Automationdirect.com Stellar SR44, User Manual

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2.4.2 – Multiple Motor Starting & Stopping
The SR44 is capable of starting parallel-connected motors simultaneously, provided each motor
has similar characteristics and load. For such configurations the unit rating should be at least the
sum of the current ratings of all the motors.
Alternatively, the SR44 can start and stop motors sequentially using bypass contactors under the
control of the programmable relay set as a ’Top of Ramp’ relay. The dual setting feature allows for
the control of motors with different start-up requirements.
2.4.3 – External Motor Protection Relay
The rating for a motor protection relay should be for Direct-on-Line (DOL) starting, and if it is an
electronic relay, then the user should confirm it’s suitability for use with a soft-starter. If the motor
load is high-inertia (extended start time), then a longer trip time may be required.
2.4.4 – Motor Reversing
The diagram in figure 2.4.6 shows a typical motor reversing circuit using two contactors, C1 and
C2, to interchange two phases of the 3-phase power supply connections.
For this application the soft stop must be set to zero.
We also recommend the following:
• A period of 150 - 350 ms elapses between the FORWARD and REVERSE commands.
• If the reversing rate is high, the SR44 current rating may need to be increased compared to the
operational current of the motor. Refer to sections 2.10.3 & 2.10.4, and also the Overcurrent trip
curves shown in section 2.10.5.
• The current limit and the overload must be set with more consideration to the “reverse” function
rather than the “start”, as the motor will initially be “plug braked” then be stationary for a moment
and finally undergo a normal soft start.
Chapter 2: Electrical Installation
SR44 Series Soft Starter User Manual
1st Ed, Rev B 07/31/2019