Current Measurement On All Three Motor Phases; Galvanic Isolation Of Control Terminals; Custom Application Functions; Automatic Motor Adaptation - Danfoss VLT AQUA Drive FC 202 Design Manual

Product Overview
frequency converter is designed to comply with the EMC
product standard for drives IEC 61800-3 as well as the
European standard EN 55011. To comply with the emission
levels in EN 55011, the motor cable must be shielded and
properly terminated. For more information regarding EMC
performance, see chapter 3.2.2 EMC Test Results.
2.5.19 Current Measurement on All Three
Motor Phases
Output current to the motor is continuously measured on
all 3 phases to protect both the frequency converter and
motor against short-circuits, ground faults, and phase loss.
Output ground faults are instantly detected. If a motor
phase is lost, the frequency converter stops immediately
and reports which phase is missing.
2.5.20 Galvanic Isolation of Control
Terminals
All control terminals and output relay terminals are galvan-
ically isolated from mains power. This means the controller
circuitry is completely protected from the input current.
The output relay terminals require their own grounding.
This isolation meets the stringent protective extra-low
voltage (PELV) requirements for isolation.
The components that make up the galvanic isolation are:
•
Power supply, including signal isolation.
•
Gate drive for the IGBTs, trigger transformers, and
optocouplers.
•
The output current Hall effect transducers.

2.6 Custom Application Functions

Custom application features are the most common
features programmed in the frequency converter for
enhanced system performance. They require minimum
programming or set-up. Understanding that these features
are available can optimise the system design and possibly
avoid introducing redundant components or functionality.
See the programming guide for instructions on activating
these functions.

2.6.1 Automatic Motor Adaptation

Automatic motor adaptation (AMA) is an automated test
procedure used to measure the electrical characteristics of
the motor. AMA provides an accurate electronic model of
the motor. It allows the frequency converter to calculate
optimal performance and efficiency with the motor.
Running the AMA procedure also maximises the automatic
energy optimisation feature of the frequency converter.
AMA is performed without the motor rotating and without
uncoupling the load from the motor.
MG20N602
Design Guide

2.6.2 Motor Thermal Protection

Motor thermal protection can be provided in 3 ways:
•
•
•
ETR calculates motor temperature by measuring current,
frequency, and operating time. The frequency converter
displays the thermal load on the motor in percentage and
can issue a warning at a programmable overload setpoint.
Programmable options at the overload allow the frequency
converter to stop the motor, reduce output, or ignore the
condition. Even at low speeds, the frequency converter
meets I2t Class 20 electronic motor overload standards.
2000
1000
600
500
400
300
200
100
60
50
40
30
20
10
Illustration 2.18 ETR Characteristics
The X-axis in Illustration 2.18 shows the ratio between I
and I
motor
before the ETR cuts off and trips the frequency converter.
The curves show the characteristic nominal speed, at twice
the nominal speed and at 0.2 x the nominal speed.
At lower speed, the ETR cuts off at lower heat due to less
cooling of the motor. In that way, the motor is protected
from being overheated even at low speed. The ETR feature
calculates the motor temperature based on actual current
and speed. The calculated temperature is visible as a read-
out parameter in 16-18 Motor Thermal.
Danfoss A/S © 09/2014 All rights reserved.
Via direct temperature sensing via one of the
following:
- PTC sensor in the motor windings and
connected on a standard AI or DI.
- PT100 or PT1000 in the motor windings
and motor bearings, connected on VLT
Sensor Input Card MCB 114.
-
PTC thermistor input on VLT
Tthermistor Card MCB 112 (ATEX
approved).
Mechanical thermal switch (Klixon type) on a DI.
Via the built-in electronic thermal relay (ETR) for
asynchronous motors.
t [s]
1.0 1.2 1.4 1.6 1.8 2.0
nominal. The Y-axis shows the time in seconds
2
®
®
PTC
f OUT = 1 x f M,N (par. 1-23)
f OUT = 2 x f M,N
f OUT = 0. 2 x f M,N
I
M
I (par. 1-24)
MN
motor
29
2