ETI AD-1, AD-2 Instruction Manual

INSTRUCTION MANUAL

Portable AC DC Power Supply

Model AD-1

Electrical Test Instruments, Inc.

1301 Avondale Road, Suite J

New Windsor, MD 21776

www.etiinc.com

[phone]

Fax [phone]

Electrical Test Instruments, Inc.

Product Description and Specifications

1 kVA ACDC Power Supply Model AD-1

Overview:

This is a small portable AC and DC power supply intended for circuit breaker charging
motors and other general purpose applications. It will provide DC voltage in three
nominal ranges from 0 to 120, 240, and 480 volts at 1 kVA, and AC voltage in three
nominal ranges from 0 to 140, 280, and 560 volts at 1.4 kVA. It is housed in a rugged
aluminum enclosure approximately 13” x 9” x 12”, and weighs less than 50 lb.

Basic Description and Operation:

This instrument is housed in a rugged waterproof case with a hinged lid. The input
connection is by way of a recessed three prong male inlet compatible with standard
extension cords. The input is protected and controlled by a 10 amp single pole circuit
breaker. When it is turned ON, a single or dual deck variable autotransformer (vernier)
is energized, and a green POWER ON light is illuminated, as well as a 0-600 volt digital
meter. The output arm(s) are protected by a two pole breaker. The variable output of the
vernier is connected to the primaries of two 700 VA toroidal transformers. The
secondaries are connected in series and parallel configuration by means of a multi-deck
six position selector switch. The AC output is monitored by the 0-600 VAC digital meter.
An additional resistor is added in DC mode to read the DC output voltage for open
circuit or resistive loads.

The output is controlled by means of a three position illuminated rotary switch. It has a
maintained and momentary position, and a center OFF. When turned ON, a relay is
energized and the internal lamp is illuminated. The contacts of the relay provide AC
voltage directly to one pair of yellow binding posts, and through a full wave bridge
rectifier to a pair of red and black binding posts. LED indicators next to the binding posts
and near the meter indicate AC or DC mode.

A 20 kOhm load resistance is connected to the DC output along with a 12 volt zener
diode and an indicator LED. This provides a 3-12 watt load for the DC output, and
indicates if there is an output voltage above about 20 volts as a safety precaution.

This power supply has no filter capacitors, and is intended to be operated with no load
capacitance. If a capacitive load is applied, the output voltage may increase t o as much
as 140% of the unfiltered output value, and the voltmeter will not read correctly. The
voltmeter will read the unloaded AC voltage that will be applied to the output. The actual
AC voltage will drop by as much as 11% under rated load, and the voltmeter will read
the actual voltage. The calibration resistor for DC will be set so that the voltmeter reads
the expected DC output at no load, but this will drop by 11% or more depending on
actual load. Snubbers are connected across the output terminals to reduce noise and
high voltage spikes when connected to inductive loads.

The TIMER jacks may be used to start an external timer when the output voltage is
applied to the load. These contacts consist of a solid state relay rated at 0.1 amps and
200 V.