Crompton Controls M20 - Manual (Page 54)

1 Emotron AB 01-4481-01r1
Emotron M20 Shaft Power Monitor
Special functions (windows 35, 36
and 65) ”Reverse function”
This instruction is valid for Emotron M20, 01-25
51-01,
(from software version R3B).
The reverse function can be used to reverse (drive back-
wards) motor driven equipment such as e.g. a screw con-
veyor when a “jam” occurs. With this function the M20 can
be used to prevent expensive stops and breakdowns in
machinery for example; blocked chip feeder, jammed lime
feeder, blocked slurry pump or in other similar applications.
In the case of a screw conveyor or chip feeder, for instance,
when an overload or jam-up occurs, the Emotron M20
reverses the “conveyor” automatically. Normally this would
clear the jammed material and then enable the conveyor to
feed forward again.
Should one reverse cycle (drive backwards) not be enough to
release the material, the monitor will repeat this operation
up to a maximum of five start attempts. If the conveyor is
still jammed, the monitor stops the conveyor motor/
machine from any further operation and an alarm is given.
The conveyor would then have to be cleaned manually and
the monitor reset. The number of start attempts and the
reverse time can be set. If set number of start attempts is
enough to release the material the conveyor will feed forward
again, and reset the previous number of start attempts, but
only after the conveyor has fed forward for least 60 seconds
and if the selected start and response delay time has elapsed.
Wiring, Programming and Operation
For wiring, programming and operation see the correspond-
ing sections in the Installation manual for the M20. See also
under 9 Advanced Features and the headline Special func-
tions (windows 35, 36 and 65) as well as the special connec-
tion example in Figure 1 (this example can also be found at
the end of this instruction).
The output relay contacts, terminals 6, 7 and 8 connect to
the motor control circuit and to the respective contactor; i.e.
terminal 7 to K1 (R1) = Forward and terminal 8 to K2 (R2)
= Reverse (see fig. 1). Terminal 5 can be used for external
reset and has the same function as the reset button on the
front of the monitor.
Analogue output
In this Reverse function application the analogue output will
go to its maximum 20 mA when the number of allowed start
attempts has elapsed. The output signal can for example be
used as an input to PLC´s or similar equipment to handle
the alarm etc. If a potential free relay contact is required, the
following external relay is recommended as an accessory:
• Schrack / Tyco RT174012 12 VDC (10A 250VAC)
• Camden DIN-rail relay socket C 250 3P
Set the monitor as follows
(First perform settings according to the applicable parts of
the M20 Monitor installation manual):
1. In this application it is unusual that both overload and
underload monitoring is used and unless the underload
is required in some other function window 5 should be
set to monitor overload only (
-
).
2. Start the motor/machine and let it run at normal load
until the start delay has elapsed - the machine load is
shown in the monitor display.
3. Press the “Auto set” button for 3 seconds.
4. Adjust start attempts (window 36), start delay (window
31), response delay (window 32, alt 34 at min), reverse
time (window 35) etc. as required.
It is also possible to set the alarm level manually, see the
manual and chapter 4 Getting Started.
Operation – Alarm
When an overload occurs for longer than the selected
response delay (window 32), the following sequence takes
place if there are still some start attempts available:
1. Motor is switched-off and stands for 3 seconds.
2. Motor is reversed during chosen reversal time, window
35 (If the monitor senses an overload during reversal the
motor will stop).
3. Once again, the motor is switched-off and stands for 3
seconds.
4. Motor re-starts automatically in forward mode.
For a prolonged jam-up, the monitor will carry out the max-
imum of reverse cycles set in window 36. If this does not
clear the blockage, the motor is switched-off and the ana-
logue output will go to its maximum 20 mA “permanent”
stop and alarm. When this occurs, the conveyor/machine
must be cleaned manually and the monitor reset, either by
CAUTION: Study thoroughly section 2 Safety in the Emotron
M20 Instruction manual before installing and using the
monitor. Please note that the machine starts and stops
automatically during set-up and running when the reverse
function is used!
NOTE:
To implement the above Reverse function, it will be
necessary for a forward and reversing motor starter
(contactors) to be installed.
Relay R1 and R2 (K1 and K2) must not be energized/on at
the same time as this will generate a short circuit.
Therefore it is important that window 65 = “2” before the
relays are connected to the contactors and it is also
recommended that the Forward and Reverse contactors
are also electrically interlocked.
Please note that an external alarm relay connected to the
analogue output must be specified as the above relay coil
voltage, resistance, power etc to ensure correct operation
and life time.