What is a Load Bank?
Load Bank? |
Load Banks |
& Malfunction Detection |
LBD Series - Stationary, Resistive Engine Radiator Airflow Cooled
LBS Series - Portable/Stationary, Resistive, Resistive/Reactive, Freestanding Forced Air Cooled
LBW Series - Stationary, Resistive, Freestanding, Water-Cooled
Simplex Load Banks can be used to satisfy the requirements of the National Fire Protection Association (NFPA) for emergency stand-by power systems. These requirements concern acceptance testing and periodic on-site testing and maintenance of emergency and stand-by power systems. The essence of the requirements is that emergency and stand-by power systems are to be tested under load.
Saturn Series Load Bank
NFPA 110 - Emergency and Standby Power Systems, Sections 5-13, 6-3, 6-4
NFPA 99 - Health Care Facilities, Section 3-4.4.1.1 (b)
NFPA 70 - National Electric Code, Section 700-4 (b)
Types of Load Banks
of page |
Resistive Load Bank
A Resistive Load Bank, the most
common type, proves equivalent loading of both generator and
prime mover. That is, for each kilowatt (or horsepower) of load
applied to the generator by the Load Bank, an equal amount of
load is applied to the prime mover by the generator. A resistive
Load Bank, therefore, removes energy from the complete system:
Load Bank from generator—generator from prime mover—prime
mover from fuel. Additional energy is removed as a consequence
of resistive Load Bank operation: waste heat from coolant, exhaust
and generator losses and energy consumed by accessory devices.
A resistive Load Bank impacts upon all aspects of a generating
system.
The “load” of a Resistive Load Bank is created by the
conversion of electrical energy to heat by power resistors. This
heat must be dissipated from the Load Bank, either by air or
by water, by forced means or convection.
In a testing system, a resistive load simulates real-life resistive
loads, such as lighting and heating loads as well as the resistive
or unity power factor component of magnetic (motors, transformers)
loads.
Reactive Load Bank
A “reactive” load includes inductive (lagging power factor) and/or capacitive (leading power factor) loads.
Inductive loads, the more common type, consist of iron-core reactive elements which, when used in conjunction with a resistive Load Bank, create a lagging power factor load. Typically, the inductive load will be rated at a numeric value 75% that of the corresponding resistive load such the when applied together, a resultant 0.8 power factor load is provided. That is to say, for each 100KW of resistive load, 75KVAR of inductive load is provided. Other ratios are possible to obtain other power factor ratings. Inductive loads are used to simulate real-life mixed commercial loads consisting of lighting, heating, motors, transformers, etc. With a resistive/inductive Load Bank, full power system testing is possible given the impact of reactive currents on generator/voltage regulator performance as well as effects on conductors and switchgear.
Variable power
factor loading is possible with a Resistive/Reactive Load Bank
by adjusting the ratio of resistive to inductive load.
A Capacitive Load Bank
is similar to a reactive load bank in rating and purpose, except
leading power factor loads are created. These loads simulate
certain electronic or non-linear loads typical of telecommunications,
computer or UPS industries.
Operating Modes & Malfunction Detection
of page |
Automatic
Generator exercise, control from remote control contacts
Automatic exercise/test via programmable microprocessor
control
Automatic load leveling/load regulation to maintain preset
load on generator by sensing of total load and automatic addition
or subtraction of load bank component
Reverse power/regenerative power protection of generator
by sensing power direction and magnitude and automatic addition
of load bank component to act as a power sink
Manual
Generator exercise and testing
via local or remote manual control
Minimum loading of generators
Malfunction Detection
Simplex Load Banks are equipped
with a malfunction detection system which provides automatic
load disconnect and alarm on sensing of an abnormal operating
condition. The system includes:
Cooling air intake temperature switch, set at 120°F,
to sense recirculation of load bank hot exhaust air or an ambient
temperature above the rating of the load bank
Exhaust Temperature Switch
Cooling air exhaust temperature
switch, set 75°F
above maximum rise at maximum ambient, to sense restricted cooling
airflow, recirculating air, loss of airflow
Air pressure switch to sense for positive cooling airflow
Overvoltage, dual/multi-voltage load banks
Automatic load disconnect/lockout circuit
Remote alarm contacts
Load Elements
of page |
Powr-Web
Resistive Load Element
Simplex Load Banks utilize
the UL Recognized, “Powr-Web” load element. The “Powr-Web”
is an advanced design, air-cooled power resistor specifically
designed for application to load bank systems. The “Powr-Web”
is conservatively operated at half the maximum temperature rating
of the alloy and features a short-circuit-safe design based on
continuous mechanical support of the resistor by high temperature,
ceramic clad stainless steel rods. The “Power Webs”
are assembled into discrete trays which are assembled in a vertical
“stack.” Each tray in the “stack” is independently
serviceable without disturbing adjacent trays.
Specifications
Alloy: FeCrAl
Max. continuous temp. rating: 1920°F
Maximum operating temperature as applied in Load Bank: 1080°
F
Cool down time from operating to ambient temperature: 10 seconds
Simplex Powr-Web
Resistive Load Element Trays
Construction
Calibrated to specific ohm value
Welded lugs on each end
All load elements are continuously supported by vibration resistant,
ceramic clad, stainless steel throughrods
Ratings
3333W at 120V
4170W at 139V
8333 watt 240/480V
16,777 watt at 480V
Water-Cooled Elements
Water-Cooled Load Banks use
specially designed, inconel sheath resistive conductors. The
elements are housed inside a steel load module.
