Electrical Engineering Terms R


A contraction of the term reinforcement bars, which are half-inch wrought-iron rods suspended in poured concrete to give it added strength.

Rated Load.

The torque value of the connected load that occurs when the horsepower requirements of the driven load equate to the horsepower rating of the motor and the electric motor is supplied its rated voltage at rated frequency (AC motors) as listed on the nameplate.

Rated-Load Current (RLC).

Normally abbreviated to the acronym RLC, this is a qualifying term found on the nameplate of hermetic refrigerant electric motor-compressors. This value of current occurs when the motor-compressor is operated at the rated load, rated voltage, and rated frequency as listed on the nameplate.

Revolutions per Minute or RPMs.

Also referred to as baseline or full-load speed: the speed at which an electric motor will operate at rated load. See Baseline Speed.

Running Overload.

An operating condition in which the torque requirements of the driven load exceeds the horsepower rating of an electric motor. Because the rotor turns at less than the baseline speed specified on the motor nameplate, the electric motor draws current in excess of its full- or rated-load current as specified on the motor nameplate.


A variable or adjustable resistor constructed with part of its resistive path exposed such that moving and setting one or more movable contacts can change its resistance. As compared to a potentiometer, which is also a variable or adjustable resistor that is used to pick off a voltage in an electrical circuit (voltage divider), a rheostat is a variable resistor that can be adjusted to increase or decrease the circuit current, without opening the electrical circuit in which it is connected. Because it can be varied while energized, a rheostat is normally used only in a power circuit.

RMS Value

Root mean square value or effective value, it is equal to 0.707 times the peak value.

RC Time Constant

The fixed time interval which is equal to the resistance times the capacitance in a series RC circuit.

Reactive Power

The rate that energy is either stored or returned from a capacitor.

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