ELTK1200 Formula Sheet

Induced Power Factor

Capacitance

Frequency

Resistors in series

Angular velocity in parallel

Peak, Peak to Peak, RMS

Capacitors in series

Capacitors in parallel

Inductors in series

Real in parallel

Q-Factor

1 Pure

Instantaneous equations

RMS

Instantaneous waveforms Diagram

Phase Relationship:

I and VS are “in phase”.

2 Pure inductor

Instantaneous equations

I as reference.

RMS

VS as reference (See Note).

Instantaneous waveforms Phasor Diagram

Phase Relationship: I as reference (starts at 0). I lags VS by 90°.

Note: The instantaneous equations depend upon which waveform is taken as a reference.

Phasor diagrams use current I as a reference, but sometimes problems give VS as reference ( ) and you must calculate I.

For the rest of this formula sheet, current I will be the reference.

3 Series RL circuit

Instantaneous equations

Instantaneous waveforms

RMS

Impedance Triangle Phasor Diagram Power Triangle

Phase Relationship: I lags VS by 2 (angle between 0° and 90°).

4 Pure

Instantaneous equations RMS

Phasor Diagram

Instantaneous waveforms

Phase Relationship:

I leads VS by 90°.

5 Series RC circuit

Instantaneous equations

Instantaneous waveforms RMS

Impedance Triangle Phasor Diagram Power Triangle

Phase Relationship: I leads VS by 2 (angle between 0° and 90°).

6 Series RLC circuit

Instantaneous equations and waveforms depend on whether the angle is lagging (See Series RL circuit) or leading (See Series RC circuit).

NOTE: If XL > XC (VL > VC, QL > QC), circuit is RMS inductive, ˆ lagging phase angle. If XL < XC (VL < VC, QL < QC), circuit is capacitive, ˆ leading phase angle. If XL = XC (VL = VC, QL = QC), circuit is resistive, ˆ in phase, resonant frequency.

Impedance Triangle Phasor Diagram Power Triangle

Phase Relationship: I leads/lags VS by 2 (between 0° and 90°). Lagging phase angle shown. See NOTE.

7 Resonant frequency Three phase

Wye (Y)

Delta ())

Power

General Transformer equation

Relationship between I and VS for all Series Circuits.

L I lags VS by 90°. Inductive 2 RL I lags VS by 2. Transformation ratio Resistive R I and VS are in phase. RC I leads V by 2. 2 Capacitive S C I leads VS by 90°. 1 1 RLC I leads/lags VS by 2. Transformer capacity 1 Depends on values of L, C and f. 2 between 0° and 90°.

ELI the ICEman drinks RIE. ELI drinks RIE and ICE.

ELI = I lags VS by 90° for L circuits. RIE = I and VS are in phase for R circuits. ICE = I leads VS by 90° for C circuits. Transformer losses and efficiency

8 rev 5