VMX
2
Series Digital Solid State Soft Starter User Manual
81 |
P a g e
Appendix 4 (cont.) External OL Relay Applications
Across-the-Line (Direct-on-Line) Bypass
A suggested control schematic is shown below for using the
VMX2
…-
BP Series
rated for Across-the-Line Bypass with an External Overload:
Figure APP4.2: VMX2 Wiring for Across-the-Line Bypass Operation with External Overload Relay
(Only the terminals necessary for this operation are shown)
In this example:
The Start / Run command (2-wire or 3-wire) energizes a control Relay
“CR”. If the selector Switch is in the “SS” (Soft Start) position, the
contact of CR closes the 24VDC control signal to TB1, terminals 1 and 3
of the
VMX2 Series,
which begins ramping. When At-Speed status is
reached, an internal Bypass Pilot Relay is used to close the Bypass
Contactor. While in this mode, the
VMX2 Series
CPU provides full
motor protection, even when the Bypass Contactor closes.
When the Selector Switch is placed in the
“A-T-L” (Across-the-Line)
position, a 2
nd
isolated contact of CR is used to close the circuit between
B1 and B2 of TB4 which are internally connected in parallel to the
Bypass Pilot Relay contact in the Bypass Contactor coil circuit. Since
the
VMX2 Series
electronics may be out of service, an External
Overload is added which only operates in this mode and protects the
motor by dropping out the connection between B1 and B2.
Caution
:
The circuit on TB-4, is at the same potential as the AC control
voltage, but should not be directly connected to it. PC board
damage may result.
(Included as standard on all
VMX2B-CD enclosed units.)
