Compressor
Start
Phase monitoring
Phase sequence module logic
21
sYsteM design RecoMMendations
phase sequence and reverse
rotation protection
current value found in the data sheets;
the MMT value appears as "A.Max" on
the compressor nameplate.
Further requirements for the external
overload protector are:
•
overcurrent
protection:
the
protector must trip within 2 minutes
at 110% of the MMT current.
•
locked rotor protection:
the
protector must trip within 10 seconds
upon starting at a locked rotor
current.
•
single-phasing protection:
the
protector must trip when one of the
three phases fails.
cycle rate limit
The system must be designed in a
way that guarantees a minimum
compressor run time of 2 minutes,
so as to provide for sufficient motor
cooling after start-up and proper oil
return. Oil return may vary since it
depends upon system design.
There must be no more than 12 starts
per hour (6 when a resistor soft-start
accessory is present); exceeding these
limits reduces the service life of the
compressor. If necessary, place an anti-
short-cycle timer in the control circuit,
connected as shown in the wiring
diagram (p. 14-15). A three-minute
(180-sec) setting is recommended.
Use a phase meter to establish the
phase orders and connect line phases
L1, L2, and L3 to terminals T1, T2, and
T3, respectively. The compressor
will only operate properly in a single
direction, and the motor is wound so
that if the connections are correct, the
rotation will also be correct.
compressor models sM / sZ 084
to 185
incorporate an internal
reverse vent valve which will react
in the presence of reverse rotation
and allows refrigerant to circulate
through a by-pass from suction to
discharge. Although reverse rotation
is not destructive, even over long
periods of time up to several days
it should be corrected as soon as
possible. Reverse rotation will be
obvious to the user as soon as power
is turned on; the compressor will not
build up any pressure, the sound
level will be abnormally high and
power consumption will be minimal. If
reverse rotation symptoms occur, shut
the compressor down and connect
the phases to their proper terminals.
If reverse rotation is not halted, the
compressor will cycle off on its internal
motor protection.
compressor models sY / sZ 240 to
380
are delivered with an electronic
module which provides protection
against phase reversal and phase loss
at start-up. Use the recommended
wiring diagrams from page 15. The
circuit should be thoroughly checked
in order to determine the cause of the
phase problem before re-energizing
the control circuit.
The phase sequencing and phase
loss monitoring functions are active
during a 5 sec. window 1 sec. after
compressor start-up (power on L1-L2-
L3). Should one of these parameters
be incorrect, the relay would lock out
(contact M1-M2 open). The lockout
may be cancelled by resetting the
power mains (disconnect L-N) for
approximately 5 sec.
Summary of Contents for Performer SM Series
Page 39: ......
