Altitude De-rating

Altitude range for the Unidrive M -> 0 to 3,000 m (9,900 ft), subject to the following conditions:

• 1,000 m to 3,000 m (3,300 ft to 9,900 ft) above sea level: de-rate the maximum output current from
  the specified figure by 1% per 100 m (330 ft) above 1,000 m (3,300 ft)
  Example at 3,000 m (9,900 ft) the output current of the drive would have to be de-rated by 20 %

The drive is rated for 0 to 3000m (9,900 ft) above sea level. For us to go above this level we need to consider the following 2 things:
1.) The effect on drive cooling. Due to the air being thinner.

2.) Creepage and clearance. Clearance is the shortest distance between two conductive parts. Our drives are designed with spacings between conductive parts that are sufficient to ensure user safety in the presence of hazardous transient over-voltages. Altitude with reference to sea level affects the required
clearance. The higher the drive the lower atmospheric pressure. Basically there is less resistance to breakdown at higher altitudes.

Our advice is as follows:

1.) We would advise to continue derating the output current on the drive by 1% per 100m (330 ft) after 3000m (9,900 ft) above sea level. The output current will already be de-rated by 20% at 3000m (9,900 ft).

2.) If the customer is planning to install the drive above 3000m (9,900 ft) which is beyond the specification of the drive, we advise that the customer uses additional voltage suppression up stream of the drive. In order to meet the requirements of the safety standard IEC 61800-5-1 and protect the drive up to
8000m (26246 ft) it is necessary to provide upstream transient surge suppression (TVSS) to limit over voltage transients to 2.5kV. Transients should be limited both line-to-ground and line-to-line. TVSS (Transient voltage surge suppression) devices/modules will help protect the drive from seeing large
voltage spikes resulting from lightning strikes.

Examples
The Memshield 2 TVSS Range (M2SSK3) [http://www.memonline.com/memtvss.html].
The Merlin Gerin Multi 9 SPD (Surge Protective Device) Series [http://ecatalog.squared.com/techlib].
The Phoenix Contact FLASHTRAB compact (Surge Protection Device) [http://eshop.phoenixcontact.co.uk].