High-performance dynamic braking resistors feature low noise

Paul Boughton
Cressall Resistors is introducing its HP series of high-performance dynamic braking resistors (DBRs). The new range is suitable for use on cranes, winches, conveyors and test loads, as well as on lifts and elevators.
Compact and ready boxed, these DBRs are protected to IP20 and make virtually no noise when subject to inverter braking currents. The low-inductance, open-wound element construction allows high power dissipation in a small space. It is these two factors that make the HP series attractive for use in lifts and elevators, where noise and heat dissipation are both significant issues. When used with an inverter, the units are suitable for use with any make of drive.
The range is divided into HP1, HP2 and HP3 units, which have continuous power ratings of 1.5kW, 3.0kW and 4.5kW, respectively. The continuous power ratings can be exceeded when power is applied for less than 100 per cent of the time and the extent to which this can be done is calculated using a simple equation.
All of the resistors are manufactured using high-grade nickel-chrome wire, the resistance values of which change very little over the temperature range of the element. As a result, the units are much more effective than versions produced with other materials, such as lower-grade stainless steels, for instance.
The robust units measure just 508mm in length by 140mm high and between 144mm and 239mm wide, depending on the model chosen. The larger models offer higher continuous power ratings. They can be provided with an IP21 drip-proof canopy if required, although this will increase the height and overhang of the unit. A knock-out hole for cable entry is provided on each outward facing side and on the bottom of the terminal compartment.
For more information, visit www.cressall.com

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