Derating - Danfoss VLT AQUA Drive FC 202 Design Manual

Mechanical Installation Con...
Frame
D1h
D2h
D3h
D4h
D5h
D6h
D7h
D8h
Table 9.2 D1h–D8h Airflow Rate
Frame
E1h
E2h
E3h
E4h
Table 9.3 E1h–E4h Airflow Rate
9 9

9.6 Derating

Derating is a method used to reduce output current to
avoid tripping the drive when high temperatures are
reached within the enclosure. If certain extreme operating
conditions are expected, a higher-powered drive can be
selected to eliminate the need for derating. This is called
manual derating. Otherwise, the drive automatically
derates the output current to eliminate the excessive heat
generated by extreme conditions.
Manual derating
When the following conditions are present, Danfoss
recommends selecting a drive 1 power size higher (for
example P710 instead of P630):
•
Low-speed – continuous operation at low RPM in
constant torque applications.
•
Low air pressure – operating at altitudes above
1000 m (3281 ft).
•
High ambient temperature – operating at
ambient temperatures of 10 °C (50 °F).
•
High switching frequency.
•
Long motor cables.
•
Cables with a large cross-section.
152
VLT
Door fan/top fan Heat sink fan
3 3
[m /hr (cfm)] [m
102 (60) 420 (250)
204 (120) 840 (500)
102 (60) 420 (250)
204 (120) 840 (500)
102 (60) 420 (250)
102 (60) 420 (250)
204 (120) 840 (500)
204 (120) 840 (500)
Door fan/top fan Heat sink fan
[m 3 /hr (cfm)] [m 3
510 (300) 994 (585)
552 (325) 1053–1206 (620–710)
595 (350) 994 (585)
629 (370) 1053–1206 (620–710)
Danfoss A/S © 01/2018 All rights reserved.
®
AQUA Drive FC 202
Automatic derating
If the following operating conditions are found, the drive
/hr (cfm)]
automatically changes switching frequency or switching
pattern (PWM to SFAVM) to reduce excessive heat within
the enclosure:
•
•
•
NOTICE!
Automatic derating is different when
parameter 14-55 Output Filter is set to [2] Sine-Wave Filter
Fixed.
/hr (cfm)]
9.6.1 Derating for Low-Speed Operation
When a motor is connected to a drive, it is necessary to
check that the cooling of the motor is adequate. The level
of cooling required depends on the following:
•
•
•
Constant torque applications
A problem can occur at low RPM values in constant torque
applications. In a constant torque application, a motor can
overheat at low speeds because less cooling air is being
provided by the fan within the motor.
If the motor is run continuously at an RPM value lower
than half of the rated value, the motor must be supplied
with extra air cooling. If extra air cooling cannot be
provided, a motor designed for low RPM/constant torque
applications can be used instead.
Variable (quadratic) torque applications
Extra cooling or derating of the motor is not required in
variable torque applications where the torque is propor-
tional to the square of the speed, and the power is
proportional to the cube of the speed. Centrifugal pumps
and fans are common variable torque applications.
High temperature on the control card or heat
sink.
High motor load or low motor speed.
High DC-link voltage.
Load on the motor.
Operating speed.
Length of operating time.
MG22B222