Final motor industrial wiring
A 25-horsepower, three-phase induction motor has a nameplate rating of 32 amperes. The nameplate also shows a temperature rise of 30 degrees C. What is the overload size for this motor in amperes?
40amps
Which NEC table lists the running currents for single-phase AC motors?
430.248
A one-horsepower motor will have a full-load current of ____ amperes when connected to 90 volts DC.
12.2
Conductors in capacitor circuits must be rated no less than ____ percent of the current rating of the capacitor.
135%
Transformers are typically designed for ____-hertz operation.
60 Hz
In a pure inductive load the current will lag the voltage by ____ degrees.
90 degrees
The voltages of a two-phase system are ____ degrees out of phase with each other.
90 degrees
An electronic device that is often used to help overcome the problem of induced noise is the ____.
Differential amplifier
The phasor rotation of a negative harmonic causes an induction motor to produce ____.
Less torque
A capacitor does not require a separate disconnect means if it is connected to the ____ side of the motor overload protective device.
Load
The ____ is used to program the CPU.
Loading terminals
A dielectric test set often used for testing capacitors is generally referred to as a ____ because of its ability to produce a high voltage or high potential.
HIPOT
When two parallel feeders are installed to each of the synchronous condensers, the conductors can be sized for ____ the value of the required ampacity.
Half
The most accurate method for determining whether there is a harmonics problem is to use a(n) ____.
Harmonic analyzer
Harmonic currents in the neutral conductor induce ____ currents into the communication cable.
High-frequency
The approximate starting current of a squirrel-cage motor can be determined by multiplying the kVA rating listed in Table 430.7(B) by the ____ rating and then dividing by the applied voltage.
Horsepower
When current begins to flow through a(n) ____, a magnetic field expands around the ____.
Inductor
In the relay method of isolation, the CPU is isolated through the use of a(n) ____.
Magnetic field
Harmonics are produced by loads that draw current in ____.
Pulse
A pure ____ element causes the voltage and current to be in-phase with each other.
Resistive
When a two-phase, three-wire system is used, the size of the neutral conductor must be increased by ____.
The square root of 2
____ motors are often made to have a leading power factor by overexcitation of the rotor current.
Synchronous
The ____ is a rotating electrical machine that has no electrical or mechanical loads connected to it.
Synchronous condenser
The current rating of most outputs can range from 0.5 to about ____ amperes, depending on the make of the controller and the type of output being used.
Three
It is necessary to use an ammeter that responds to ____ current when making a check for harmonics.
True RMS
A(n) ____ is connected across the AC input to help eliminate any voltage spikes that may occur.
metal-oxide varistor
The PLC recognizes only ____.
open or close contacts
Two-phase motors that are especially designed for ____ applications use the same rules for determining full-load currents as single-phase motors.
Low speed-high torque
Apparent power is generally called ____.
Volts-amps
The amount of capacitance needed can be determined by connecting a(n) ____, ammeter, and voltmeter to the circuit.
Wattmeter
A 100-horsepower, three-phase squirrel-cage induction motor is connected to a 240-volt line. A dual-element time-delay fuse is to be used as the short-circuit protective device. What is the correct fuse rating?
450
Harmonics are voltages or currents that operate at a frequency that is ____ the fundamental power frequency.
A multiple of
PLCs are designed to be programmed with ____.
Ladder diagrams
Harmonics called ____ have a zero sequence.
Triplens
When the power factor of the plant is 1.0 (unity), the kilovarmeter reads ____.
0
A ratio of ____ between measurements made with a true RMS ammeter and an average value ammeter indicates no harmonic distortion.
1.0
Ammeters that respond to the average value convert the alternating current into direct current. This value must be increased by a factor of ____ to change the average reading into the rms value for a sine wave current.
1.111
The instantaneous peak value of current is equal to the rms value multiplied by ____.
1.414
Assume that an inductor has an inductive reactance of 100 ohms and the wire has a resistance of 10 ohms. What is the impedance?
100.5
In a three-phase circuit, the apparent power can be computed using this formula: VA = volts times ____ times the square root of three.
Amps
PLCs were first used by the ____ industry in the late 1960s.
Automotive
Most common squirrel-cage motors used in industry fall into the design ____ classification.
B
The ____ is the "brains" of the PLC.
CPU
Highlighting a contact means that there is a ____ through that contact.
Complete circuit
The PLC is a special type of ____ designed to perform a special function.
Computer
A ____ is used to smooth the pulsations caused by a bridge rectifier.
Filter capacitor
The temperature ratings of devices such as circuit breakers, fuses, and terminals are found ____.
In UL product directories
If a synchronous-type motor is operated at 90 percent power factor, the rated full-load current in the table is to be ____.
Increased by 10%
The actual logic of the control circuit is performed by ____.
Internal relays
To minimize interference, communication cables are run as close to the ____ conductor as possible.
Neutral
Most capacitors used in industry, especially for power factor correction, are called ____ capacitors.
Non-polarized
The motor overload size is to be determined by using the current listed ____.
On motor nameplate
Electrical noise is such a problem in some installations that several manufacturers are using ____ instead of wires for connection to the I/O rack.
Optical cables
The most popular way to isolate the CPU from the external circuit is through ____.
Optical isolation
The ____ is used to connect the CPU to the load.
Output module
When testing capacitors, if the capacitor is good, the microammeter should indicate ____ current.
Zero
Most motor circuits are protected by dual-element time-delay fuses or ____.
inverse-time circuit breakers
One way to deal with harmonic problems is to install a ____ neutral conductor.
larger
THDF stands for ____.
transformer harmonic derating factor
