For example, Cressall’s EV2 resistor, when operating at 0.22 bar as a single module has a power rating of around 5 kW when operating at a temperature of 10ºC, compared to 7.5 kW at a temperature of 14°C. Choosing a resistor that meets the required power and resistance rating is essential. If the power passed through the resistor exceeds its rating at any given time, both the resistor and connected machinery could become damaged, which could be very costly and cause dangerous faults. Resistors with an insufficient power rating may become overloaded, carrying a risk of fire, which is extremely dangerous on ships. In addition to damaging the ship structure, the confined space makes it immediately dangerous for workers and equipment on board the vessel. On the flipside, resistors with higher power ratings are typically made of more expensive materials, meaning the cost of the resistor is higher.
Size and weight
Cressall has the expertise to produce bespoke resistors, specifically designed to meet electrical needs while fitting into tight areas. Space is often particularly restricted in ship machine and engine rooms, where resistors are usually installed, so small off-the-shelf resistor solutions are often installed. For some situations, such as braking resistors used on thrusters, a small compact resistor with a comparatively low power rating is the perfect fit. This is why, in addition to its bespoke resistor capabilities, Cressall has produced the EV2 range of advanced modular watercooled resistors. Able to operate as a single module, or a combined unit, the EV2’s 25kW continuous rating means power input can range from 10kW to over 1MW, while remaining space-efficient. Choosing the correct resistor is essential to ensure productivity is as high as possible, by meeting the specific requirements of the project alongside demands of the ship.
About the author:
David Atkins is project director at power resistor manufacturer Cressall - www.cressall.com