Figure 4-11 Preferred Chain Connection For Multiple Motors; Figure 4-12 Alternative Connection For Multiple Motors - Emerson unidrive sp User Manual

Safety Mechanical
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Information information Installation
For normal operation with AC supplies up to 500Vac and a standard
motor with a good quality insulation system, there is no need for any
special precautions. In case of doubt the motor supplier should be
consulted.
Special precautions are recommended under the following conditions,
but only if the motor cable length exceeds 10m:
• AC supply voltage exceeds 500V
• Operation of 400V drive with continuous or very frequent sustained
braking
• Multiple motors connected to a single drive
For multiple motors, the precautions given in section 4.6.3 Multiple
motors should be followed.
For the other cases listed, it is recommended that an inverter-rated
motor be used. This has a reinforced insulation system intended by the
manufacturer for repetitive fast-rising pulsed voltage operation.
Users of 575V NEMA rated motors should note that the specification for
inverter-rated motors given in NEMA MG1 section 31 is sufficient for
motoring operation but not where the motor spends significant periods
braking. In that case an insulation peak voltage rating of 2.2kV is
recommended.
If it is not practical to use an inverter-rated motor, an output choke
(inductor) should be used. The recommended type is a simple iron-cored
component with a reactance of about 2%. The exact value is not critical.
This operates in conjunction with the capacitance of the motor cable to
increase the rise-time of the motor terminal voltage and prevent
excessive electrical stress.
4.6.3 Multiple motors
Open-loop only
If the drive is to control more than one motor, one of the fixed V/F modes
should be selected (Pr 5.14 = Fd or SrE). Make the motor connections
as shown in Figure 4-11 and Figure 4-12. The maximum cable lengths in
Table 4-7 apply to the sum of the total cable lengths from the drive to
each motor.
It is recommended that each motor is connected through a protection relay
since the drive cannot protect each motor individually. For A connection, a
sinusoidal filter or an output inductor must be connected as shown in
Figure 4-12, even when the cable lengths are less than the maximum
permissible. For details of inductor sizes refer to the supplier of the drive.

Figure 4-11 Preferred chain connection for multiple motors

Chain connection (preferred)
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Figure 4-12 Alternative connection for multiple motors

A / Δ motor operation
4.6.4
The voltage rating for A and Δ connections of the motor should always
be checked before attempting to run the motor.
The default setting of the motor rated voltage parameter is the same as
the drive rated voltage, i.e.
400V drive 400V rated voltage
690V drive 690V rated voltage
A typical 3 phase motor would be connected in A for 400V operation or Δ
for 200V operation, however, variations on this are common e.g.
A 690V Δ 400V
Incorrect connection of the windings will cause severe under or over
fluxing of the motor, leading to a very poor output torque or motor
saturation and overheating respectively.
4.6.5 Output contactor
If the cable between the drive and the motor is to be
interrupted by a contactor or circuit breaker, ensure that the
drive is disabled before the contactor or circuit breaker is
opened or closed. Severe arcing may occur if this circuit is
WARNING interrupted with the motor running at high current and low
speed.
A contactor is sometimes required to be installed between the drive and
motor for safety purposes.
The recommended motor contactor is the AC3 type.
Switching of an output contactor should only occur when the output of
the drive is disabled.
Opening or closing of the contactor with the drive enabled will lead to:
1. OI.AC trips (which cannot be reset for 10 seconds)
2. High levels of radio frequency noise emission
3. Increased contactor wear and tear
The Drive Enable terminal (T31) when opened provides a SECURE
DISABLE function. This can in many cases replace output contactors.
For further information see section 4.13 SAFE TORQUE OFF (SECURE
DISABLE) on page 69.
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Motor protection
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Star connection
Inductor
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