Mallory PSU Application Guide

Type PSU Motor Start CapacitorsApplication Guide

VOLTAGE RATING

The capacitors's rated voltage must be greater than or equal to
the average voltage across the capacitor' s terminals during the mo­tor starting cycle. This is not the same voltage as the motor
line voltage. In addition, the cutoff voltage rating of the capaci­tor must be greater than or equal to the maximum voltage attained
across the terminals of the capacitor in actual service.

The maximum recommended cut-off voltages for the four stan-

dard voltage ratings are as follows:

Rated Maximum

Voltage (rms) Cut-Off Voltage (rms)

125 160
165 210
250 300
330 400

These ratings are based on the maximum capacitor temperature
of 65 ºC.

CAPACITANCE RATING

The capacitance is chosen to give the necessary starting torque to
the motor. The minimum capacitance value is the minimum de­signed capacitance. The maximum capacitance is 20% more than
the minimum value.

Duty Cycles of Type II

Table A

Rate d

Voltag

V

(rm s

125

165

250

330

Typical life expectancy is 50,000 cycles for 125V ratings, and 40,000
total cycles for 165, 250 and 330V ratings. The number of cycles
shown in the table above are for the convenient test time of 35 days

total for all ratings.

Capacitance

Rating (µF)

e

AC

From To

)

21-25 81-106 0.75 29.25 2.500 50,000
108-130 145-174 1 59 1.670 50,000
161-193 233-280 1 89 1.110 33,500
243-292 378-454 1 119 0.833 25,000
400-480 590-708 1 179 0.556 16,500
645-774 800-960 1 239 0.417 12,500

21-25 88-106 1 59 1.670 33,500
108-130 124-149 1 89 1.110 33,500
130-156 216-259 1 119 0.833 25,000
233-280 340-408 1 179 0.556 16,500
378-454 590-708 1 239 0.417 12,500

21-25 30-36 1 59 1.670 33,500

36-43 64-77 1 89 1.110 33,500

72-86 88-106 1 119 0.833 25,000
108-130 189-227 1 179 0.556 16,500
216-259 324-389 1 239 0.417 12,500

21-25 21-25 1 59 1.670 33,500

25-36 30-36 1 89 1.110 33,500

36-43 64-77 1 119 0.833 25,000

72-86 88-106 1 179 0.556 16,500
108-130 130-156 1 239 0.417 12,500

Duty Cycle

Secs.

Secs.

(On )

(Off)

Duty

Cycle

%

#

of

Starts

DUTY CYCLE

The duty cycle should be calculated for each application. It is the
ratio of the time the capacitor is on voltage to the total time of one
cycle. The duty cycles for the normal performance of standard Type
II capacitors are listed in Table A. CDE type PSU capacitors may be

used in any intermittant application within their temperature and
voltage range where the duty cycle does not exceed that listed in Table

A. This is in accordance with the standards in EIA Specification
RS-463 for Type II capacitors. If a particular application exceeds the
normal duty cycle, but does not exceed the values listed in Table B,
an extra performance or Type I capacitor is required.

FREQUENCY

These capacitors are designed for 60 Hz application but may

be operated in the range of 47 Hz - 60 Hz without damage provided
voltage limitations stated above are observed. For other variations
in frequency, contact CDE.

Duty Cycles of Type I

Table B

Rate d

Voltag

V

(rm s

125
165
250
330

If an application exceeds the duty cycles of Type I, other methods of
capacitor selection must be used. Contact CDE, for Engineering

assistance.

e

AC

)

Capacitance

Rating (µF)

all
all
all
all

MOUNTING

Vertical mounting of the capacitor with the terminals
up is recommended. However, horizontal mounting is

acceptable providing the vent is in the upward position.
Vertical mounting with the terminals down is not
recommended because the capacitor life may be reduced.

Duty Cycle %

Secs.

(On )

0.75 29.25 2.500 75,000
1 59 1.670 40,000
1 59 1.670 40,000
1 59 1.670 40,000

Secs.

(Off)

Duty

Cycle

#

of

Starts

CDE Cornell Dubilier•1605 E. Rodney French Blvd.•New Bedford, MA 02744•Ph: [phone]•Fax: [phone]• www.cde.com