# Staco Energy Products Company - How to Order and Specify Variable Transformers Selecting the Staco Variable Transformer best suited for your specific requirements is easy once you make the following basic determinations:

### Input:

1. Line Voltage
2. Single or Three Phase
3. Frequency

### Output:

1. Voltage
2. Amperage
3. kVA

To assist you in making the proper selection, an explanation of Staco's standard numbering system is described below.

## The Staco Product Numbering System

The basic single units (open construction) are identified by 3 or 4 digits, i.e., 501-C, 1010B, 5021, etc.

• The first two digits designate the current
• the third, voltage
• the fourth is simply a decimal locator.

1.  In a 3 digit number, the first digit indicates amperes, the second indicates the additional fraction of amperes, the third indicates voltage.  For example, with the 501-C the 50 indicates 5.0 amperes and the 1 indicates a 120 volt line.

2.  In a 4 digit number where the third digit is one, the first two digits indicate amperes, the third designates 120 volts.  For example, with the 1510, the 15 indicates 15.0 amperes, the 1 indicates 120 volts, and the 0 is a decimal locator.

3.  In a 4 digit number where the third digit is 2, the first two digits are twice (approximately) the amperes, and the third indicates 240 volts.  For example, with the 6020, the 60 indicates that the amperage is approximately 2X the current rating (about 35 amperes), the 2 indicates 240 volts, and the 0 is a decimal locator.

## Prefixes and Suffixes

Staco Variable Transformers are available in many different configurations.  These other models can be identified by adding the following prefixes or suffixes to the basic 3 or 4 digit numbers.

### Prefixes:

"5"  etc. = speed in seconds of travel,

"M" = motorized

"3PN" = 3 prong cord and receptacle

"J" = Isolated unit

"L" = L series (fully enclosed)

### Suffixes:

"2" through "27" = ganged units (2=2 ganged, etc.)

"A" = Ammeter

"C" = Cased

"D" = Delta connected

"E" = NEMA 1 drip-proof enclosure

"G" = Military

"H" = 400 Hertz

"K" = Less knob

"N" = Less dial

"P" = Parallel connected

"PS" = Parallel series, connected

"S" = Series connected

"T" = Terminal box

"V" = Voltmeter

"W" = Wattmeter

"Y" = Wye connected

*NOTE:  When part numbers end in B or -B, the B is not considered or used as a suffix.

## 120 Volt Series Unit Ratings

 Series Max. Constant Current Amperes* Constant Impedance 171 1.75 2.2 201 2.0 2.5 221-B 2.5 3.2 291 3.0 3.5 501-B 5.0 7.0 1010B 10.0 13.0 1210B 12.0 15.0 1510 15.0 20.0 2510 25.0 30.0 5011 50.0 -- 6011 60.0 --

## 240 Volt Series Unit Ratings

 Series Max. Constant Current Amperes* Constant Impedance 252 0.8 1.0 1020B 3.5 5.0 1220B 5.0 7.0 1520 9.5 12.0 2520 10.0 13.0 5021 28.0 -- 6020 35.0 --

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