Dynamic braking for marine and offshore electrical drives
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.
Advantages of electric braking
An important benefit from using an electric drive is that reliable systems of regenerative and dynamic braking resistors are available to complement or replace traditional mechanical braking systems. The advantages of electric braking include control, reliability, mechanical simplicity, weight saving and in some cases the opportunity to make use of the regenerated braking energy.
Cressall Resistors’ wide range of resistor technologies and long experience in this field means that we have suitable brake resistor designs for all of the above applications, with braking powers from a few kW up to many MW (needed, for example, for some crane and main propulsion brakes) and cooling methods which include liquid, forced air and natural convection. We have standard products of all types.
The majority of our designs make use of suitably rated Incoloy-sheathed mineral insulated elements. These are less vulnerable to physical damage, prevent accidental contact with live, possibly high voltages, and are thus considered much safer to use in these environments.
For brake resistors operating at more than 2kV, sheathed elements are unsuitable and we employ live elements. Normally, cooling is by simple natural convection, but if the heat losses after braking would impose unacceptable loads on the ship’s air conditioning system we add an air-to-water heat exchanger to transfer the brake energy to the ship’s chilled water system.