FG2 datasheet(7/52 Pages) ETC

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SECTION 9

SECTION 1

Machine Tool indusTrial conTrol

Data subject to change without notice.

maCHIne tool IndustrIal Control transformer seleCtIon

Selecting a Control Transformer

requires that you have first hand

knowledge of the application for the

transformer and that you understand

some basic terms related to the

selection process. By using the

following information, you will be sure

to select the HPS Imperator® Control

Transformer which best meets your

application.

The HPS Imperator Series

machine tool control transformers

are specifically designed for high

inrush applications requiring reliable

output voltage stability. Designed to

meet industrial applications where

electromagnetic devices such as

relays, solenoids, etc. are used, the

HPS Imperator series transformers

maximize inrush capability and

output voltage regulation when

electromagnetic devices are initially

energized.

To select the proper transformer,

three characteristics of the load

circuit must first be determined.

They are total steady-state (sealed)

VA, total inrush VA, and inrush load

power factor.

(a)

the total steady state

“sealed” VA is the amount of VA

that the transformer must supply

to the load circuit for an extended

length of time. Simply add the total

steady-state VA of all devices in your

control circuit. The operating VA data

of these components is available

from the manufacturers.

(B)

t he total inrush Va

is the amount of Va that the

transformer must supply for all

components in the control circuit

which are energized together.

Some consideration to the start-up

sequence may be required. Inrush VA

should be obtained from the device

manufacturer.

difficult to determine without detailed

vector analysis of all the control

circuit components. Such information

is not generally available. Therefore,

HPS is recommending that a 40%

power factor be utilized. Although

some other control transformer

manufacturers still recommend a

power factor of only 20%, HPS,

through recent tests conducted on

many popular brands of control

devices, has determined that the

40% power factor value is more

accurate.

Once the above circuit variables

have been determined, transformer

selection is a six step process.

sIX easY steps

1. Determine what your Primary

(supply) and Secondary (output)

voltage requirements are, as well

as your required frequency (i.e. 60

Hz)

2. Calculate the Total Sealed VA

of your circuit. (See Step A)

3. Calculate the Inrush VA

by adding the inrush VA of all

components being energized

together. remember to add the

sealed VA of all components that do

not have inrush VA, (lamps, timers

etc.) as they present a load to the

transformer during maximum inrush.

If the inrush for the components in

your circuit are not known, assume

a 40% Inrush Power Factor.

4. Calculate the Total Inrush VA

using one of the two methods:

Total Inrush VA =

(Va sealed)2 + (Va inrush)2

Total Inrush VA =

Va sealed + Va Inrush

note: method B will result in a slightly

larger transformer being selected.

5. If the nominal supply voltage

does not fluctuate more than 5%,

then reference the 90% secondary

voltage column in the regulation

Data Table for the correct VA

rating.

If the supply voltage varies upwards

of 10%, the 95% secondary voltage

column should be used to size the

transformer.

Current standards require

electromagnetic devices to operate

reliably at a minimum of 85%

of their rated voltage. However,

contact life may be affected with

continuous start-ups at that voltage

level. Therefore, the minimum 85%

secondary voltage column should

only be used as a reference.

6. Using the regulation data tables

below, select the appropriate VA

rated transformer:

A) With a continuous VA rating that

is equal to or greater than the value

in Step 2.

B) With a maximum inrush VA

equal to or greater than the value

obtained in Step 4.

To determine the correct HPS

Transformer and its Catalog number,

just refer to the tables in this catalog

for the voltage ratings, frequency

and corresponding VA required.

It is recommended that a Control Transformer be

sized at a 40% Power Factor. Some components

in a circuit, such as electromagnetic devices,

typically operate at that level due to their

inherently lower power factor. Selecting a

transformer at 40% Power Factor will more than

adequately size the unit for all the various loads

in the circuit.

Hps Imperator® transformers

reGulatIon data taBle

Continuous Va

Inrush Va @ 40% power factor

transformer

85%

90%

95%

nameplate

secondary secondary secondary

rating

Voltage

100

150

250

350

500

750

1000

1500

330

350

620

895

1596

2464

3939

6422

9842

12797

259

258

467

699

1229

1889

2854

4778

7102

9018

192

170

321

512

880

1345

1819

3228

4530

5489

For VA sealed definition please refer to 1 (A).

For VA inrush definition please refer to 1 (B).

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