UFC 3 -520-01
June 10, 2002
Table 7-2. Motor Altitude Derating Factors
Altitude Range
Altitude Range
Derating by Service Factor
(feet)
(meters)
1.0
1.15
1.25
1.35
3,300 9,000
1,006 2,743
93%
100%
100%
100%
9,000 9,900
2,743 3,018
91%
98%
100%
100%
9,900 13,200
3,018 4,023
86%
92%
98%
100%
13,200 16,500
4,023 5,029
79%
85%
91%
94%
Over 16,500
Over 5,029
Consult Manufacturer
7-1.6. Consult the manufacturer if the motor operating conditions will be unusual. This
includes:
Dirty areas.
Explosive areas.
Areas with chemical fumes.
Salt-laden or oil-laden air.
Excessive voltage and frequency variations from rated values.
7-2
MOTOR CONTROL CIRCUITS.
7-2.1
Provide motor controllers (starters) for motors larger than 0.125 horsepower
(93.25 watts) and apply the design criteria of NEMA ICS 1, Industrial Control and
Systems: General Requirements and NEMA ICS 2, Industrial Control and Systems:
Controllers, Contactors and Overload Relays, Rated Not More Than 2000 Volts AC or
NEC requirements.
7-2.2
The motor starting circuit should be full voltage-type starting (also referred to
as line starting). Energizing the motor with full line voltage is the most economical
starting method and allows the most rapid acceleration. Accordingly, motor controllers
should normally be of the magnetic, across -the-line type.
7-2.3
High-efficiency motors (either Design E or energy efficient Design B) often
have very high starting currents that can cause voltage dips below the system voltage
tolerances. If the starting current will result in more than a 20 percent transient voltage
dip or if the analyzed voltage dip is otherwise determined to be unacceptable (refer to
paragraph 2 -6 for information regarding voltage drop during motor starting), apply one
of the following methods for motor starting:
7-3
Previous Page
