Brake Resistor for variable speed drives, inverters and VSDs | HVAC | Automation

Power quality expert, REO (UK) has launched a new braking resistor incorporating a component mounting surface. The novel design of the BW156.9 range will free up installation space for mounted components used with motors and variable speed drives (VSDs). At the same time, a higher ingress protection (IP) rating and forced cooling will provide better power efficiency and increase safety.

Growing complexity in the industrial sector over the last few years has made it increasingly difficult to design applications that maximise the efficient use of space and power whilst ensuring that equipment is safe and reliable to use. This problem was highlighted recently, when the IET (The Institution of Engineering and Technology) proposed changes to the Eco Design Directive being drafted as part of EU legislation.

“Better use of the available installation space can drastically affect the performance of components,” explained Steve Hughes, managing director of REO. “We originally developed the unique mounting system for a leading drive manufacturer in the building technology, heating and ventilation (HVAC) sector. However, for the past two years, the design has been under embargo.

“The launch of the BW156.9 fulfils two core needs. Firstly, components can be mounted on the panel housing the braking resistor. Secondly, this moves the potentially hot resistor away from engineers working on the panel and reduces the requirements for additional guarding,” said Steve.

“The resistors can be locally force cooled, which increases their power rating by 20%. By default, the units are rated for 900V and can be supplied with variants from 200W to 30,000W and in resistance values from 1 to 2000R,” continued Steve.

A wider trend in the industry has seen VSDs increasingly used with HVAC (Heating, Ventilation and Air Conditioning) and pumping applications. In these situations, prolonged exposure to dust can cause significant damage to equipment. To tackle this, the new braking resistor series is protected with an IP20 rating as standard and can be supplied up to IP64. This means that the units can be used in areas without control housings.

“We did face some design challenges in developing this unit,” explained Steve. “The key point was ensuring that the heat from the resistor is not transferred to the mounting surface. We were able to overcome this issue by using insulated standoffs to isolate the panel from the resistor and ensure that anything mounted doesn’t get hot,” said Steve.


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