Specifications

2.8.3 PM/EC+ Motor Control
The Danfoss EC+ concept provides the possibitily for using
high efficient PM motors in IEC standard enclosure types
operated by Danfoss frequency converters.
The commissioning procedure is comparable to the
existing one for asynchronous (induction) motors by
utilising the Danfoss VVC
plus
PM control strategy.
Customer advantages:
•
Free choice of motor technology (permanent
magnet or induction motor)
•
Installation and operation as known for induction
motors
•
Manufacturer independent when choosing system
components (e.g. motors)
•
Best system efficiency by choosing best
components
•
Possible retrofit of existing installations
•
Power range: 1.1–22 kW
Current limitations:
•
Currently only supported up to 22 kW
•
Currently limited to non salient type PM motors
•
LC filters not supported together with PM motors
•
Over Voltage Control algorithm is not supported
with PM motors
•
Kinetic back-up algorithm is not supported with
PM motors
•
AMA algorithm is not supported with PM motors
•
No missing motorphase detection
•
No stall detection
•
No ETR function
2.8.4
Sizing of Frequency Converter and
PM motor
The low motor inductances of PM motors can cause
current ripples in the frequency converter.
To select the right frequency converter for a given PM
motor, ensure that:
•
The frequency converter can deliver the required
power and current in all operating conditions.
•
The power rating of the frequency converter is
equal to or higher than the power rating of the
motor.
•
Size the frequency converter for a constant 100%
operating load with sufficient safety margin.
The current (A) and the typical power rating (kW) for a PM
motor can be found in chapter 9.1 Mains Supply Tables for
different voltages.
Sizing examples for nominal power rating
Example 1
•
PM motor size: 1.5 kW / 2.9 A
•
Mains: 3 x 400 V
Freque
ncy
Convert
er
Typical
[kW]
Typical
[hp] at
460V
Continu
ous [A]
(3x380-
440 V)
Intermi
tted [A]
(3x380-
440V)
Continu
ous [A]
(3x441-
480 V)
Intermi
tted [A]
(3x441-
480V)
P1K1 1.1 1.5 3.0 3.3 2.7 3.0
P1K5 1.5 2.0 4.1 4.5 3.4 3.7
Table 2.10 Sizing Data for 1.1 and 1.5 kW Frequency Converters
The current rating of the PM motor (2.9 A) matches the
current rating of both the 1.1 kW frequency converter (3 A
@ 400 V) and the 1.5 kW frequency converter (4.1 A @ 400
V). However, since the power rating of the motor is 1.5 kW,
the 1.5 kW frequency converter is the correct choice.
Motor Frequency Converter 1.5 kW
Power 1.5 kW 1.5 kW
Current 2.9 A 4.1 A @ 400V
Table 2.11 Correctly Sized Frequency Converter
Example 2
•
PM motor size: 5.5 kW / 12.5 A
•
Mains: 3 x 400 V
Freque
ncy
Convert
er
Typical
[kW]
Typical
[hp] at
460V
Continu
ous [A]
(3x380-
440 V)
Intermi
tted [A]
(3x380-
440V)
Continu
ous [A]
(3x441-
480 V)
Intermi
tted [A]
(3x441-
480V)
P4K0 4.0 5.0 10.0 11.0 8.2 9.0
P5K5 5.5 7.5 13.0 14.3 11.0 12.1
Table 2.12 Sizing Data for 4.0 and 5.5 kW Frequency Converters
The current rating of the PM motor (12.5 A) matches the
current rating of the 5.5 kW frequency converter (13 A @
400 V), not the current rating of the 4.0 kW frequency
converter (10 A @ 400 V). Since the power rating of the
motor is 5.5 kW, the 5.5 kW frequency converter is the
correct choice.
Motor Frequency Converter 5.5 kW
Power 5.5 kW 5.5 kW
Current 12.5 A 13 A @ 400V
Table 2.13 Correctly Sized Frequency Converter
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Design Guide
34 Danfoss A/S © Rev. 06/2014 All rights reserved. MG11BC02
22