A quick-fire guide to choosing the right power testing solution

If you’re in the market for a load bank, you’ll undoubtedly have come across the terms resistive and reactive. To make load bank specification as simple as possible, you need to understand the difference between the different types of load testing solutions and which one is most appropriate for your application. 

What is a resistive load bank?

A resistive load bank provides a simulated electrical load for generators and backup power systems. For engine-only exercising and general engine maintenance, a resistive-only loadbank is ideal for clearing carbon build-up in the engine, it is the most common and cost-effective option for preventative maintenance.

What does a resistive load bank do? 

A resistive load bank mimics the operational load that a power source would handle during actual use. When used as a controlled system test, the load simulates real-life resistive loads, such as incandescent lighting and heating loads, as well as the resistive or unity power factor component of magnetic (motors, transformers) loads. A resistive load bank works by converting electrical energy into heat using power resistors, which then dissipate the heat using forced air cooling. 

What applications use a resistive load bank? 

Resistive load banks can be used for a broad spectrum of applications, from testing turbines, rotary UPS and generators in sectors like heavy industry, and manufacturing, as well as for maintenance in mission-critical facilities like hospitals and data centres. 

Is a resistive load bank sufficient to completely test my system? 

It is important to note that, in many applications, resistive loads make up a small proportion of power consumption. In data centres, for example, it is generally only heating and lighting systems that use a resistive-only load. Alongside this, other aspects of the operation incur reactive loads; these create a lagging power factor (pf), typically around 0.8, which is not accounted for when undertaking a solely resistive test. 

What is a reactive load bank? 

Reactive load banks do not test a system at full load. Instead, they simulate “real world” scenarios for either an inductive or capacitive load – whichever is relevant for the application. They use a 0.8 power factor with a 75% load, compared to the 1.0 power factor and 100% load of a resistive loadbank. A reactive load bank works by converting current into a magnetic field and can resist the change to voltage, which causes the circuit current to lead voltage.

What type of applications use a reactive load bank? 

Reactive load banks can be used to evaluate transient loads, as well as for load sharing and testing alternator capacity. This type of testing is suitable for equipment that is affected by electric motors or other electromagnetic devices. This could include applications like motor-driven devices, transformers and capacitors, making them a real contender for the telecommunications, solar, manufacturing and mining industries. 

What is a resistive/reactive load bank? 

These solutions combine both resistive and reactive elements in one load bank. The system can also be switched to enable resistive only, inductive or lagging power factor testing. 

The inductive loads used in resistive/reactive testing will show how a system will cope with a voltage drop in its regulator. This is particularly important in any application which requires generators to be operated in parallel (e. larger business infrastructures such as major telecoms or data centres) where a problem with one generator could prevent other system generators from working as they should. This is something which is simply not achievable with resistive-only testing. 

Why is a resistive/reactive load bank the best choice?

A resistive/reactive load bank can be used to test a generator fully at 100% nameplate kVA rating. Carrying out this type of load bank testing provides a picture of how well an entire system will withstand changes in load pattern while experiencing the level of power that would typically be encountered under real operational conditions. 

Ideally, all generators should at the very least be tested annually for real-world emergency conditions using a resistive-reactive 0.8pf loadbank. Where a resistive-only loadbank is used (1.0pf), testing should be increased in frequency to ensure that the system doesn’t encounter issues when an emergency arises. 

What is a DC load bank? 

In addition to the main categories of loadbank listed above, DC load banks can be used to provide an accurate load for the discharge of batteries, both following amps and voltage, from 24VDC to 700VDC, with power from 10kW to 664kW. 

Why use a load bank: Key benefits

Load testing a generator offers reassurance 

Crucially. testing a backup power system at full load provides reassurance that, even in a worst-case scenario, the generator is able to perform under the most demanding conditions. Regular load testing can increase the life and reliability of a generator. 

Load bank testing helps to prevent wet stacking 

Unburned fuel inside a backup generator can clog the exhaust system and result in excessive moisture in the engine – this is called wet stacking. Using a load bank to apply a full load to the generator encourages the engine to burn more fuel, preventing wet stacking. 

If wet stacking conditions are already present, the load bank testing process will burn off the excess moisture, improving engine performance and prolonging system life. 

Treatment of exhaust fumes

Using load bank testing to force a generator to operate at full load will exercise the exhaust system enough to improve peak performance.

Identify hotspots and component performance issues

Applying reactive load conditions to systems in parallel presents an ideal opportunity to assess the performance of electrical connections, cables, bus work and other components. Likewise, where possible, infrared can be used during the testing phase to identify system hotspots. 

Take the first steps towards effective backup power testing

For more specific support on choosing which loadbank is right for your application, speak to our specialist team today on 01283 531 645 or email sales@crestchic.com.

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