Atec DDA-6000 User Manual
DDA-3000 and DDA-6000
Universal Circuit Breaker Test Sets
■
Model DDA-1 Digital Data Acquisition
Instrumentation and Control System
■
High-current output: 60,000 A for Model
DDA-6000; 35,000 A for Model DDA-3000
■
Digital signal processing (DSP) technology
■
Variable pulse time and firing angle
output current control
■
Compliant with NEMA AB-4 test
guidelines
DDA-3000 and DDA-6000
Universal Circuit Breaker Test Sets
DESCRIPTION
Incorporating the latest technological advancements,
Models DDA-3000 and DDA-6000 Series are designed
specifically to test low-voltage power and molded-case
circuit breakers equipped with thermal, magnetic or solidstate trip devices. The units are fully compliant with NEMA
AB-4 test guidelines.
Tests are performed by simulating an overload or fault
condition. Each test set is an integrated test system that
provides a variable, high-current output. The test sets
incorporate all control circuitry and instrumentation
necessary to test direct-acting circuit breakers accurately,
efficiently and safely.
The unique transformer and circuit design results in a very
high-capacity test set in a very compact size. Advanced digital
control and instrumentation provides exact testing capacity.
APPLICATIONS
Universal in application, the test sets will test virtually all
low-voltage, molded-case and metal-clad, direct-acting ac
circuit breakers produced by General Electric,
Westinghouse, Federal Pacific, Square D, Gould, ABB, ITE,
Siemens and other manufacturers.
Model DDA-3000 is rated for testing breakers up to 3000
amperes. Model DDA-6000 is rated for testing breakers up
to 6000 amperes. Rugged and reliable, Megger circuit
breaker test sets will provide years of trouble-free
operation.
The test sets also may be used for other high-current
applications, such as verifying the ratio of current
transformers and performing heat runs or primar y injection
testing of high-voltage breakers and their associated
protective relays.
All Model DDA-3000 and DDA-6000 test sets have identical
features, instrumentation and operational characteristics.
The only changes in the specifications among the units are
their size, weight and maximum output-current capacity.
FEATURES AND BENEFITS
■
Initiating control circuit: Fully digital initiating
control circuit provides both pulsed and maintained
control modes of output duration. The pulsed mode
automatically pulses the output to any programmed
pulse duration. This provides additional testing
capabilities for electromechanical and solid-state trip
devices. A short pulse duration also limits the preheating
of the breaker under test while setting the test current.
In the maintained mode, the output remains energized
until manually turned off or, during timing test, until the
device under test operates, which both stops the timer
and de-energizes the output.
■
Zero dc offset: Use of digitally controlled SCRs
instead of a contactor to initiate the output of the test set
eliminates closing-time error and thereby ensures precise
initiation at the zero crossover point of the output
current waveform every time. Initiation at the zero
crossover point ensures symmetrical output current by
eliminating dc offset in the current waveform. Therefore
accurate, repeatable test results are assured even with
currents of very short duration, as when conducting tests
of instantaneous or short-time delay trip elements.
DDA-3000 and DDA-6000
Universal Circuit Breaker Test Sets
The digital control of the SCRs also allows the unit to
initiate at any point within 90 degrees of the zero
crossover point of the output-current waveform. This
will allow the intentional insertion of a dc offset into the
waveform for a complete investigation of a breaker’s
operation.
■
Compact enclosure: Improvements in transformer
and circuit design have resulted in a very high-capacity
test set in a single, relatively small enclosure. For safety
and mobility, the test set is housed in a single, rugged,
sheet metal enclosure with a low center of gravity, tow
ring, lifting eyes and large, locking swivel casters with
brakes.
To increase maneuverability, all four casters swivel;
however, they also can be locked into a fixed position
easily. The compact size of test sets permits easy
movement through narrow doors. Controls and
instrumentation are positioned so that the operator can
simultaneously observe the circuit breaker under test.
■
Construction: Built for years of trouble-free, reliable
operation, the test sets include rugged instrumentation
and controls designed to withstand the vibration and
shock of frequent transportation. They need never be
removed from the enclosure .
■
Protection: Fuse, circuit breaker and overload
protective devices are incorporated. The output-initiating
SCRs are forced-air cooled, and temperature sensors
provide protection from overheating. Emergency stop
pushbutton is provided to de-energize all input power to
the test set.
■
Ground safety interlock: An interlock circuit
ensures that the test set chassis is connected to system
ground before the output of the test set can be energized.
■
Accessory outlet: A ground-fault-protected, 120 volt
outlet with a capacity of 1.2 kVA is provided for
convenient connection of accessory equipment. Other
voltages are available internally for customer-installed
outlets.
INSTRUMENTATION AND CONTROLS
Model DDA-1: The Digital Data Acquisition
instrumentation and control system was designed
and accurate metering of the breaker under test.
Model DDA-1 uses the latest in digital signal processing
(DSP) technology. This technology provides complete digital
control of the SCRs and digitally samples the output current
for high-accuracy measurements.
Digital ammeter: Model DDA-1 samples the output
current digitally and mathematically calculates the current
that is supplied to the breaker under test. This process
increases the accuracy of the ammeter systems and
provides extreme flexibility in what current value is
displayed. For example, when the test set is delivering a
continuous current, the digital ammeter is continuously
sampling the output waveform and can display a true rms
value of the current.
For measuring short-duration currents, Model DDA-1 can
calculate the output current in the following ways via
selection from the soft control buttons on the panel:
1. For any output current greater than half a cycle, Model
DDA-1 can calculate the true rms value of the output
current pulse. For any output less than half a cycle, a true
rms measurement is invalid.
2. For any current pulse, Model DDA-1 can measure the
peak current and calculate an anticipated rms value of the
current from the peak current.
This multiple-current calculation feature is also useful
when testing different styles of solid-state trip devices. This
feature allows the test set to simulate a similar type of
current calculation that is being used by the various solidstate trip devices.
Digital timer: Thanks to digital signal processing
technology, Model DDA-1’s system knows exactly when
current is present and when the breaker under test opens.
This provides high-accuracy timing even when testing the
instantaneous trip function on fast-acting breakers. In
addition, the digital timer can display the breaker trip time
in cycles or seconds.
A completely digital, solid-state circuit starts the timer
automatically when the output current starts to flow and
stops it when the device under test operates. This circuit
will accommodate a variety of test conditions including:
The Model DDA-1 control panel digitally samples the output current and mathematically calculates the current supplied to the breaker under test.
Loading...