Neometrix / Load Banks / Load Bank / NMX-LBK-57

NMX-LBK-57 · ENGINEERED-TO-ORDER CLASS — SPECIFY · CONNECT · STEP · HOLD · REJECT · PROVE

Load Bank. Real power is not the whole load.

Name: Load Bank
Brand: Neometrix
SKU: NMX-LBK-57

A resistive load bank fills the engine of a generating set, but not its alternator. It turns real power into heat and leaves out the reactive power that a real load also draws.

So the bank is built around three things: real and reactive steps, a DC section for batteries and supplies, and cooling that carries every watt away.

Discuss a load bank Capability note (PDF)

A single resistive load bank: a robust rectangular enclosure of grey painted steel on a heavy steel skid with fork-lift pockets, a galvanised wire-mesh air intake guard along one long side, a round axial cooling fan under a wire guard on the top, and at one end an open-fronted steel terminal box with thick black power cables ending in copper cable lugs bolted onto copper studs, and no people

Fig · 01 — A resistive load bank: one steel enclosure on a skid, with an air intake guard, a cooling fan on top and a terminal box with its cables — illustrative render.

The load

real and reactivestepped in and out

The DC

current or power heldfor batteries and supplies

The heat

carried awayby air or a closed water loop

The proof

held until it settlesthen the load is dropped at once

Status

engineered to orderno general-purpose bank claimed

ISO 9001ISO 14001ISO 8528-6 generating set test referenceIEEE 450 battery test reference

Overview

Why a load test must give the source the whole load it will see.

Because a generating set is rated in apparent power, and a resistive bank cannot load that. It fills the engine and leaves the alternator part empty.

Fig · 02 — The bank in one picture: it is connected to the source, loads it in steps, and carries every watt away as heat.

Real power is not the whole load.

What the bank is for

It gives a source something to push against. The bank is connected to a generating set, a battery, a UPS or a power supply, takes power from it in steps, and turns every watt into heat. It suits AC resistive, AC reactive and DC duty.

Why real power is not the whole load

A generating set is rated in apparent power, at a stated lagging power factor. A resistive load draws current in step with the voltage, so it is all real power. It can fill the engine, but the alternator is then carrying less current than its rating, and the reactive part of the duty is never tested.

Why a resistive bank is still useful

It loads the engine, its cooling, its fuel and its exhaust fully, and it is simple to run. For many acceptance tests the engine is what has to be proved, and a resistive bank proves it. What it cannot prove is the alternator at its rated power factor.

Why the reactive step is added

An inductive load takes reactive power from the set. The alternator has to carry that current, and the regulator has to hold the voltage against it. A bank that adds reactive steps to the resistive steps, in the right ratio, brings the set to its rated point, where the engine and the alternator are both full.

Why the DC bank is different

A battery or a DC supply is tested by holding the current, or the power, and watching the voltage fall. A constant-current bank holds the current as the voltage sags. A constant-power bank lets the current rise as the voltage falls, as a converter load does.

Why the load is stepped

Load is switched in and out in steps, and the whole load is dropped at once. Stepping shows how the governor and the voltage regulator respond. Dropping the load shows how far voltage and speed overshoot before they recover.

Why the heat is the design problem

Everything the bank absorbs becomes heat, so the cooling sets what the bank can do. If the heat cannot leave, the elements climb until the thermal trip stops the test.

The method

Specify, connect, step, hold, reject, and prove.

Six steps in a fixed order. The two shaded steps are the ones a quick order skips.

FIG · 02LOAD BANK · SPECIFY / CONNECT / STEP / HOLD / REJECT / PROVE — REAL POWER IS NOT THE WHOLE LOAD

The step people underrate is the reactive load. A set that has passed every real-power step has not been loaded at its rated power factor.

Fig · 03 — Three ways a load test lets you down: it is resistive only, it runs too light, and it cannot shed its heat — a drawing of the idea, with no values.

1 · Specify

The source, its rating, its power factor and the duty are stated by the customer, and the bank is sized to the real and the reactive load needed.

