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Product Description
The software is stored in non-volatile memory (EPROM)
to eliminate chiller failure due to AC power failure. The
Programmed Setpoint is stored in lithium battery backed
memory.
Motor Current Protection
The microprocessor motor protection provides high cur-
rent protection to assure that the motor is not damaged
due to voltage, excess refrigerant, or other problems
that could cause excessive motor current. This is ac-
complished by sending 3-phase current signals propor-
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.
16
Motor Protection Module
The mechanical motor protector is a Texas Instruments
2ACE Three Phase Protection Module (Fig. 36, page
102) 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:
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 protector
contacts wired in series with the motor contacts opens
and the motor contactor de-energizes allowing the mo-
tor 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 re-
set device. After the first start the modules' contacts
will be open preventing the motor contactors from en-
ergizing. Power must be removed and reapplied to re-
set the module.
YORK INTERNATIONAL
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