Reliability Prediction Analyses

What is Reliability Prediction Analyses (RPA)?

RPA is the quantitative evaluation of a product’s Reliability performance. It entails Failure Rate (ʎ) and Mean Time Between Failure (MTBF) estimations.

Definitions:

  • MTBF is calculated as the arithmetic mean (average) time between failures of a
    system.
  • MTBF unit is depicted in hours.

In general, MTBF is the "up-time" between two failure states of a repairable system during operation as outlined here:

Failure timeline diagram

Equations:

RPA-Equations

Reliability Graph (Bathtub Curve):

Bathub Curve

Notes:

  1.  Constant failure rate (ʎ) is utilized to estimate MTBF.
  2. Environmental Stress Screening (ESS) addresses infant mortality failures during manufacturing process. ESS eliminates manufacturing defects.
  3. Weibull Analyses predicts Wear Out failures.

Weibull Analyses:

A statistical analysis that predicts the probabilities of infant mortality and wear out
failures.

Dansob Weibull Analyses emphasizes on wear out failures only.

Objective:

The primary objective of Weibull Analyses is to espouse and improve product reliability by introducing Scheduled Maintenance Interval (SMI).

SMI is established by converting an exponential probability density function into a constant probability density function.

Equations:

Weibull Statistical Analysis

F(t, ʎ, k) = Probability Density Function
k = Shape Parameter
ʎ = Failure Rate (per hour)
t = time (in hours)

Graph:

Weibull Analysis Graph

Electric Machine Solutions

- AC Machines -

squirrel cage induction motor

Wound Rotor

motor showing rotor and stator windings

Squirrel-Cage Rotor

Induction Motors

Electric Machine Solutions

Cylindrical-Pole Rotor

Mechanical motor components

Salient-Pole Rotor

Synchronous Motors

- DC Machines -

Precision servo motor

Brushless DC Motors

Electric motor
Silver metal DC gear motor

Permanent Magnet DC Motors

- Winding Configurations -

Outer rotating ring
inner rotor motor
brushless DC motor
rotating electric motor

- Finite Element Analyses -

spiral motor winding
Spiral coil winding pattern
Motor cross-section
Engineering analysis of motor design