Installing AC drives at low temperatures
Here in the UK the weather is a constant source of conversation and consternation. Complaints of its too wet, too cold or even it's too hot are year round. Yet despite our obsession with the weather we live in a relatively temperate climate. Thanks to the Gulf Stream we enjoy favourable conditions for most of the year. That's despite London lying further north than all major Canadian cities including; Vancouver, Montreal, Quebec City, and Toronto. So, with temperatures in the UK rarely falling below -10 °C, Brits can hardly claim to experience the regular -10.5 to −9 °C winter lows normal to Montreal.
When installing AC Drives when should we be concerned about cold weather?
Within your AC drive's installation guide there should be an indication of minimum and maximum operating temperature ranges. Usually the bottom range would be -10 °C. Within this guide you would also find a minimum storage temperature. For some products this will allow storage as low as -40°C. A further consideration should be whether the drive can operate at full capacity. Most drives will not operate at full capacity at very low temperatures, so will need to be derated.
What happens to an AC drive at low temperatures?
- LCD Display
Most AC drives are fitted with a liquid crystal display (LCD). As the temperature drops there's and increased risk of the liquid within the display freezing. As the display cools it will slow down, then as the temperature drops even further and the display freezes all functionality will be lost.
- Electrolytic Capacitors
The Equivalent Series Resistance (ESR) of the electrolytic capacitors within the drive are also affected by temperature. The resistivity of the electrolyte increases at low temperature. The result for the capacitors is a loss of torque and an increase in DC ripple voltage which can result in damage to the AC drive.
- Potted Components
In extremely low temperatures potted components can crack and severely affect the lifespan of the drive.
How to mitigate the effects of low temperature
For other applications which are more process driven such as cranes and hoist the drive will run less frequently. For applications such as pumps and fans which aren't always running and do not always run at full speed a large amount of heating would be necessary. If these operations are critical it would be prudent to run them at a constant low temperature to guarantee optimal functionality.
To avoid any or all of the above negative effects of low temperature on your DC drive it's really important to consider a way to combat the cold.
External heating could be considered dependant on the operating profile of your AC drive. In some applications, if the AC drive operates constantly within an enclosure, external heating won't need be a consideration. The heat emitted by the drive and other devices would be enough to generate an ambient temperature.
Or, if the drive operates in the open air then temperature is impossible to regulate. In this case there are options such as the VACON® 100 X . This is a temperature controlled heating option which can be integrated into the drive itself.
What other factors should be considered at low temperatures?
The solutions above are simple. They just require the installer to pay serious attention to the environment in which the AC drive operates.
Heating an AC drive within an enclosure will negate the effects of the cold but will do little to guard against water vapour. Even if your AC drive is IP66/UL Type 4 rated it is difficult to guard against water vapour. As pressures inside and outside of the unit equalises, water vapour from outside of the unit will enter. At low temperature, the obvious risk would be for the water vapour to freeze and cause frost damage.
A dehumidifier could mitigate some of the risk posed by water vapour. There are products available which can filter moisture from the unit as external air enters the drive. Leading drive manufacturer Danfoss includes a GORE® Vent in the VACON® 100 X, VACON® 20 X and VLT® Decentral Drive FCD 302. These parts are manufactured using a breathable substance designed to filter moisture from the air.
If you are at all unsure about how to install your AC drive and what to consider at low temperature then Northern Industrial is here to help. Our expert engineers have over 40 years of experience working with industrial automation products from all major brands. With customers around the world we are sure to have advised on the best method for your drive and the environment it will operate in.