2 · Connect

The bank is joined with cable sized to the current, earthed and interlocked, so that the cooling must be running before any load is applied.

3 · Step

Load is applied in steps, real first and then reactive, up to the rating, with the readings taken at each step.

4 · Hold

The load is held until temperatures settle, so that a fault which only shows when the set is hot has time to show.

5 · Reject

The whole load is dropped at once, and the overshoot and the recovery of voltage and speed are recorded.

6 · Prove

The records are kept, and handed over with the set.

Work content

What the bank contains, element by element.

Read it as a checklist: a bank missing a row will pass a set that fails in service.

A single resistor element bank of a load bank with its side panel removed: rows of straight, evenly spaced, finned stainless steel tubular heating elements held between two grey steel frame plates, with white ceramic insulator bushings at the ends and copper links joining the element ends in groups, standing on a plain grey steel bench, and no people

Fig · 04 — The heart of the bank: rows of finned stainless steel resistor elements held between two frame plates — illustrative render.

Element	What it does	What matters
Resistor elements	turn power into heat	finned stainless steel tubes held clear of one another, that hold their resistance as they heat
Load steps	set the load	contactors or switches that bring groups of elements in, so the steps can make every load up to the rating
Reactive steps	add the reactive part	reactors in steps, switched in the right ratio to the resistive steps
DC section	loads batteries and supplies	elements and a controller that hold current, power or resistance as the voltage changes
Air cooling	removes the heat	a fan sized to the whole load, with the air path kept clear and the hot air discharged away from the intake
Water cooling	removes the heat in a loop	a closed water circuit with a heat exchanger, for places where hot air cannot be discharged
Controls	run the steps	manual selectors or a PLC, with step tables for the loads needed
Metering	reads the load	voltage, current and power read at the bank itself, so the load is known and not assumed
Protection	keeps the test safe	thermal trips, an airflow interlock, overcurrent protection and a means of isolation
Connections	join the bank to the source	cable terminals sized to the current, in a terminal box that keeps live parts covered
Enclosure	holds it together	a steel enclosure on a skid or trolley, with a guarded air intake and discharge
Procedure	fixes the sequence	specify, connect, step, hold, reject and prove, the same for every source
Testing & documentation	prove the bank first	a step check, an insulation check and a record the customer can inspect

The element that decides whether the test is true is the reactive step, because a bank without it can fill the engine but never the alternator.

Fig · 05 — One source, three kinds of load: resistive, reactive and DC, each read the same way.

Full specification — expand

System	Resistor elements; resistive load steps; reactive steps in the right ratio to the resistive steps; a DC section that holds current, power or resistance as the voltage changes; air cooling or a closed water loop; manual or PLC controls; metering at the bank; thermal trips, an airflow interlock and overcurrent protection; terminals and a terminal box that keeps live parts covered; a steel enclosure on a skid or trolley; a written test plan; and testing and documentation before handover
The One Idea	Real power is not the whole load.
Why Real Power Is Not The Whole Load	A generating set is rated in apparent power at a stated power factor, and a resistive load is all real power, so it can fill the engine but leaves the alternator carrying less current than its rating
Why A Resistive Bank Is Still Useful	It loads the engine, its cooling, fuel and exhaust fully and is simple to run, which is what many acceptance tests need to prove
Why The Reactive Step Is Added	An inductive load takes reactive power from the set, which the alternator carries as current and the regulator holds the voltage against, so adding reactive steps to the resistive steps brings the set to its rated point
Why The DC Bank Differs	A battery or a DC supply is tested by holding current, power or resistance while the voltage falls, and a constant-power bank lets the current rise as the voltage falls
Why The Load Is Stepped	Load is switched in and out in steps and the whole load is dropped at once, so the response and recovery of voltage and speed can be recorded
Why The Heat Is The Design Problem	Everything the bank absorbs becomes heat, so the cooling sets what the bank can do, and if the heat cannot leave the elements climb until the thermal trip stops the test
Standards	ISO 8528-6 is the public reference for the test methods of generating sets driven by reciprocating internal combustion engines, ISO 8528-5 for their transient performance, and IEEE 450 and IEC 60896 for testing stationary lead-acid batteries. This page prints none of their test loads or limits, and no edition year: those come from the standard the customer names and from the customer's duty. Approval of a source for use rests with the customer and the authority they name; none is claimed here
Configurations	A portable bank, air-cooled and moved to the source, a water-cooled bank with a closed water loop, and a programmed bank whose steps and profiles are run and logged by a PLC
Scope Boundary	This page is the general-purpose load bank. It is not the load bank for aviation ground power units and starter-generators (see aviation ground-power load bank), not a charger or rectifier, which is a source and not a load (see mobile rectifier and battery charger unit) and not a dynamometer, which loads an engine mechanically (see hydraulic dynamometer engine test cell). No certification is claimed here
Status	Neometrix has quoted against successive load bank requirements, and no delivered general-purpose load bank is claimed.

