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PAGE 16 — DCA125SSIU 60 HZ GENERATOR • OPERATION AND PARTS MANUAL — REV. #3 (01/13/11) 
GENERATOR
The MQ Power Model DCA125SSIU generator (Figure 3) is 
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
 
 Fuel Level Gauge
 
 Engine Speed Switch
 
 Auto START/STOP Engine Controller (ECU)
 
 Panel Light/Panel Light Switch
 
 Pre-Heat Lamp
 
 Warning Lamp
GENERATOR CONTROL PANEL
The “Generator Control Panel” is provided with the following:
 
 Frequency Meter (Hz)
 
 AC Ammeter (Amps)
 
 AC Voltmeter (Volts)
 
 Ammeter Change-Over Switch
 
 Voltmeter Change-Over Switch
 
 Voltage Regulator
 
 3-Pole, 300 amp Main Circuit Breaker
 
 “Control Box” (located behind the Gen. Control Panel)
• Automatic Voltage Regulator
• Current Transformer
• Over-Current Relay
• Starter Relay
• Engine Controller (Computer Controlled)
• Voltage Selector Switch
OUTPUT TERMINAL PANEL
The “Output Terminal Panel” is provided with the following:
 
 Three 120/240V output receptacles (CS-6369), 50A
 
 Three auxiliary circuit breakers, 50A
 
 Two 120V output receptacles (GFCI), 20A
 
 Two GFCI circuit breakers, 20A
 
 Five output terminal lugs (3Ø power)
 
 Battery Charger (Optional)
 
 Water Heater (Optional)
OPEN DELTA EXCITATION SYSTEM
The DCA125SSIU 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 rectifi ed 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 confi guration of the open delta to the series 
connection of B to C. This has the effect of adding the 
voltages of each phase to 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 “fi xed ceiling” and responds 
according the demands of the required load.
ENGINE
The  DCA125SSIU is powered by a 4 cylinder, water cooled,  
direct injection, turbocharged air-to-air intercooled ISUZU 
4HK1X diesel engine. This engine is designed to meet every 
performance requirement for the generator. Reference 
Table 2 for engine specifi cations. 
In keeping with MQ Power’s policy of constantly improving 
its products, the specifi cations quoted herein are subject 
to change without prior notice.
ELECTRIC GOVERNOR SYSTEM
The electric governor system controls the RPMs of the engine.  
When the engine demand increases or decreases, the 
governor system regulates the frequency variation to ±.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 6) as a 
guide for selecting proper extension cable size.
GENERAL INFORMATION