drops to float voltage.

Depth of discharge

The fraction of a battery's capacity removed during discharge. Deeper discharges shorten lead-acid cycle life sharply, so systems are usually sized to limit DoD to about 50 %.

MPPT controller

A DC-DC converter that continuously adjusts the array operating voltage to its maximum power point, then converts the surplus voltage into extra charge current for the battery.

Anti-islanding protection

A grid-tied inverter function that detects loss of grid supply and shuts down within the required time, preventing the inverter from energising a dead grid during utility work.

Pure sine wave inverter

An inverter producing a smooth sinusoidal AC output. It runs motors, chargers, and sensitive electronics correctly, unlike modified sine wave units that can cause overheating and buzzing.

Voltage drop formula

V_drop = 2 × L × I × ρ / A for a two-wire run, where L is one-way length, ρ is resistivity (copper ≈ 0.0175 Ω·mm²/m), and A is cross-sectional area.

String fuse rating

The fuse protecting a PV string is typically 1.25 × short-circuit current, and must not exceed the module's maximum series fuse rating. It protects cables, not the modules.

Equipotential bonding

Connecting module frames, rails, and equipment chassis to a common earth electrode so all metalwork sits at the same potential, preventing shock and enabling fault-current paths.

Shading survey

A site assessment using a sun-path tool or app to map obstructions across the year. It determines whether trees, chimneys, or cables will shade the array in critical months.

Module tilt rule of thumb

For year-round yield in the tropics, tilt roughly latitude minus 10°. Steeper tilts favour winter production; flatter tilts favour summer and reduce dust accumulation.

Insulation resistance test

A megger test applying 500 V or 1000 V DC between array conductors and earth. A healthy array reads above 1 MΩ; low readings indicate water ingress or cable damage.

I-V curve tracing

A field test plotting current against voltage across the array's operating range. Steps or knees reveal shaded or failed substrings; comparing to the datasheet at measured conditions quantifies degradation.

Open-circuit voltage test

Measuring string voltage with no load and comparing to the temperature-corrected sum of module V_oc values. A low reading indicates a broken series link or failed bypass diode.

Thermal imaging inspection

Using an infrared camera to find hot spots, failed bypass diodes, loose terminations, and cell cracks. Temperature anomalies reveal faults that a voltmeter alone cannot detect.

Performance ratio

Actual energy output divided by the energy the array would produce at its rated power under the measured irradiance. A sudden drop above 10 % signals a fault.

Soiling loss

The reduction in output caused by dust, pollen, bird droppings, or salt on the glass. Cleaning restores yield; frequent cleaning is needed at dusty or coastal sites.

Snail trails

Discoloured lines along cell fingers caused by encapsulant degradation and silver paste reaction. They are a warranty-relevant degradation sign and can reduce yield.

CAT III meter rating

A safety rating for test instruments used on distribution-level circuits. A 1000 V DC array requires a meter rated at least 1000 V DC on the applicable range.

Lockout tagout

Isolating AC and DC supplies, locking the isolator, tagging it, and verifying absence of voltage before work. The tester is proved on a known live source before and after.

Hydrogen hazard

Flooded lead-acid batteries release hydrogen while charging. Ventilate the battery room and avoid sparks, flames, or smoking near the bank to prevent explosion.

Solar home system sizing

Daily appliance watt-hours divided by system voltage and depth of discharge gives battery amp-hours. Array watts equal daily watt-hours divided by peak sun hours and derating.

Dry-run protection

A pump controller feature that stops the pump when the water source runs dry, preventing motor overheating and damage. Essential for solar water pumping systems.

Solar lantern battery

Most solar lanterns use LiFePO₄ or lithium-ion cells with an integrated controller. Usable watt-hours, not nominal capacity, determine the actual runtime promised to users.

Inverter surge rating

The short-term power an inverter can deliver, often twice its continuous rating for a few seconds. It must exceed the starting surge of motor loads such as fridges and pumps.

Blocking diode

A series diode that prevents reverse current from flowing into a weaker parallel string or from the battery back into the array at night, protecting modules from damage.

Float charge

A lower constant voltage applied after absorption to maintain a fully charged battery while compensating for self-discharge, without causing gassing or overcharge.

Earth continuity test

A low-resistance measurement between metalwork and the earth electrode, confirming the bonding path is intact. High resistance means a shock hazard under fault conditions.