1.4.3 Installing the NEMA 3R Cover
1.
Set the NEMA 3R cover over the top of the frequency
converter. Align the NEMA 3R cover with the screw
holes on the top mounting plate and the screw holes
on the side of the unit.
2.
Using the 6 screws provided in the bag, loosely
secure the cover to the frequency converter.
3.
Torque all 6 screws to 2.3 Nm (20 in/lbs).
4.
Apply adhesive label to the cover. See
Illustration 1.5
.
NOTICE
REMOVING COVER
To remove the NEMA 3R cover after it has been installed,
remove the front 2 screws on the bottom of the unit. The
cover can be removed after the other 4 screws are loosened
since the cover has slotted screw openings.
1
Screw without captive washer
2
NEMA 3R sticker
3
NEMA 3R cover
4
Screws to remove for taking off the NEMA 3R cover
Illustration 1.5 Installing NEMA 3R Cover
1.4.4 Calculating Nominal Current when Using
a NEMA 3R Cover
The nominal current of a frequency converter with the NEMA
3R cover is 90% of its current rating. For example, in a
FC-302N250T5 standard IP54 frequency converter, the nominal
output current in normal overload mode is 588 A. With the
NEMA 3R cover, the normal overload current is 0.90 x 588 =
529.2 A. The same calculation is used to calculate the nominal
current for the high overload mode.
1.4.5 Derating for Ambient Temperature when
Using a NEMA 3R Cover
Using the NEMA 3R cover kit requires derating due to higher
ambient temperatures within the enclosure. Using SFAVM
(stator flux asynchronous vector modulation) gives greater
switching control, but generates more heat than using 60°
AVM (asynchronous vector modulation). SFAVM switches
throughout the entire cycle, where 60° AVM only switches 2/3
of the time.
The maximum switching frequency is 16 kHz for 60° AVM and
10 kHz for SFAVM. The discrete switching frequencies are
shown in
Illustration 1.6
.
Installation Instructions
NEMA-3R Cover Kit for D1h–D2h
VLT
®
FC Series FC 102, FC 103, FC 202, and FC 302
4
Danfoss A/S © 06/2015 All rights reserved.
MI70I102
