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PAGE 22 — DCA-70SSJU SERIES — OPERATION AND PARTS MANUAL (STD) — REV. #5 (06/03/03)
DCA-70SSJU SERIES — GENERAL INFORMATION
DCA-70SSJU Series Familiarization
Generator
The MQ Power Model DCA-70SSJU Series is a 26 kW
generator
(Figure 4) that is designed as a high quality
portable (requires a trailer for transport) power source for
telecom sites, lighting facilities, power tools, submersible
pumps and other industrial and construction machinery.
Engine Operating Panel
The “Engine Operating Panel” is provided with the following:
Tachometer
Water Temperature Gauge
Oil Pressure Gauge
Charging Ammeter Gauge
Engine Throttle Handle (Up to S/N 7302410)
Fuel Level Gauge
Engine Speed Switch (S/N 7302141~)
Cold Starting Button
Panel Light
Panel Light Switch
Ignition/Preheat Switch ( Up to S/N 7302410)
Auto ON/OFF Engine Controller (S/N 7302141~)
Generator Control Panel
The “Generator Control Panel” is provided with the following:
Output Voltage Adjustment Knob
Frequency Meter (Hz)
AC Ammeter (Amps)
AC Voltmeter (Volts)
Ammeter Change-Over Switch
Voltmeter Change-Over Switch
Voltage Regulator
Over-Current Relay
Output Terminal Panel
The “Output Terminal Panel” is provided with the following:
Three 250 VAC output receptacles (CS-6369), 50 amps
Three auxilliary circuit breakers, 250V @50 amps
Two 125 VAC output receptacles, (GFCI), 20 amps
Two GFCI circuit breakers, 120V@ 20amps
Five output terminal lugs (3Ø power)
Control Box
The “Control Box” is provided with the following:
3-Pole, 250 VAC, 175 amp Main Circuit Breaker
Automatic Voltage Regulator
Current Transformer
Emergency Relay
Open Delta Excitation System
The DCA-70SSJU Series generator is equipped with the state
of the art "
Open-Delta
" excitation system. The open delta
system consist of an electrically independent winding wound
among stationary windings of the AC output section.
There are four connections of the open delta A, B, C and D.
During steady state loads, the power from the voltage regulator
is supplied from the parallel connections of A to B, A to D, and
C to D. These three phases of the voltage input to the voltage
regulator are then rectified and are the excitation current for the
exciter section.
When a heavy load, such as a motor starting or a short circuit
occurs, the automatic voltage regulator (AVR) switches the
configuration of the open delta to the series connection of B to
C. This has the effect of adding the voltages of each phase ot
provide higher excitation to the exciter section and thus better
voltage response during the application of heavy loads.
The connections of the AVR to the AC output windings are for
sensing only. No power is required from these windings.
The open-delta design provides virtually unlimited excitation
current, offering maximum motor starting capabilities. The
excitation does not have a "
fixed ceiling
" and responds
according the demands of the required load.
Engine
The DCA-70SSJU and DCA-70SSJU2 are powered by a 4
cycle, water cooled, turbocharged JOHN DEERE
Model
4045TF150 Diesel
Engine. This engine is designed to meet
every performance requirement for the generator. Reference Table
1 for engine specifications.
In keeping with MQ Power's policy of constantly improving its
products, the specifications quoted herein are subject to change
without prior notice.
Mechanical Governor System
The mechanical governor system control the RPM of the
engine. When the engine demands increase or decrease, the
mechanical governor system regulates the frequency varia-
tion to ±.5%. The electronic governor option increases
frequency variation to ±0.25%.
Extension Cables
When electric power is to be provided to various tools or loads
at some distance from the generator, extension cords are
normally used. Cables should be sized to allow for distance in
length and amperage so that the voltage drop between the
generator and point of use (load) is held to a minimum. Use the
cable selection chart (Table 5) as a guide for selecting proper
extension cable size.