New dv/dt chokes, designed for use on the output of modern frequency inverters and servo drives, have been introduced by Schaffner. The RWK 305 Series offers designers and operators reliable and cost-effective motor protection.

RWK 305 Series chokes are manufactured with an open-frame design, using vacuum impregnation to minimise humming. They are built with UL-rated materials and offer a variety of off-the-shelf ratings which can be readily adjusted to meet customer-specific requirements.

The innovative design of the RWK 305 Series ensures a longer, more reliable motor life. With a voltage drop of 0.8% uk, the new chokes reduce the dv/dt stress caused by the pulse width modulated (PWM) output signal of modern drives, protecting the motor windings and reducing harmonics inside the motor. Fewer magnetic losses in the motor means a lower operating temperature and a smoother signal in the motor cables causes less disturbance to neighbouring cables and equipment.

Ideal for use in servo drive applications, RWK 305 chokes cause no reduction in the control dynamic of the motor drive . The series also makes a cost-effective alternative to sinusoidal output filters in some applications, and is ideal for use in areas requiring short motor cables, from three to 30m.

Application potential is wide and diverse, including machine tools, wood-working machines, vacuum-pumps, laser technology, textile machines, elevators, robotics and a vast array of building automation.

The series is designed for an operating voltage of 3 x 400VAC and offers current ratings from 2.1A to 2300A @ 40C, in small incremental steps. They can be operated at motor frequencies of 50/60Hz and switching frequencies from two to 16kHz. Typical dv/dt reduction is a factor of five. The parts conform to EN 61558-2-20 and have a protection rating of IP00 / VBG4.

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