SSD 605C, Product Manual

Page: 209 / 236

Application Notes
13-3
605C Frequency Inverter
Using Multiple Motors on a Single Drive
A single large Inverter can be used to supply several smaller motors provided that each
individual motor has overload protection.
Note: Conventional V/F control strategy must be
enabled for use with parallel motors. (Sensorless
vector control strategy cannot be used). See the
VECTOR ENABLE parameter under VECTOR SET-
UP menu at level 2.
The Inverter must be rated to supply the total motor
current . It is not sufficient to simply sum the power
ratings of the motors, since the Inverter has also to
supply the magnetising current for each motor.
Note that the overload device will not prevent the
motor overheating due to inadequate cooling at low
speed. Force vented motors may be required; consult
your motor supplier.
WARNING!
All motors should be connected to the
Inverter output before the
START
command is
given.
Caution
Restrict the total cable length on multiple motor installations as follows:
50 metres with no output choke fitted,
300 metres with choke.
Dynamic Braking
During deceleration, or with
an overhauling load, the
motor acts as a generator.
Energy flows back from the
motor into the dc link
capacitors within the drive.
This causes the dc link
voltage to rise. If the dc link
voltage exceeds 810V for
the 400V build (or 890V for
the 500V build) then the
drive will trip to protect the
capacitors and the Inverter
power devices. The amount
of energy that can be
absorbed in the capacitors is
relatively small; typically
more than 20% braking
torque will cause the drive to trip on overvoltage. Dynamic braking increases the braking
capability of the drive by dissipating the excess energy in a high power resistor connected
across the dc link, see above. Refer to Figure 3-9 for connection details.
M1 M2
605C
OL1 OL2
M1/U M2/V M3/W
Figure 13-1 Single Inverter supplying
multiple Motors
GATE
DRIVE
CIRCUIT
+
EXTERNAL
RESISTOR
NETWORK
Figure 13-2 Dynamic Braking Circuit