ETL 1110-2-560
30 Jun 01
M
R
S
T
U
M
M - Circuit Breaker
U - Motor Fast Speed Windings
R - Fast Speed Forward Starter
S - Fast Speed Reverse Starter
T - Fast Speed Conductors to Motor
Figure E-7. Dam gate (DE) electrical mission reliability block diagram
E-3. Reliability Calculation
a. Environmental conditions. The environmental conditions were considered for the ambient
service of the electrical equipment. Determination of the environmental K factor was the same as for the
mechanical equipment (See paragraph D-3b and c). The electrical equipment on the lock and dam was
considered to be exposed to an outdoor marine environment resulting in a K1 factor of 2.
b. Failure rate. The failure rates of all applicable components were obtained from the published
literature of American National Standards Institute/Institute of Electrical and Electronics Engineers
(ANSI/IEEE) (1980) and Reliability Analysis Center (1995). Typical component failure rates from these
two sources are provided in Tables E-1 and E-2, respectively. The typical failure rates were adjusted in
the analysis to the environmental conditions of the lock.
λ′ = λK
(E-7)
where
λ′ = adjusted failure rate
λ = typical failure rate
K = environmental factor = 2
c. Duty cycle.
(1) Failures of electrical equipment often correspond to voltage and/or current parameters. Failure
rates are typically provided in "operating hours" or "experience hours," which by definition are a duration
of exposure to voltage and/or current. Since voltage and current applied to equipment are near zero when
they are not in operation, the total mission time was adjusted with a duty cycle factor. The duty cycle
factor is the ratio of actual time the equipment is energized by voltage and/or current to the total mission
time t:
t′ = td
(E-8)
where
E-4
Previous Page
