Glossary: T

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Transformer: A device that raises or lowers the voltage of an alternating current electrical source.


The part of a wind generator that makes the rotor face into the wind. Often the tail is also involved in governing the machine, by folding down or sideways to swing the rotor out of the wind.


The pipe, flume, or channel in a hydroelectric system that carries the water from the turbine runner back to the stream or river.

Temperature Compensation

Adjustment of the rectifier output voltage to provide the optimum charging voltage for the battery. One of the components in system voltage control, calculated by the Supervisory Module calculation based on battery temperature.

Temperature Sensor

A sensor that is used to produce a variable electrical output representing the temperature of a component, typically a battery.


A connector for attaching a conductor to an electrical apparatus.

Terminal Block

An insulating base equipped with terminals for connecting secondary and control wiring. Used on hardwired equipment, such as a UPS, when input plugs and output receptacles are either impractical or unavailable.

Thermal Break

A material of low thermal conductivity placed in such a way as to reduce the flow of heat between two materials of high thermal conductivity.

Thermal Mass

A material that has the ability to absorb, store, and release heat energy. The more heat energy that is required to change the temperature of high-density materials (concrete, bricks, tiles), the more thermal mass the materials have.


Passive solar hot water systems that rely on the natural convection of liquids to collect energy. Designed with the tank above the collection surface.

Thin Film

A PV manufacturing technique where silicon is vapor deposited, a few molecules thick, onto another material.

Three-Phase Power (3Ø)

Power that is provided by a single source with three outputs with a phase difference of 120 ° between any two of the three voltages and currents.

Tilt Angle

A fixed angle measured from the horizontal to which a solar array is tilted. The tilt angle is chosen to maximize the array output. Depending upon latitude, season, and time of day, the optimum angle will vary.

Tilt-up Tower

A non-climbable wind generator tower that tilts up and down to allow installation and servicing of the turbine on the ground. Normally these employ a gin pole—a horizontal lever arm that helps raise and lower the tower.

Top-of-Pole Mount

A PV mount that is installed on the top or side of a pole usually set in concrete. Can be fixed or seasonally tilted.


A mounting rack for a PV array that automatically tilts to follow the daily path of the sun through the sky. A “tracking array” will produce more energy through the course of the day than a “fixed array” (non-tracking), particularly during the long days of summer. Some trackers are single-axis while others are dual-axis.

Transfer Switch

A switch which will transfer current from one circuit path to another without interrupting the flow of the current.


An electrical device that steps up voltage and steps down current proportionally (or vice-versa). Transformers work with AC only.

Transformer (T)

A device that raises or lowers the voltage of an alternating current electrical source.


The fast radical change in a smooth sine wave that occurs in both voltage and current waveforms during the transition from one steady-state operating condition to another.

Trash Rack

A large strainer at the input to a hydro system. Used to remove debris from the water before it enters the pipe.

Trickle Charge

With the trickle charging process, the battery receives a constant voltage feeding a low current. Constant use of this method dries the electrolyte and corrodes the plate, reducing potential battery service life by up to 50 percent.


An engine that produces rotary motion through reaction or impulse, or both, with moving fluid or gas. The resultant rotary motion is usually used to drive an alternator generator.


In hydroelectric systems, a type of impact hydro runner optimized for lower heads and higher volumes than a Pelton runner.

Two-Phase Power

Power which is provided by a single source with two outputs which may be 180 degrees out of phase or 120 degrees out of phase.