motor calculations
If the total resistance of two motor windings connected in parallel is 24Ω and 240V is applied to the circuit is energized
10A
if the total resistance of two motor windings connected in parallel is 20v and 280v is applied to the circuit how much current will flow?
14A
If 480V three phase motor control center feeds a 50Hp motor (65a) a 40hp motor (52a) and a 10hp motor (14a) the minimum feeder ampacity is
161.25A
Synchronous speed of a 60Hz induction motor with four stator poles
1800 rpm
what is the maximum value for a short circuit protection for multi- motor branch circuits
250% of the smallest motor
The synchronous speed of a 60Hz motor with 2 poles is
3,600 rpm
For ordinary motors, the short-circuit/ground-fault protection for noontime-delayed fuses are sized at what percentage of the motor full current?
300%
the maximum recommended size of a dual element,time delay fuse for a 50hp,460v three phase motor rated at 65 fla is
80a
in addition to short circuit protection, MSCPs also serve as a
Disconnecting means
which of the following describes MSCPs?
Fuse-like devices designed for use only in a special type of fusible-switch combinations motor starter
Installation of capacitors on induction motors will
Improve voltage stability
When used for short circuit protection of motor branch circuits, which of the following must be adjustable and used in conjunction with combination motor starters?
Instantaneous trip circuit breakers
Which of the following list full load currents for three phase motors with a known winding type, horsepower, and voltage
Nec 430.250
the requirements for sizing multi-motor branch circuits can be found in
Nec 430.53
The requirements for torque motors shaded-pole motors and AC adjustable-voltage motors can be found in
Nec 430.6
One of the three factors that will cause a three-phase motors magnetic field to rotate is that the
Stator windings around the inside of the motor are arranged in a specific manner to induce rotation
Which of the following is true concerning the starting current of an induction motor at the moment the circuit is energized?
The current rises rapidly
Good electrical protection for a motor includes both proper overload protection and
current-limiting short-circuit protection
In certain motor circuits, one switch can serve as both the controller and the
disconnecting means
the rotating speed of an induction motor is determined by the number of stator poles and the
frequency of the AC line in hertz
To calculate the maximum safe load that a motor may be expected to carry continuously at its rated voltage and frequency, the service factor is multiplied by the
horsepower rating
which of the following is considered to be one of the Nec requires categories of motor protection
overload protection
If a motor has a current draw of 20A at 240V, what will the amperage be if 480V is applied?
10A
Most effective method of power factor correction in the installation of
Capacitors
All motor circuits contain
over current protection
