Start Capacitors

Motor Start Capacitor

Electrolytic capacitors are employed in single phase induction motors in order to increase their starting torque.

It is necessary that such starting takes place in a fraction of a second and that once starting has occurred the capacitor is disconnected from the circuit by means of either a starting switch or relay.

The capacitive element is made of aluminium foils treated and separated by a leaf of impregnated paper as the electrolyte.

Cases are molded in a thermo setting material and terminals are 6.3mm Faston type.

Start Capacitor General Characteristics


Applications :   For A.C. Use. Starting of single phase motors.
Construction :   Etched aluminium foil.
Protection :   Moulded thermosetting plastic case. Sealing by rubber disk and bakelized paper. Safety Valve.
Terminals :   6.3 mm double 'Faston' type.
Mounts :   Via clips.
Start Capacitor Drawing

Please note: All motor start capacitors are fitted with double 6.2mm spade terminals.


Capacitor Value (mfd)Capacitor Dia. (mm) Capacitor Length (mm) Min. Mount Centres (mm)
30-38
40-50
50-63
60-75
70-88
80-100
100-125
125-156
150-188
200-250
250-313
36
36
36
36
36
46
46
46
52
66
66
86
86
86
86
86
86
86
112
112
112
124
36
36
36
36
36
38
38
61
61
61
61

Technical Characteristics

Reference Standards : VDE 560-8 : ASE 1029 : IMQ-CE1 33-3
Temperature : Operating Range: Lower Limit = - 25°C
Upper Limit = + 65°C
Capacitance Tolerance : 0 + 25%
Rated Voltage : 220/275 volts
Working Frequency Range : 50/60 HZ
Dissipation Factor : Average = 6%
Maximum = 10%
Duty Cycle : 3'/1.7% Hour Applications N = 20
Application Time
t = 3 seconds , Nxt = 60
i.e. 20 Starts per hour, 3 secs application time.
Extension of Duty Cycle : These capacitors withstand heavier duty cycles than the rated one. The table shows the maximum Nxt value (number of hour applications multiplied by application time) and the maximum admitted application time T max.
For temperatures below 55°C, the product Nxt and T max, can be multiplied by the following factors.
Ambient Temparature Factor : 55°C 45°C 35°C 25°C 15°C
1 1.25 1.5 1.75 2