Isolation transformer

DOE-SPEC-3021-97

ATTENTION:

The inrush capabilities are dictated by the connected load and the internal bypass short circuit capability

required is dictated by the clearing time of the protective circuits in the internal bypass source.

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Inrush. The transfer switch shall be capable of carrying the

3.3.5.3

maximum expected inrush of [ ] kVA for [ ] milliseconds at

rated voltage and at [ ] lagging power factor. It shall also be

capable of carrying internal bypass source available short circuit

current specified for [ ] milliseconds.

ATTENTION:

The transfer time should ideally be instantaneous. A realistic time for both the load and the UPS switch is less

than 4 ms or 1/4 of a cycle.

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3.3.5.4

Transfer time. The total transfer time, including sense time, from

the sudden loss of inverter output to the transfer to the internal

bypass source shall not be more than [ ] milliseconds.

Output current. The static transfer switch shall be capable of

3.3.5.5

continuously carrying the rated output current of the UPS system

and the inrush current and short-circuited currents listed in

paragraph 3.3.5.3.

3.3.5.6

Operations. The static transfer switch shall be capable of the

following operations:

a. Continuous operation at full load current.

b. Switching from normal inverter operation to internal bypass and

retransfer back following a 10-second delay. The switch shall

handle the inrush currents involved in the transfer (see

paragraph 3.3.5.3).

ATTENTION:

Isolation transformers are used at the input of the UPS module to attenuate the passage of noise or transients.

This section requires that the user enter the specific parameters of the transformers to be used.

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Isolation transformer. The UPS isolation transformer shall have the following

3.3.6

characteristics: [ ] kVA, [1] [3]-phase, [ ]oC temperature rise, [ ] Hz,

dry-type transformer primary rated [ ] V, [wye] [delta], secondary rated [ ] V,

[wye] [delta], class [ ] insulation, with hot-spot temperature not to exceed [ ] oC rise

over [ ]oC ambient. High-voltage winding shall have two [

]% taps above

nominal and four [ ]% taps below nominal. The transformer shall have [ ]%

impedance (minimum) on its own base. Low-voltage neutral shall be [grounded.]

[brought out for external connection.]