Cressall products

For high current ratings the most suitable earthing resistor element is the type RP oval edge-wound coil. RP resistors are manufactured from a continuous stainless steel strip, wound edgewise into oval coils. Each coil is supported by ridged ceramic insulators mounted on a stainless steel centre support, with stainless steel terminals welded at each end. This arrangement allows free expansion and contraction at operating temperatures up to 1000°C without imposing strain on the assembly.

For medium current ratings (30-100A) the HPR grid is used; this is a versatile, robust construction with a high ratio of surface area to active mass and can be manufactured in a very wide range of resistor materials.

For low currents the most suitable elements are the coiled-coil, type HP, which has a compact construction, excellent overload rating and good shock resistance.

The preferred enclosure material is unpainted stainless steel (either 304 or 316). This has good long-term corrosion, damage and heat resistance levels. We can also offer mild steel, hot dipped galvanised or pre-galvanised and all these options can be painted.

Load Banks for standby generators and uninterruptible power supplies. Cressall’s medium-voltage load banks installed in central London, act as test and exercise loads for standby generators and uninterruptible power supplies. These were challenging installations because the specification required the loads to add no additional noise to that from the generating sets themselves.

The infrequency of power outages in most developed countries, and the rarity with which standby sets are called on to run ‘for real’, make regular proving essential if sets are to operate reliably when needed. In recent years, blackouts in Europe and the U.S. will have been an uncomfortable reminder of this to the many organisations who did have standby generators that failed to work on the day.

Electrical drive systems are being used more and more on ships, oil rigs, crane barges and offshore vessels of all types, for every type of powered application: main propellors and electric bow thrusters, driving winches and windlasses, cranes, lifts, conveyors and jacks, cable laying and tensioning.

Most ships have a chilled water system, which circulates cool water throughout the vessel, used for both air conditioning and equipment cooling. It is usually straightforward to incorporate resistors of the type shown into these circuits.

A new range of water cooled resistors for low and medium voltage applications, especially severe conditions in marine systems. Rheostatic braking of all types of low and medium voltage AC drives in:

Cressall’s standard ranges of high capacity dynamic braking resistors (DBRs) for regenerative and rheostatic electric motor braking are low cost, easy to specify, quick to install and with ratings to suit inverter drives of any power. Our wide range of resistor technologies means that we can select the most technically appropriate and cost-effective resistor design for any application, whether continuous, intermittent or infrequent.