Starting torque shall be sufficient to start the pump to which the motor
will be connected under the maximum conditions specified, but in no case
shall the starting torque be less than 60 percent of full-load torque.
Breakdown torque shall be not less than [200] [150] percent of full-load
torque.
2.1.2.2
Locked-Rotor Current
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NOTE: The locked-rotor current will increase with a
power factor or lower than rated load. This
information shall be taken into account when the
designer is specifying the motor. When inrush
current is particularly critical, due to system
limitations on voltage dip or current, the designer
shall obtain limits from the local utility and
supply this information in this paragraph. The
requirements for locked-rotor current (inrush) shall
be coordinated with power factor and efficiency
requirements of for power factor efficiency
specified below.
**************************************************************************
The locked-rotor current shall not exceed [600] [500] percent of normal
full-load running current. [The locked-rotor current shall not exceed
[_____] amps at 90 percent of rated voltage during any point in the
starting cycle under worst case starting conditions. For reduced voltage
starting, the above criteria shall apply to supply side of the starter.]
2.1.2.3
Starting Capabilities
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NOTE: Frequency of starting must always be
considered in motor applications. The starting
capabilities to be met by all motors are set forth
below. However, the actual motor duty cycle should
be specified in paragraph DUTY CYCLE, along with the
requirement for the special motor starting
nameplate. Undoubtedly, these starting capabilities
will be adequate in most cases since the actual load
inertia, WK2 of the pumps is much less than the NEMA
starting (number of starts per unit of time) is low.
When the frequency of starting is several times per
hour, or the load torque is high, a thorough study
and perhaps a modified motor may be required. To
ensure that all requirements of the specifications
are met, submittal of the operating data should be
required. It is possible that with higher starting
frequencies the rotor may have to operate at
temperatures higher than typical, so that
modifications would be required.
**************************************************************************
Large motors, on the basis of the load torque characteristics and the load
inertia Wk2 listed in NEMA MG 1, paragraphs 20.41 and 20.42, shall as a
minimum be capable of making the starts required in NEMA MG 1, paragraph
20.43. Smaller motors shall conform to the requirements in NEMA MG 1,
paragraph 12.50.
SECTION 16221A
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