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5.2 Screw Compressor
Motor Protection
06T Screw compressors must be applied with
properly sized calibrated circuit breakers or
Furnas "958" series solid-state overload relays
to protect the motor against overcurrent fault
conditions. Approved selections are shown in
section 5.3 for the 06TR and 06TA compres-
sors. Use of motor protection devices other
than those shown in this Application Manual
must be approved by Carlyle Application
Engineering. The use of authorized overcurrent
protection is part of the basis of UL recogni-
tion. Selection of alternate overcurrent protec-
tion without Carlyle's approval will void warran-
ty. For proper overcurrent protection, the must
trip setting of the protection device must not
exceed the compressor Maximum Must Trip
Amps shown in the tables. The selected com-
pressor overcurrent device must trip in 2 to 6
seconds at the LRA value shown for the com-
pressor.
The circuit breakers and overload relays select-
ed by Carlyle are manually reset and have
been sized to protect the compressor against
running overcurrent, locked rotor, primary and
secondary single phasing. These devices also
offer the additional advantage of protecting the
compressor against malfunctions of the com-
pressor contactor (which may not be possible
with pilot duty motor protection).
Compressor overcurrent protection devices for
part winding applications must trip the first 3
legs in 2 to 6 seconds and the second 3 legs
in 1 to 3 seconds. Carlyle recommends a 1 to
1.25 second time delay between energizing the
first and second legs. Consult Carlyle
Application Engineering for part winding circuit
breakers. Part winding circuit breakers are
stocked in limited quantities by Carlyle and
may require special order.
ALLOWABLE OPERATING
Name Plate Frequency
Voltage
208–230
200
230
460
400
575
400
26
VOLTAGE RANGES
Min.
(Hz)
Voltage Voltage
60
187
50
180
50
198
60
396
50
342
60
495
60
342
Max.
264
230
264
528
456
660
460
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