Simplex Inductive
Load Elements
Inductive Load Elements
The Simplex inductive Load Banks utilize discrete iron-core load elements. These elements are non-saturable, air gap calibrated, air cooled devices and field replaceable. Elements may have a temperature sensor embedded in the windings used to detect element overheating and activate the malfunction detection system which disconnects the load elements and activates an alarm. Standard elements are varnish coated; epoxy coatings are available for severe environments.
Specifications
Tolerance: 5%
Maximum Harmonic Distortion: 1%
Power Factor: .05
Insulation: 220°C
Cooling: Air
Branch Circuit Fuse Protection
of page |
Simplex Branch Circuit Fuses
Cooling Systems
of page |
Natural Convection Air Systems may be used up to a 20 KW maximum.
Integral Fan Forced Air Systems for resistive load elements consist of an aluminum fan blade (shrouded for high efficiency) directly driven or belt driven by a motor. The fan motor is energized by a control contactor and protected by a circuit breaker. Motors for outdoor Load Banks are totally enclosed. Motors for indoor Load Banks are open-drip-proof.
Reactive Load Banks (inductive or capacitive) utilize a system which consists of fan shutter assemblies.
Resistive Load Bank Cooling Fan and Motor
Reactive Load Bank
Water Flow Systems consist of one or more water-cooled load modules supplied via an open loop water system. The pump/motor set delivers water to the load module.
Design Profile
of page |
Applications
Load Banks are used with Engine Generators, Battery Systems, UPS Systems, Inverters, Ground Power Units, Auxiliary Power Units, Aircraft Power Generators, Wind Generators, and Hydro Generators. Load Banks are used to test, prove and maintain AC or DC generators and power supplies.
Purpose
Test
- Test Load Banks are precision testing instruments which apply
discrete, selectable electrical load to a power generator while
measuring the response of the generator to the applied load.
Measurements of response stability and endurance can be made
and corresponding calibrations and adjustment can be effected
while a precise load is maintained on the power source.
Exercise - Exercise Load Banks assure the long term reliability
and readiness of standby generators by providing a means for
routine maintenance exercise of the generator under load. Exercise
Load Banks eliminate the detrimental effects of unloaded operation
of diesel engine generators.
Demonstration - A sophisticated engineering tool for demonstrating
product performance and capability to buyers and users and for
fulfilling contractual performance specifications
Type
Resistive - Dissipates energy output of generator and prime mover as heat. Unity power factor loading of generator. KVA load applied to generator equals KW load applied to prime mover. Provides equivalent of commercial lighting, heating loads
Inductive - Used in parallel with resistive Load
Bank to obtain lagging power factor, increase KVA load on generator;
does not increase KW load on prime mover. Provides equivalent
of commercial motor, transformer loads
Capacitive - Used in parallel with resistive Load Bank to
obtain leading power factor, increases KVA load on generator;
does not increase KW load on prime mover. Provides equivalent
of commercial electronic, fluorescent light loads
Capacity
Single Block - Entire capacity of Load Bank applied,
on/off, in one step increment
Multiple Steps - Load Bank capacity is divided into discrete
increments for application in steps; defined in terms of load
step resolution, which is the smallest step increment of load
control. Steps can be coarse (50%, 33%, 25%) or fine (5KW, 1KW)
Single Voltage - Designed for a specific voltage, typical
of exercise Load Banks to 15KV.
Multiple Voltage - Capable of dual or quad voltages. Typical
of test systems. (Typical voltages—60HZ: 120/240, 208-240,
416-480; 50HZ: 190-220, 380-420; DC: 12-60, 125, 250) to 15KV.
Single Frequency - Designed for a specific frequency
Multiple Frequency - Capable of multiple frequency or
AC/DC operation (Typical frequencies: 50-60-400HZ, DC)
Cooling
Natural Convection Air - 20 KW Maximum
Integral Fan - Cooling fan included in Load Bank; up to
3000 KW.
Radiator Airflow - Load Bank installed in radiator fan
airflow; up to 1000 KW
Water - Cooling via heat transfer to water flow; water
does not conduct electrical current. Open flow using commercial/natural
water or closed loop using heat exchanger up to 1200 KW.
Enclosure
Portable - For factory, shop, field use, self-contained
Stationary - For permanent installation at a specific
site
Duct Mounting - For permanent installation in radiator
airflow
Indoor - NEMA-1 enclosures
Outdoor - NEMA-3R enclosures
Control
Local
- Control panel self-contained in Load Bank
Remote - Control panel for remote operation
Automatic - Wide variety of auto control available including
auto on-off, auto load regulation, KW or reverse power response,
computer control
Connection
Cable Set - Connection cable included with Load
Bank. Typical of portable units
Terminal Block - Power terminals for connection of building
cables. Typical of stationary and duct mounted units.
Plugs - To match commercial wiring devices, aircraft plugs,
MIL-SPEC plugs, cam-lock connections.
Features
Short Circuit Protection - Load element branch circuit fuse
or circuit breaker protection
System Protection - Protected against running failures
(fan fail, over temperature, over voltage, etc.)
Control - Self-contained load control devices (contactors,
relays, circuit breakers)
Handling - Forklift channels, lifting eyes, casters on
portable units.
Instrumentation - Full instrumentation available: analog
or digital; data acquisition systems
Options - Many options available
