Local Isolator No; Contactor Status; Dielectric Strength Testing - GE Multilin MM3 Motor Manager 3 Instruction Manual

INPUTS AND OUTPUTS
2.3.16 Local Isolator
NO
2.3.17 Contactor
Status
2.3.18 Dielectric
Strength
Testing
CAUTION
2–6
The local isolator NO auxiliary contacts are used to prevent motor starts in the event of the
local isolator being in the "open" position. To prevent starts, the MM3 Motor Manager 3
produces a trip when the local isolator input is open. A local isolator trip is automatically
reset when the local isolator is reclosed.
The local isolator input can be enabled or disabled as required. The factory default is
disabled.
The MM3 Motor Manager 3 must know the state of the contactor at all times in order to
detect discrepancies in contactor close/open commands and also to display the state of
the contactor. There are two contactor status inputs on the MM3 Motor Manager 3, one for
contactor A, the other for contactor B.
Auxiliary contacts mechanically linked to the contactor itself are used to feed back to the
contactor status inputs. No status change following a start command indicates an open
contactor control circuit and no status change following stop command indicates a
welded contactor. Appropriate messages and alarms are displayed for these conditions
and the status can be read via the serial port.
If the motor contactor is externally energized, the MM3 Motor Manager 3 will seal in the
output relay and display an "EXTERNAL START" message. If the motor contactor is
externally de-energized, the MM3 Motor Manager 3 will drop out the output relay and
display an "EXTERNAL STOP" message.
It may be required to test a complete MCC with MM3 Motor Manager 3s installed for
dielectric strength. This is also known as "flash" or "hipot" testing. The MM3 Motor Manager
3 is rated for 1800 V AC for 1 minute or 2200 V AC for 1 second isolation between switch
inputs, relay outputs, VT voltage input, supply voltage inputs and ground terminals 21 and
48.
When performing dielectric tests, the connection to the surge ground terminal (22) must be
removed. A filter network is used on the AC input to filter out RF and EMI noise. The filter
capacitors and transient absorbers could be damaged by the high voltages relative to
surge ground on the AC input.
Under no circumstances should any inputs other than switches, relays, supply voltage,
and VT input be dielectric tested.
CHAPTER 2: INSTALLATION
MM3 MOTOR MANAGER 3 – INSTRUCTION MANUAL