York YCAS Installation Operation & Maintenance Download

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138

YORK INTERNATIONAL

FORM 201.19-NM6 (804)

1.8 TRANSFORMERS

3 Transformers (2T, 3T, and 4T) are located in the
Con trol Panel. These transformers convert the 115VAC
Control Power Input to 24VAC to operate the mi cro pro -
ces sor circuitry.

1T: Supplies 24V to I/O Expansion Board # 2

2T: This 75VA transformer supplies 24VAC to

the microprocessor power supply board.

3T: Supplies the I/O Expansion Board # 1

voltage for slide valve control.

4T:

Supplies 24VAC power to the 2ACE Motor
Protector Modules.

1.9 MOTOR PROTECTOR MODULES

A Motor Protector Module for each compressor is lo-
cat ed in the Control Panel. These modules supply mo tor
over-temperature protection, 3-phase current pro tec tion,
phase imbalance, phase rotation, and a pro gram ming and
troubleshooting 7 segment display.

The motor over-temperature protection is supplied by
3 temperature sensors imbedded in the motor wind ings
120 degrees apart. The module monitors these sensors
allowing it to sense a hot winding and shut down the
compressor if motor cooling is inadequate.

The on-board C.T.s provide 3 phase cur rent pro-
tec tion which look at 3 of the 6 motor legs and send
an analog signal proportional to average motor cur rent
to I/O Expansion board and on to the mi cro pro ces sor
board for microprocessor low/high current pro tec tion
and current display. This allows the micro to monitor
cur rent and shut a system down if low or high motor cur-
rent is sensed. This is a non-adjustable pro tec tion cir cuit
electronically sized to a system's motor spec i fi ca tions.

Internally, the (3) on-board 3C.T.s and internal circuitry
allow the Motor Protector Module to protect against high
motor current as programmed on the Motor Pro tec tor dip
switches. These switches are set at the fac to ry according
to motor specifi cations.

The module also provides phase rotation protection to as-
sure the screw compressor does not rotate back wards

A single phase protection circuit located in the module
monitors for a phase imbalance. If current im bal ance
exceeds 17% of the average motor current in one of the
phases, the Motor Protector will recognize it and shut
the system down.

Whenever the Motor Protector Module senses a fault,
internal contacts M1 - M2 will open and shut the sys-
tem down. These contacts are wired in series with the
compressor motor contactor. When the contacts open,
the micro will attempt to start the system 2 more times.
Since the motor contactor signal path from the Relay
Output Board to the motor contactor is broken by the
Motor Protector Module contacts, it will lock the system
out after 3 faults. The Motor Protector Module must then
be reset by removing 115VAC power from the Control
Panel. After the Motor Protector is reset, the individual
sys tem SYS switch (S2-S5) must be switched OFF and
then ON to reset the microprocessor to al low restart of
the system.

Anytime the module faults, a thor ough
in ves ti ga tion  of  the  problem  should  be
per formed  be fore  at tempt ing  to  re turn
the  system  to  op er a tion.  Fail ure  to
per form  this  in ves ti ga tion  could  lead
to motor or com pres sor failure. Ad di -
tion al de tails on the Mo tor Pro tec tor
Module can be found on page 16.

Always review the data in the HIS-
TORY BUFFER when faults occur.
Since the micro attempts to restart 2
more times after the fi rst fault, which
opens the M1 and M2 contacts, the last
2 faults will show Low CURR/MP/HP,
but will have no value for trouble-
shooting. The information contained
in HISTORY BUFFER #3 will be use-
ful on troubleshooting the cause of the
Mo tor Pro tec tor fault.

Micro Panel Contents