305C21 Datasheet, PDF (4/6 Pages) Vishay Siliconix – PTCR Motor Start Packages PSC Single Phase Motor Start Assist

305C Series
Vishay Cera-Mite
PTCR Motor Start Packages
PTCR SELECTION
• Choosing the best PTCR for an application is a simple
matter. See Table 4 and Table 2. Vishay Cera-Mite PTCRs
are available in three case sizes (A, B, and C).
• Table 4 indicates the correct case size for the application.
Table 2 shows how to choose the correct resistance
value.
• Using a device too small or resistance too high
will give inadequate starting performance. An oversize
device will not harm the motor, but may not be optimum with
regards to acceleration dynamics, or power dissipation.
• The PTCR is generally self protecting when applied within
the voltage and current ratings.
Table 4
PTCR MOTOR START SELECTION CHART
VISHAY
CERA-MITE
PART CASE
NUMBER STYLE
RESISTANCE (OHMS)
R_DYN
R₀
± 20%
± 30%
SWITCH TIME
(T) SECONDS
@ 230V
CURRENT MAX. VOLTAGE AVG. POWER
COMPRESSOR
RATING
RATING
DISSIPATION
RANGE
AMPERES VOLTS, RMS
WATTS
BTU (000)
HP
305C20* C
25
35
0.25
10
410
305C21 C
35
50
0.35
8
410
305C22* C
50
75
0.50
6
410
305C19* B
20
30
0.50
18
500
305C12* B
25
40
0.60
15
500
305C2 B
50
85
1.00
12
500
305C9* A
10
15
0.50
36
500
305C11 A
12.5
20
0.60
30
500
305C1* A
25
42.5
1.00
24
500
3.5
10 - 28
0.75 - 2.0
3.5
8 - 18
0.5 - 1.5
3.5
5 - 12
0..25 - 1.0
7
20 - 50
1.5 - 4.0
7
18 - 42
1.5 - 3.5
7
10 - 25
1.0 - 2.5
9
28 - 68
3.0 - 7.0
9
28 - 62
3.0 - 6.0
9
14 - 36
1.5 - 3.5
Note 1
Note 2
Note 3
Note 4
Note 5
Note 6
Note 7
* Preferred Values
Note 1
Part number is stamped on the device
for UL recognition. The customer
part number will also include 1 or
3 character alpha-numeric suffix to
designate mounting bracket, customer
marking, wire jumper, or other acces-
sory furnished.The suffix is not marked
on the part. Certified outline drawing
and complete part number will be
furnished on request for specific
applications. (Example: 305C19K01.)
Mounting brackets and other acces-
sories are shipped in separate boxes
to simplify installation in end use
equipment.
Note 2
R_DYN is nominal resistance equal to E/I
when 230 volts, 60 Hz is applied (See
Fig T-7). This resistance determines
current and starting torque at the
moment of application of voltage to
the motor and can be measured with
an oscilloscope.
For receiving inspection or routine
trouble shooting, the D.C. resistance
(Ro) as measured with an ohmmeter
is approximately 50% greater. For
example: 305C20 measured with an
ohm meter would be 35 ohms ± 30%
tolerance.
Note 3
Resistance values are duplicated in
several case sizes (ie: 305C20, C12,
and C1) to provide longer switch time
(t) and higher current ratings (See
Fig T-7). Larger parts may be needed
for more difficult starting conditions
(voltage or temperature) or may be
used for accelerating fans against
back pressure.
Note 4
Maximum current in the PTCR is
determined by
Max Line Voltage
Min R_DYN
Motor auxiliary winding impedance
is usually small compared to PTCR
resistance, and does not materially
affect PTCR current.
Current in PTCR is a percentage of
the full motor inrush (locked rotor)
current; usually 30% to 50% (See
Fig T-5).
Note 5
In application, the maximum voltage is
the voltage that appears across the
run capacitor at rated speed, high line,
light load. This is not the applied line
voltage (See Fig T-6).
THESE DEVICES ARE INTENDED
FOR APPLICATION ON 240 VOLT
LINES OR SYSTEMS WITH MAXI-
MUM LINE VOLTAGE UP TO 264
VOLTS. The 305C20, 21 and 22 are
also used on 120 volt systems where
the motor is designed to use same
run capacitor and PTCR as equivalent
230 volt compressor.
Note 6
This is the power used to keep the
PTCR switched off under full load
running conditions at typical ambient
temperature.
Note 7
BTU and horsepower ranges are
for reference only. PTCR may be
applied outside those ranges as long
as maximum voltage and maximum
current are not exceeded. Scroll
and rotary compressors may require
less starting assistance allowing use
of smaller devices.
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Document Number: 23086
Revision 14-May-02