transformers 2

common mode noise

? is a type of electromagnetic interference induced on power or communication lines.

notch

A ? is a distortion in a voltage waveform where the voltage quickly drops toward zero and then returns to the correct value.

choke

A ? is a reactor used to restrict the current to AC or DC drives in the case of short circuits in the drive itself.

common mode choke

A(n) ? is a reactor used to reduce common-mode noise current generated by the rapid switching of a motor drive or a signaling device.

across the entire coil

For a step-down autotransformer application, the source is applied ? , which acts as the primary.

across only part of the coil

For a step-up autotransformer application, the source is applied ? .

pulses

IN VFD's unwanted ________ are caused by fast changing voltages from the drive due to stray capacitance and inductance through the system.

240.21(C)(2)

NEC SECONDARY 10FT RULE

1.2 kva

The load power for a buck-boost transformer that boosts the source by 30 volts at a current of 40 amperes is ? .

125%

Where primary-only protection for transformers is provided with rated currents of nine amperes or more, the basic rule requires that each transformer rated 1,000 volts, nominal, or less be protected by an individual overcurrent protective device on the primary side, rated or set at not more than ? of the rated transformer primary current.

variable frequency drives

__________ are a common source of commonmode noise.

electrostatic shields ungrounded

______________ can prevent common mode noise from transferring from the transformers primary to the secondary only if the secondary is _____________

output reactors

______________ help eliminate vooltage spikes or reflected wave noise by slowing down the rate of change in the drive output voltage

common mode noise

________________is a type of electro magnetic interference induced on power or communication lines

drive isolation transformer nonlinear

a _________________ is deisgned with additonal reactance to reduce power quality problems associated with the effects of ____________loads.

drive switching.

a common mode choke provides high inductance and impedance generated during _____________

split the percentage of change

an auto transformer can be installed in combination with the tap changer to________________________________ as the changer is operated.

any 3 phase

autotransformer reduced voltage starting can be used with __________motor

short circuit

because the impedance of an auto transformer is lower than that of a two winding transformer higher current flows when a __________fault occurs

fluctuating loads 208/120 3p

buck boost transformers should not be used to buck or boost _______________. should aslo not be used to create 240/120 1p service from ________ source

9a. 167% 125%

for auto transformers the NEC has different rules for less than or more than _________. 9a or less OCPD can be rated not more than _____ 9a or more the OCPD can be rated not more than _____

transient and impulse

grounding the secondary provides superior___________and__________ immunity to the load side of the transformer

240.6(A)

nec standard ocpd raTINGS

450.3(b)

nec transformers ocpd table

current flow

reactance is the opposition to ______ in an AC circuit

series

the maximum amount of buck or boost occurs when the secondary is wired in ____________