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tional to motor current from the Motor Protector mod-
ule to the Power Supply Board where the signals are
conditioned and routed to the I/O Expansion Board to
be multiplexed and sent to the Microprocessor Board.
If the motor current exceeds the 115% FLA trip point
after 3 seconds of operation on either Wye-Delta or
ACL starters, the micro will shut the system down and
lock it out after one fault. A manual reset of the re-
spective system switch is required to clear the fault
and restart the system. A thorough check of the mo-
tor, wiring, and refrigerant system should be done be-
fore restarting a system that has faulted on high motor
current.
The micro also provides low motor current protection
when it senses a motor current less than 10% FLA. The
micro will shut the system down whenever low motor
current is sensed and will lock out a system if three
faults occur in 90 minutes. Low motor current protec-
tion is activated 4 seconds after start on both Wye-Delta
and ACL starters to assure the motor starts, the system
doesn't run without refrigerant, the motor protector is
not tripped, and the mechanical high pressure cut-out
is not tripped. Once the system is locked out on Low
Motor Current, it must be manually reset with the sys-
tem switch. See also Motor Protection Module section
below.
The micro senses low motor current whenever a HPCO
or Motor Protector contact opens. This occurs because
the MP and HPCO contacts are in series with the motor
contactor. Whenever either of these devices are open,
the contactor de-energizes and the motor shuts down.
Since the micro is sending a run signal to the contactor,
it senses the low motor current below 10% FLA and
shuts the system down.
Motor Protection Module
The mechanical motor protector is a Texas Instruments
2ACE Three-Phase Protection Module (Fig. 62, page
133) thermal and current motor overload protection. This
module protects against phase to phase current imbal-
ance, over current, under current, and phase rotation.
The module, mounted in the power panel, utilizes a 7
segment display which provides operating status and
fault diagnostic information. The 7 segment display will
display either a stationary or a flashing alphanumeric
value which can be decoded by the operator. A list of
the codes follows:
16
HAXXX
Normal motor OFF display. Sequentially
sweeps through the motor protection dip
switch setting.
0
Normal - no fault detected (Running)
Flashing "0"
Motor off or unloaded < 5A (Running)
AC current level.
1
High current fault.
Loaded phase to phase current
2
imbalance > 17%.
Unloaded phase to phase current
3
imbalance > 25%.
4
Improper incoming phase rotation.
High motor temperature. Trip point =
5
13kW, reset = 3.25kW.
6
Communication error.
7
Unload imbalance ( > 50%)
8
Phase Loss (> 60%)
E
Out of range of RLA calibration.
Other symbols Defective module or supply voltage.
Working voltage 18 - 30 VAC, 224 VAC nominal.
Low voltage trip = 15 VAC.
Whenever a motor protector trips, the motor protec-
tor contacts wired in series with the motor contacts
opens and the motor contactor de-energizes allowing
the motor to stop. The micro senses the low motor
current and shuts the system down. The micro will try
two more starts before locking the system out. The
system locks out because the motor protector is a
manual reset device. After the first start the modules'
contacts will be open preventing the motor contactors
from energizing. Power must be removed and reapplied
to reset the module.
Current Overload
The 2ACE module design uses one integral current
transformer per phase to provide protection against
rapid current overload conditions. The module responds
to changes in current and must be calibrated using DIP
switches located on the module. Integral trip curves al-
low for in-rush currents during Wye-Delta, part wind,
or ACL starts without nuisance tripping.
To check the factory setting of the 2ACE module cur-
rent overload trip value, obtain the RLA from the mo-
tor nameplate. The method used to calculate the trip
value will depend on the type of start (Across-The-Line
or Wye-Delta) and the number of wires in each phase
that are routed through the C.T.
YORK INTERNATIONAL
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