Automationdirect.com Stellar SR44, User Manual

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Chapter 2: Electrical Installation
2.4 – Motor Control Circuits
2.4.1 – Bypass Control
A separate bypass contactor may be connected in parallel with an SR44 Soft Starter. The bypass
contactor allows a solid connection of the motor to the Main Supply, which will eliminate the
heating effect associated with Soft Starter thyristor losses. Soft-Starting and Soft-Stopping remain
active as normal when the wiring is configured as in Figure 2.4.1.
At the completion of the starting ramp a bypass contactor is closed around the main power supply
connections of the Soft Starter to remove the thyristors from the circuit. The contactor is controlled
by a programmable relay set as ’Bypass Relay’, which is the default for relay K2. This configuration
ensures that bypassing only occurs after the Soft Starter has completed the start (P8/B3=1), and the
motor terminal voltage is at supply voltage.
The default configuration will detect the use of a bypass contactor when using this circuit
arrangement, since "Auto bypass" is set as standard. You can also pre-set the protection mode to
either "START+BYPASS" or "PHASE LOSS ONLY" for motor bypassing configurations.
Figure 2.4.1: Power and Contactor Control Circuits for Motor Bypassing
When using a bypass contactor, the “Auto Bypass” Auto Feature should be ON (P18/B2; P86/B2). Using
a bypass contactor with Auto Bypass in the OFF state can cause thyristor faults.
An external user-supplied current transformer is required if any of the current or power related trip or
monitoring features are needed in bypass mode. (Parameters: 8/B2, 9/B1/B2, 20, 21, 22, 23, 26, 28,
30, 32, 33, 34, 36, 39, 51/B1/B2/B3/B4, 87, 89, 91, 93, 112/B0/B1/B2/B3/B6, 121/B4)
CT must be installed in the L3-T3 power phase OUTSIDE of the bypass circuit. See control section 2.5.2.
L N
Control Supply
115VAC or 230VAC – set voltage switch acordingly
E-STOP STOP
START
C2
C2
C1
X1 X2
C2
SR44 Control Supply Card
SR44 Electronic Control Card
Control
Voltage
Switch
115V/230V
C3
11
21
S1
14
24
S0
J3 To Current
Transformer
(optional)
K1
K2
I/p1
Set the Control Voltage Switch to the proper
control voltage setting before applying
voltage to the control circuit.
Mains
Supply
L1
L2
L3
Feeder cables
Isolation and Protection
Switch-gear
(provided by the customer)
Electrical
Ground
1
L1
2
T1
4
T2
6
T3
3
L2
5
L3
Induction
Motor
SR44
Bypass
Contactor
C3
C1
– Circuit Contactor
CT* –
Current Transformer (optional)
(must be installed in L3 phase)
(see control wiring info section 2.5.2)
OL – if not using CT
*CT Specifications (User Supplied)
1000/1 ratio; class 1 (1% accuracy)
Crompton M93R-1000/1,
Ohio Semitronics CTY-1000C-1,
Mitchell Instrument Co. 2547ASH-1000-1
or equivalent
SR44 Series Soft Starter User Manual
1st Ed, Rev B 07/31/2019
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