Page 4 - SOS Catalog
P. 4

Fundamentals


               of Load Bank Rentals • Page 2




               Load Bank Testing of Electrical     Load Test Capacity                  Low Power Factor Testing
               Power Sources                       The desired capacity of the load test is   By adding an inductive load to the resistive
               Any device which generates electricity   expressed in kilowatts (KW). KW corresponds   load, lagging power factor can be obtained.
               may require load testing. This can be for   directly to engine HP (.746 HP = KW) and   Commercial loads, as well as generator sets,
               product development, production line testing,   is developed exclusively by the resistive   are rated at the nominal power factor of 0.8
               product demonstration, commissioning of   load bank. Adding reactive load changes the   lagging. This number is the cosine of the
               a new installation or for periodic service,   total KVA of the load, but does not alter the   angle made between the KW and the KVA in
               maintenance or trouble shooting. Although   KW or HP load. A purely resistive load bank   the diagram below:
               the most common use of load banks for   provides a realistic and effective test of the
               testing is with engine generator sets, in fact,   prime mover and causes full load currents to   kVA
               any device which generates electricity may   be developed by the generator. The engine
               require a load bank for testing, service or   will develop full rated HP, operating pressures   kVAR
               calibration. This includes UPS, batteries,   and temperatures, and the performance of
               power supplies, fuel cells, solar cells, wind   the governor will be fully evaluated. Adding
               turbines, hydro generators, etc. A load bank   inductive load allows for the full KVA capacity   kW
               provides a stable, known, controllable and   of the generator to be developed for a full
               relatively “harmless” load for these purposes.   functional test of temperature rise, waveform   COS  = Power Factor
               That is, if the performance of the generator   quality, voltage regulator response and   KW
               is not known, it is better to evaluate the   reactive load sharing.             PF =  KVA
               performance with a load bank than with
               critical facility loads.            Voltage                                     TAN  x KW=KVAR
                                                   Low voltage AC systems are rated 120/240v,   KVA=  KW +KVAR 2
                                                                                                        2
               Load Bank Overview                  single-phase, 2 or 3 wire; 208-240/416-
               Load banks simulate the “real world” loads   480/575-600/690vAC, 3 or 4 wire. Medium   The magnitude of inductive load required
               that the power source will experience.   voltage systems are in the 5kV or 15kV class.   to obtain 0.8 power factor is 0.75 X the KW
               Electrical load can be broadly classified as   DC systems can range from battery voltages   (1000kw + 750kvar = 1250kva at 0.8 lagging
               resistive, magnetic and capacitive. In the   of 12/24/32v, 125/250v, or 350/700v, typically.   power factor). As a point of interest, 0.75 is
               real world, these components are mixed,   Keep in mind that the AC load banks in this   the tangent of the aforementioned angle.
               as they are with a load bank, except with   catalog are generally 3-phase, 3-wire loads,   Keep in mind when sizing cables that the
               the load bank, full control of the component   meaning that a neutral is not required and   full load current at the rated KVA must be
               loads is possible. Resistive loads comprise   that loads are applied in 3-phase balanced   calculated.
               incandescent lighting, electric heating and   steps
               other loads in which electrical energy is                               Leading Power Factor Testing
               largely converted to heat. Magnetic loads   Current                     The same rationale as above applies to
               comprise motors, and other devices which   Current, expressed in amperes, is found by   leading power factor, except capacitive load
               convert electrical energy to mechanical   the following formula:        is added. Leading power factor testing is
               force and transformers which “step-up”                                  rare and specialized. Most engine generator
               / “step-down” power from transmission               KWx 1000            sets cannot tolerate more than a very small
               to utilization voltages. Capacitive loads   3ph. A=                     degree of leading power factor.
               comprise electronic loads. Although both AC      (Vx 1.73xP.F.)
               and DC systems power similar loads, most                                Portability and Site Conditions
               of this discussion will involve AC systems.   Current must be known in order to size
               The most common load bank and the load   connection cables. Keep in mind that   When designing a load bank rental,
               bank which is suitable for general load   connection cables have a certain small   considerations must be given to site space,
               testing is the resistive load bank. A resistive   resistance, and that a small voltage drop   access and set up. All SOS Rental Load
               load bank converts electrical energy to heat.   will be seen across the cable set and at   Banks listed herein can be networked in
               Within the load bank, the load is divided   the terminals of the load bank. Therefore,   groups and connected in parallel to provide
               into discrete circuits or “steps” capable of   although the generator instrumentation may   a total, aggregate load. It may be more
               stepwise, controlled application. The load   indicate 480v, the load bank instrumentation   workable to network 10 SOS Powerstar Load
               bank includes a means of cooling, most   will measure the terminal voltage at the load   Banks to obtain 1000kw than rent a single
               commonly forced air, but also water. The   bank, for example, 473v.     1000kw Load Bank.
               load bank also includes protective sensors,
               circuit protection devices, instrumentation, an   KW as a Function of Voltage  Networking and Paralleling
               operator interface and a means of connection                            Most SOS Rental Load Banks can be
               to the generator. To simulate magnetic or   KW varies as the square of the voltage:     networked and paralleled to form larger
               motor loads, an inductive load bank is added   therefore, in the preceding example, if the   systems. Powerstar and Infinity Load Banks
               to the resistive load bank. This can take the   load bank terminal voltage is reduced to   can only be networked with other Powerstar
               form of an integrated, all-in-one package, or   473v, then the resultant KW will be 97% of   and Infinity Load Banks. All other digital
               separate units. Likewise, a capacitive load   the rated KW. Where did that power go? It is   models can be networked and paralleled
               bank can be added. Inductive and capacitive   lost as heat in the connection cables.   in any mix and match combination up to
               load banks are always used in conjunction                               a maximum number of units. All control is
               with a resistive load bank-- there is generally                         centralized in a single operator interface.
               no reason to use one alone. Inductive and                               All data is likewise totalized to the operator
               capacitive load banks, also known collectively                          interface. Networking is via data cables
               as “reactive” load banks, are only used on                              provided with the load banks. Power cables
               AC systems and result in lagging or leading                             are paralleled to the power source.
               power factor for inductive or capacitive loads
               respectively.


               SIMPLEX ONSITE INC.                                                      © 2017 Simplex Onsite, Inc.  All Rights Reserved.
               simplexonsite.com  • 855-SOS-LIVE  • 855-767-5483                        Printed in the USA  •  1606-12.03
               Rental Centers: Springfield, IL; Atlanta; Baltimore; Boston; Denver; Houston; Minneapolis  Design subject to change without notice.




          SOS-Catalog-Cover-1606-12.02.indd   4                                                                     10/28/2016   8:49:00 AM
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