Configurations

One method, three ways to build the bank.

The method, the record and the settle rule are shared. What changes is how the heat leaves, and how much of the stepping is automated.

Portable bank

Elements, fan and controls

An air-cooled bank on a skid or trolley, moved to the source, with resistive and reactive steps set by hand and the readings taken at the bank.

Water-cooled bank

Elements, water loop and controls

A bank whose heat is carried away in a closed water loop, for places where hot air cannot be discharged or where the load is too large for air.

Programmed bank

Elements, PLC and logger

A bank whose steps, profiles and load rejections run from a stored sequence, with the readings logged for every test, and a DC section where batteries or supplies are in the duty.

Fig · 06 — Three ways to build the bank, one method: a portable bank, a water-cooled bank, or a programmed bank.

And the part that is not equipment at all, yet decides all three: the test plan. It fixes the load steps, the power factor, the time to settle and the date of the next test, and it is written from the source's duty, not from the bank.

Where it is used

Wherever a source has to be loaded, and proved at that load.

The common thread is a source that will be asked to deliver, and a test that has to give it the load it will really see.

Acceptance of generating sets

Where a new set is run at its rating, stepped and dropped, before it is accepted.

Commissioning and standby proof

Where a standby set is loaded on site, and again on a schedule, so that it is known to carry the load when it is called on.

Battery and UPS testing

Where a battery is discharged to an end point, or an uninterruptible supply is loaded, and the result is read and recorded.

Development and trials

Where a new supply or power converter is tried against a load that can be set, held and stepped.

Watch

See it in motion.

A short walkthrough video of the load bank.

FAQ

Common questions.

Longer answers, for readers who want the reasoning.

Q · 01 What does a load bank actually do?

It gives a source a load to work against. Connected to a generating set, a battery, a UPS or a power supply, it takes power in steps and turns all of it into heat, so the source can be run at the load it was designed for without waiting for a real load to appear. It does not generate, store or return power: everything it takes is lost as heat.

Q · 02 Why is real power not the whole load?

Because a generating set is rated in apparent power, and apparent power has two parts. Real power does the work and is what the engine supplies. Reactive power is drawn and returned by motors, transformers and other inductive loads, and the alternator has to carry its current. A resistive bank is all real power. It can fill the engine, but the alternator is then carrying less current than its rating, so what it was designed to carry has not been proved. For the usual rated power factor, the reactive part needed is three quarters of the real part, which is why a bank for that duty has reactive steps as well as resistive ones.

Q · 03 When is a resistive bank enough?

When the engine is what is being proved: its cooling, its fuel, its exhaust and its governor under full real load. A resistive bank is simpler to run, and it cannot pull the voltage down the way an inductive load can. It is not enough when the set will carry reactive load in service, or when the alternator, the regulator or a parallel arrangement is part of what has to be proved. The honest rule is to state in the test plan which of these the test covers.

Q · 04 How does a DC bank differ from an AC bank?

