Load Bank Elements - What's the Difference?
The type of resistive element used in load bank construction depends on the manufacturer and the load test application. Below describes common types of resistive elements with the benefits and potential drawbacks.
These elements provide a very high watt density in a small diameter. The elements are “open wound” (require no internal ceramic core) which reduce weight and increase kW capacity within the load bank enclosure. This allows for high capacity loading, in a small lightweight package. These elements are used in a variety of portable, permanent, radiator and trailer mounted load bank applications.
Avtron 1000, 2000, 4000, 5000, 7000 and 9000 series load banks configure these elements in a helical design to provide sufficient cooling of the elements, and to allow no cool-down period after use. The requirement for slightly larger airflow to cool the high watt density elements requires the use of multi-prop fan blades. The increased props add to the acoustic levels of the equipment.
- High kW density in smaller space thus reducing the size of the load bank.
- Low weight making the smaller load banks easier to lift and move.
- No cool down period required once load test is complete.
- High watt density open wound resistors create significant thermal output.
- Multi prop fans produce high acoustic levels.
- Open Wound design requires additional ceramic insulators and stainless steel rod support.
A sheathed resistive element is constructed in a ‘u’ shape configuration. It consists of an inner and outer sheath. The inner heating element is compacted in magnesium oxide powder providing good thermal and insulation properties. The outer sheath is stainless steel to prevent corrosion. Sheathed elements typically don’t reach the same high temperatures that other elements types do, prolonging lifespans with continuous operation. Furthermore, because of the lower operating temperatures, less airflow is required from the fan to cool the elements thus reducing the acoustic levels. Load banks using sheathed elements are perfectly suited for heavy-duty load test applications due to the enhanced reliability in varied climatic conditions. Sheathed non-finned elements are used in Avtron 3000, 6000 & 8000 series load banks.
- Very durable in heavy duty applications.
- Insulated meaning water, dirt and debris can flow over without any adverse effects on the load test.
- Not live reducing the possibility of short circuit.
- Less fan speed to cool elements reducing noise levels.
- Larger and heavier than open wound elements generally meaning a larger sized load bank enclosure for the same kW value.
- A cool down period is often required after use the dissipate residual heat in the elements.
Sheathed, finned elements are a similar configuration to sheathed non-finned elements but utilise extra fins around the element to increase the resistance. This means in the same area as non-finned elements the finned element may provide a higher kW value. Finned sheathed elements, however, tend to need replacing more often due to hot spots. Hot spots can be caused by debris being caught in the fins or the fins becoming loose from the sheath over time due to element temperature fluctuations. The hot spots can cause overheating and reduce the operational life of the element.
- Less elements to achieve equivalent kW as sheathed elements.
- The fins tend to get hot spots reducing operational life.
- Higher airflow is required to cool the elements which increases the acoustic levels.
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