Motor Connection; Connecting Several Motors - Danfoss VLT Decentral Drive FCD 302 Operating Manual

Electrical Installation

4.7 Motor Connection

WARNING
INDUCED VOLTAGE
Induced voltage from output motor cables that run
together can charge equipment capacitors even with the
equipment turned off and locked out. Failure to run
output motor cables separately or to use shielded cables,
4 4
could result in death or serious injury.
NOTICE
MOTOR OVERLOAD PROTECTION
Protection against motor overload is not included in the
factory setting. If this function is needed, set
parameter 1-90 Motor Thermal Protection to either 1 of
the trip options or 1 of the warning options. Refer to the
®
VLT AutomationDrive FC 301/302 Programming Guide for
further information.
1. Connect the motor to terminals 96, 97, 98.
2. Connect ground to the PE-terminal.
3. Make sure that the shield of the motor cable is
properly grounded at both ends (motor and
frequency converter).
4. For correct dimensioning of cable cross-section,
see chapter 7.1 Electrical Data.
Number
96 97 98 Motor voltage 0–100% of mains voltage.
U V W 3 wires out of motor.
U1 V1 W1
6 wires out of motor.
W2 U2 V2
U1 V1 W1 6 wires out of motor, star connected.
Connect U2, V2, W2 separately (optional terminal
block).
PE – – Ground connection.
Table 4.1 Terminals 96, 97, 98
NOTICE
Do not install power factor correction capacitors
between the frequency converter and the motor.
Do not wire a starting or pole-changing device between
the frequency converter and the motor.
20
®
VLT Decentral Drive FCD 302

4.7.1 Connecting Several Motors

Parallel connection of motors
The frequency converter can control several parallel-
connected motors. The total current consumption of the
motors must not exceed the rated output current I
the frequency converter.
NOTICE
•
•
NOTICE
The electronic thermal relay (ETR) of the frequency
converter cannot be used as motor overload protection
for the individual motor in systems with parallel-
connected motors. Provide further motor overload
protection by thermistors in each motor or individual
thermal relays. Circuit breakers are not suitable as
protection.
Illustration 4.10 Parallel Connection of Motors
Problems can occur at start-up and at low RPM values,
when motor sizes differ widely. Motors of low rated motor
power have a relatively high ohmic resistance in the stator.
This high-resistance calls for a higher voltage at start and
at low RPM values.
To resolve such a problem:
•
•
Danfoss A/S © 11/2016 All rights reserved.
Installations with cables connected in a
common joint as in Illustration 4.10, is only
recommended for short cable lengths
(maximum 10 m (32.8 ft)).
When motors are connected in parallel,
parameter 1-29 Automatic Motor Adaptation
(AMA) cannot be used.
Reduce the load during start-up on the motor of
lowest rated motor power.
Configure parallel connections only between
motors of comparable rated motor power.
for
M,N
MG04F502