A DC bank is connected to a battery or a DC supply and holds the current, the power or the resistance while the voltage changes. For a battery capacity test the current is held, and the time taken to reach an end voltage is the result. A constant-power bank, which behaves as a converter or an inverter does, lets the current rise as the voltage falls. Which mode is used comes from the duty and from the standard the customer names. There is no reactive part in DC, so the questions that matter are how steadily the bank holds its setting and how it ends the test safely.

Q · 05 Is this the same as the aviation load bank, charger or dynamometer pages?

No, and the differences are worth stating precisely. The aviation ground-power load bank page is a resistive bank for ground power units and starter-generators. The mobile rectifier and battery charger unit page is a source of DC power, the opposite of a load. The hydraulic dynamometer engine test cell page loads an engine mechanically with a water brake, where a load bank loads a source electrically. A regenerative load, which returns the power to the supply instead of making heat, is a different machine again. This page is the general-purpose bank for generating sets, batteries and supplies. It does not replace any of them, and it does not claim what they claim a second time.

Q · 06 Has Neometrix built one of these?

We would rather answer this plainly than let a page imply otherwise. Neometrix has quoted against successive load bank requirements, and no delivered general-purpose load bank is claimed. What stands behind the offer is adjacent: Neometrix engineers a load bank for aviation ground power (see the aviation ground-power load bank page), DC power equipment (see the mobile rectifier and battery charger unit page) and test cells that absorb engine power (see the hydraulic dynamometer engine test cell page). The resistor elements, contactors, reactors, fans and meters are catalogue items, bought in, not invented. What Neometrix engineers is the bank around them: the enclosure and the air path, the step and switching arrangement, the cooling circuit, the controls and protection, the procedure and the record. So the honest position is that the bank is engineered to order, the neighbouring disciplines are in the building, and the first bank of this exact kind will be built around the customer's own source rather than taken off a shelf.

Q · 07 Which standards apply, and what can the bank not do?

ISO 8528-6 is the public reference for the test methods of generating sets driven by reciprocating internal combustion engines, and ISO 8528-5 for their transient performance. IEEE 450 and IEC 60896 are public references for testing stationary lead-acid batteries. This page prints none of their test loads or limits, and no edition year: those come from the standard the customer names and from the customer's duty. The bank loads a source and records what happens. It does not certify the source or anything else: this page claims no certification or accreditation. No power, current or temperature figure is printed here, and approval of a source for use rests with the customer and the authority they name; none is claimed here.

Q · 08 What do you need from us to quote?

Six things, and most of them describe your source rather than the bank. First, the source: its kind, its rating and its voltage. Second, the load needed: real and reactive, or DC, and the power factor. Third, the steps: how fine they must be, and whether they are set by hand or by a program. Fourth, the cooling: air or water, and where the heat can go. Fifth, the tests: stepping, holding and load rejection, and the standard you work to. Sixth, the record: what you want kept with each test. From that we come back with a bank concept, a written test plan you can check, and a budgetary price.

The neighbouring power-test pages, and how they differ from this one.

Three neighbours: one is an aviation load bank, one is a DC source, one loads an engine mechanically.

↗ An aviation load bank

Aviation Ground-Power Load Bank

A resistive bank for ground power units and starter-generators - one application of a load bank, with its own page.

↗ A DC source

Mobile Rectifier & Battery Charger Unit

A trailer-mounted DC power source - it supplies power where a load bank absorbs it.

↗ A mechanical load

Hydraulic Dynamometer Engine Test Cell

A water-brake test cell that loads an engine mechanically - the mechanical counterpart of an electrical bank.

Browse all Neometrix product lines.

Get a quotation

Tell us the source, the load,
and where the heat goes.

The projects desk replies within two working days with a bank concept, a written test plan you can check, and a budgetary quotation. Write to [email protected] or use the form.

Enquire — load bank Capability sheet (PDF) +91 7777 876 876

ISO 9001 / 14001 ENGINEERED-TO-ORDER CLASS — LOAD BANK SPECIFY · CONNECT · STEP · HOLD · REJECT · PROVE — REAL POWER IS NOT THE WHOLE LOAD ENGINEERED IN NOIDA · INDIA