Electric Motors: Single-Phase and Polyphase
True or False: A DC motor consists of a field circuit and an armature circuit.
What is True?
The current from ___ is used to determine the branch circuit conductor size for a DC motor.
What is T.430.247?
A 2-pole breaker in a 120/208-V, 3-ph, 4-W panel supplies power to a circuit. This circuit is connected to a 2 hp, 208-V, 1Ø motor. A safety switch is to be installed adjacent to the motor. DETD fuses with a maximum permitted rating of ___ A can be installed in the switch.
What is 25?
___ current is the amount of current that flows in the circuit conductors when a motor is first energized and the shaft starts to rotate.
What is starting?
A ___ AWG conductor is the smallest that can carry 116 amps.
What is 1?
___ is the turning force exerted on the armature in a motor.
What is Torque?
Motor Nameplate Information: 208-230/460-V 3Ø 100 hp
Supply: 3-pole breaker in a 120/240-V, 3-ph, 4-W panel
Minimum size circuit conductors are ___ AWG.
What is 350?
A ___ circuit carries the electric signals directing the performance of the controller but does not carry the main power current.
What is control?
___ is when one leg (phase) of a 3-phase system is lost.
What is single-phasing?
The key to determining the ___ rating of a motor feeder OCPD is to first determine the maximum permitted size or rating of an OCPD of the same type that would be used for the largest motor connected to the feeder.
What is maximum?
A ___ motor can operate on either AC or DC power.
What is universal?
The nameplate for a 15 HP, three-phase motor shows an FLA of 35 amps at 230 volts. What minimum size SOO cord is required to connect the motor to the branch circuit?
What is 4?
The OCPD for a motor branch circuit provides conductor protection against ___.
What is short circuit and ground fault currents?
A(n) ___ is a small pump connected to a system and is intended to maintain pressure in the piping system to an artificially high level.
What is jockey pump?
Fuses are installed in the ___ and used to protect the tap conductors against overload and the motor against short circuits and ground faults.
What is safety switches?
A motor in a(n) ___ enclosure can be used outdoors.
What is TENV?
The current from ___ is used to determine the branch circuit conductor size for a 1Ø motor.
What is 430.248?
The SC & GF protective device opens very quickly in response to high ___ caused by fault currents (SC or GF).
Energized parts within control cabinets and other control enclosures used for fire pump systems shall be ___.
What is located at least 12" above the floor level?
The OCPDs at the termination of the motor feeder tap conductors are required to be sized to ___.
What is protect the motors?
A 1Ø motor is pulling 13 amps when connected to a 240-volt circuit. You know that this type of motor is about 60% efficient and has a power factor of .88. The motor is delivering about ___ hp.
What is 2.2?
Motor Nameplate Information: 115/230-V 1Ø 3 hp
Supply: 1-pole breaker in a 120/240-V, 3-ph, 4-W panel
What minimum size SJ cord is needed to connect this motor?
What is 7?
Despite being banned in residential uses, ___ inhibits rust and corrosion of iron and steel so it may still be used on bridges, railway equipment, ships, lighthouses, and other structures.
A fire pump is permitted to be supplied by ___ the main distribution (service) panel.
What is a fused safety switch connected ahead of?
A three-phase, 240-volt feeder is going to supply power to one 5 hp 3Ø motor, three 2 hp 3Ø motors, and two 1 hp 3Ø motors. The minimum size aluminum THWN/THHN conductors permitted for this feeder are ___ AWG.
What is 6?