Understanding Motor Controls
3rd Edition
ISBN: 9781305498129
Author: Stephen L. Herman
Publisher: Cengage Learning
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Chapter 9, Problem 1RQ
To determine
Identify how the direction of rotation of a three-phase motor can be changed.
Expert Solution & Answer
Explanation of Solution
By changing any of the two motor leads, the direction of rotation of any three-phase motor can be reversed. Separate contactor will be required in each direction since the motor is connected to the power line regardless of the operating direction.
As per NEMA standards, the leads 1 and 3 will be changed for reversing and only one overload relay is needed to protect the motor. A reversing controller is one in which two separate contactors and one overload relay are built as one unit.
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14.25.2.5 kg/s of a solution at 288 K
containing 10 per cent of dissolved solids
is fed to a forward-feed double-effect
evaporator, operating at 14 kN/m² in the
last effect. If the product is to consist of
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PROBLEMS
1179
should be the pressure of the steam? The
surface in each effect is 50 m² and the
coefficients for heat transfer in the first
and second effects are 2.8 and 1.7 kW/
m² K, respectively. It may be assumed
that the concentrated solution exhibits a
boiling-point rise of 5 deg K, that the latent
heat has a constant value of 2260 kJ/kg
and that the specific heat capacity of the
liquid stream is constant at 3.75 kJ/kg K
O
: +0
العنوان
use only
5) A 100 kg batch of granular solids
containing 30% moisture is to be dried in
a tray drier to
15.5% by passing a current of air at 350
K tangentially across its surface at a
velocity of 1.8
m/s. If the constant rate of drying under
these conditions is 0.7 g/s m2
and the critical moisture
content is 15%, calculate the
approximate drying time. Assume the
drying surface to be 0.03
m2
/kg dry mass.
мони
give me solution math not explin
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