VMX
2
Series Digital Solid State Soft Starter User Manual
79 |
P a g e
Appendix 4 - External Overload Relay Applications
Your
VMX2 Series
starter comes equipped with a very intelligent
internal electronic overload protection system, and does not need an
external Overload Relay (OLR). There are instances; however, where
external OLRs are needed or desired because of the application. These
fall into three categories: Higher Level Protection systems, Redundant
Backup applications, and Special Motor applications.
▪
Note:
If the Deceleration Function is activated (F024), additional
consideration must be put into determining how the starter is to
operate in the event of an Overload Trip. See Section 5.6.5 for
issues regarding this application.
HIGHER LEVEL PROTECTION SYSTEMS
Because of a desire for uniformity and/or operator familiarity in some
facilities, Motor Protection Relays or other coordinated OEM protection
systems may be used in lieu of the
VMX2 Series
protection (even
though most of the features are the same or better). In these instances
the
VMX2 Series
Overload protection can simply be turned off,
deferring protection to the external devices. Care should be taken;
however, to ensure that the external device is properly wired into the
starter control circuit to facilitate shutdown of the motor.
REDUNDANT BYPASS STARTER APPLICATIONS:
In some applications, it may be necessary to provide an independent
means of starting and protecting the motor should the
VMX2 Series
starter become inoperable. If this were the case, the
Bypass Contactor
could be used for Across-the-Line (A.T.L.) starting of the motor. The
VMX2
…BP
version with Integral Bypass Contactors is designed for that
possibility, as long as the starter is properly selected when ordered. To
do so, select the starter based upon the ATL (Across-the-Line) selection
chart so that the contactor is rated for ATL duty instead of the normal
Shunt Duty.
Under normal operations, the Bypass Contactor is controlled internally
by the
VMX2 Series
PC board and an internal pilot relay. For redundant
backup purposes; however, terminals B1 and B2 of TB4 are provided
for field connection of a dry contact closure in parallel to the pilot relay
contact, allowing control even if the electronics are out of service. AC
control power must still be applied to TB2 terminals A1 and A2, but no
other electronics or power supplies need to be functioning. It is in this
instance that an external OLR must be added to the motor power circuit
and wired into that coil control circuit. TB4 is located in different areas of
each frame size in the
VMX2 Series
. Refer to the following diagram for
the location on your unit.
