Reactors and Isolation Transformers
This is a distortion in a voltage waveform where the voltage quickly drops toward zero and then returns to the correct value.
What is a notch?
This is any transformer in which the primary and secondary circuits have a portion of their two windings in common
What is an autotransformer?
This is a small transformer designed to lower or raise line voltage
What is buck-boost?
Table 450.3 (B)
What is maximum rating or setting of OCPD for xfmrs 1000v and less?
Conductors supplied by the secondary side of a single-phase transformer having a 2-wire (single-voltage) secondary, or a three-phase, delta-delta connected transformer having a 3-wire (single-voltage) secondary, shall be permitted to be protected by overcurrent protection provided on the primary (supply) side of the transformer, provided this protection is in accordance with 450.3 and does not exceed the value determined by multiplying the secondary conductor ampacity by the secondary-to-primary transformer voltage ratio.
What is 240.4(F)?
All two-winding transformers are this type of transformer.
What is isolation?
For a step-down autotransformer application, the source is applied across this which acts as the primary
What is the entire coil?
A buck-boost transformer is typically used to change voltage by between these percentages.
What is 5-25%?
T240.6 (A)
What is standard ampere ratings for fuses and inverse time circuit breakers?
The standard ampere ratings for fuses and inverse time circuit breakers shall be considered as shown in Table 240.6(A). Additional standard ampere ratings for fuses shall be 1, 3, 6, 10, and 601. The use of fuses and inverse time circuit breakers with nonstandard ampere ratings shall be permitted.
What is 240.6(A)?
The opposition to current flow that is only present in AC is this.
What is reactance?
For a step-up autotransformer application, the source is applied across this.
What is part of the coil?
When a buck-boost transformer has current less than nine amperes, an overcurrent protection device is allowed to be rated at not more than this percentage of the input current
What is 167%?
240.4 (B)
What is OCPD rated 800A or less?
Maximum Rating or Setting of Overcurrent Protection for Transformers 1000 Volts and Less (as a Percentage of Transformer-Rated Current)
What is T450.3(B)?
This is a type of electromagnetic interference induced on power or communication lines.
What is common mode noise?
This type of transformer is a continuously adjustable autotransformer consisting of a single layer of wire wound on a toroidal core, and a carbon brush that traverses this winding
What is variable?
When a buck-boost transformer has current of nine amperes or more, an overcurrent protection device is allowed to be rated at this percentage of the full-load current
What is 125%?
T310.16
What is ampacities of insulated conductors not more than 3 current carrying conductors in raceway, cable, or earth?
The next higher standard overcurrent device rating (above the ampacity of the conductors being protected) shall be permitted to be used, provided all of the following conditions are met:
What is 240.4(B)?
This is a reactor used to reduce common-mode noise current generated by the rapid switching of a motor drive or a signaling device
What is a common mode choke?
For a load with a very high starting torque, the autotransformer can be tapped to deliver this percentage of the voltage
What is 80%?
When current in a buck-boost transformer is more than nine amperes and the calculated fuse rating does not correspond to a standard fuse rating, this is permitted.
What is the next higher fuse rating?
T310.15(C)(1)
What is adjustment factors for more than 3 current carrying conductors?
A set of conductors feeding a single load, or each set of conductors feeding separate loads, shall be permitted to be connected to a transformer secondary, without overcurrent protection at the secondary, as specified in 240.21(C)(1) through (C)(6). Section 240.4(B) shall not be permitted for transformer secondary conductors.
What is 240.21(C)?
This helps eliminate voltage spikes by slowing down the rate of change in the drive output voltage
What are output reactors?
For voltage regulation, an autotransformer can be installed in combination with this to split the percentage of change
What is tap changer?
This amount of buck or boost occurs when the secondary is wired in series.
What is the maximum?
240.21
What is location in a circuit?
Conductors shall be permitted to be tapped, without overcurrent protection at the tap, to a feeder as specified in 240.21(B)(1) through (B)(5). The tap shall be permitted at any point on the load side of the feeder overcurrent protective device. Section 240.4(B) shall not be permitted for tap conductors.
What is 240.21(B)?
This is designed with additional reactance to reduce power quality problems associated with nonlinear loads
What is a drive isolation transformer?
The lower voltage start draws a smaller line current than this.
What is higher voltage?
For buck-boost transformers, the NEC® makes a distinction between those rated at less than this and those rated at that amount of current or more
What is 9A?
240.21(B)
What is feeder taps?
The secondary conductors shall have an ampacity that is not less than the value of the primary-to-secondary voltage ratio multiplied by one-third of the rating of the overcurrent device protecting the primary of the transformer.
What is 240.21(C)(6)(1)?
This is a coil added in series with a load to reduce inrush current, voltage notching effects, and voltage spikes
What is a reactor?
This during motor starting results in reduced current and torque
What is reduced voltage?
A grounding autotransformer needs to have a rating equal to the maximum possible unbalanced load current on this of a 4-wire system.
What is the neutral?
240.21(C)
What is XFMR secondary conductors?
The total length of one primary plus one secondary conductor, excluding any portion of the primary conductor that is protected at its ampacity, is not over 7.5 m (25 ft).
What is 240.21(B)(3)(3)?