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How severe conditions can affect variable-speed drives

The variety of electric motor-powered applications that benefit from variable-speed drive installation means that VSDs can be found in some extreme environments. Here we look at the challenges faced by users in maintaining effective and reliable variable-speed drive performance in extreme conditions.

Low temperatures

All drives come with a minimum operating temperature as designated by the manufacturer, which is typically set at around -10°C. The threshold during transportation and storage tends to be much lower – roughly -40°C.

Many VSDs include an LCD (liquid crystal display) for the control panel screen, and at low temperatures these may not refresh contents as quickly. Should the temperature become too low, the liquid crystal will freeze and the display will become inoperative.

Low temperatures can also cause electrolytic capacitors to become less effective, leading to starting torque losses. In extremely low temperatures, components can become brittle and crack which significantly reduces the drive’s operational life.

High temperatures

VSDs can normally be transported and stored in ambient temperatures of up to around 70°C, but once they are put into operation, the recommended limit is usually about 50°C.

Extremely high temperatures aren’t only a consideration when a VSD is used in an extreme climate, such as a desert, a drive here in Britain could be exposed to severe heat depending on the ventilation within the room in which they are located.

If a VSD is stored in direct sunlight, capacitors can be damaged due to rising internal temperatures which quickens the components’ normal ageing process.

Long-term exposure to excessive heat during operation also shortens the lifetime of drive components, which can be alleviated by limiting output current to the electric motor as temperature increases.

High altitudes

At high altitudes, air density becomes lower. This reduces the cooling capacity of the air which creates a problem for indoor drive installations.

Most drives can operate to specification at up to 1,000 metres, above which they may need to be derated (operated below the rated maximum capacity) in order to avoid overheating and subsequent damage to components.

Normal drive capacity may still be achieved by introducing artificial cooling via fans.

Ingress of solids and liquids

Certain applications, such as food and beverage production and mining, expose VSDs to liquids and solids. This may be due to anything from high-pressure wash-down systems used for cleaning equipment to airborne dust particles.

Ingress Protection (IP) ratings are used to grade a VSD’s resistance to solids (ranging from any large surface of the body to dust tightness) and liquids (ranging from dripping water to powerful high-temperature water jets).

When placing an order for a drive, the user must select the appropriate IP rating to ensure adequate protection.

If you have a requirement for variable-speed drives, no matter what the operating conditions, Gibbons is here to provide expert assistance. As an Authorized Value Provider, we’re approved to supply, install and offer associated services for ABB drives. For more information, call Alan Roberts on 07966 468430 or email alan@gibbonsgroup.co.uk

Variable-Speed Drives, Electric Motors

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