Application Note

VISHAY BCCOMPONENTS
www.vishay.com
Aluminum Capacitors
Application Note
Aluminum Electrolytic Capacitors for Traction Applications
By Theo van de Steeg, Jules Spanjaars, and Harm van Driel
INTRODUCTION TO THE APPLICATION
Traction is a blanket term for applications in trains or “rolling stock.” Both the electrical propulsion systems as well as the
electrical systems supporting the brakes, lighting, and power supply are focus areas included in this application category.
SELECTING THE BEST CAPACITOR FOR YOUR TRACTION APPLICATION
Aluminum electrolytic capacitors are used in two main traction applications:
• As DC-link capacitors in traction drives used to control the speed of large electrical motors
• As DC-link capacitors in auxiliary power supplies in rolling stock, e.g. for air conditioning
In both applications the aluminum capacitor is used as an energy buffer to ensure stable operation of the switch mode inverter
driving the motor or auxiliary power circuit. The aluminum capacitor also functions as a filter to prevent high-frequency
components from the switch mode inverter from disturbing the board net.
The key selection criterion for the aluminum capacitor is the needed ripple current, which corresponds to the 8 kHz to 20 kHz
high-frequency ripple currents generated by the inverter.
To maximize its operating life, the aluminum capacitor should be located on the coolest possible location. Forced cooling or
mounting of the capacitor on a heatsink will increase component lifetime, especially in combination with the extended cathode
construction inside the aluminum capacitor.
It is advisable to specify a minimum capacitance to ensure stable operation of the drive. A low inductance (ESL) also improves
the filtering of switching noise. ESL values below 13 nH can be reached for screw-terminal devices in large case sizes.
Both series and parallel connections are commonly used with aluminum capacitors, as the voltages in rolling stock may well
reach up to 1200 V. In such cases three aluminum capacitors can be used in series. Care should be taken to balance the
intermediate voltage between the capacitors, usually with so called bleeder resistors (also available from Vishay).
For higher voltage ranges or higher power applications, power film capacitors, also available from Vishay, are the best option.
Document Number: 28412
1
For technical questions, contact: aluminumcaps2@vishay.com
THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT
ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000
APPLICATION NOTE
Revision: 25-Sep-14
Application Note
www.vishay.com
Vishay BCcomponents
Aluminum Electrolytic Capacitors for Traction Applications
OUR SOLUTIONS
For this kind of application we highly recommend our 110 PHT-ST series. This series is designed for use in traction applications
and offers high ripple current capabilities along with long lifetimes. Our experience with screw terminals goes back beyond
1988, at that time under the brand name of Philips.
Typical examples in the traction market are:
VOLTAGE
Capacity
(case size)
250 V
300 V
350 V
400 V
450 V
20 000 μF
(Ø 76 mm x 220 mm)
6000 μF
(Ø 76 mm x 220 mm)
6000 μF
(Ø 76 mm x 220 mm)
15 000 μF
(Ø 90 mm x 220 mm)
10 000 μF
(Ø 90 mm x 220 mm)
27 000 μF
(Ø 76 mm x 220 mm)
18 000 μF
(Ø 76 mm x 220 mm)
12 000 μF
(Ø 76 mm x 220 mm)
16 000 μF
(Ø 90 mm x 196 mm)
Our products have been approved for use in OEM applications and as replacement parts for existing rolling stock in drives from
diverse manufacturers, such as AEG, Alstom, GE, and Siemens.
In refurbishment projects, realizing mechanical exchangeability and providing engineering support to select the best
replacement are key characteristics when the decision is taken to not work with the OEM supplier. We can offer customized
products based on your needs, with temperature ranges from 85 °C to 105 °C and lifetimes from 2000 h to 15 000 h at maximum
temperatures. A lifetime of 100 000 h at 70 °C is another standard guideline that is reachable with our professional components.
We can provide lifetime calculations to support the capacitor's performance for the given lifetime in your application.
Terminations are available from metric M5-8 mm to M6-18 mm, as well as U.S. tread ¼-28 UNF. Screws and washers are
supplied with the capacitors.
3-Phase IGBT Power Stage
3-Phase
Filter
CurrentCompensated
Choke
and
X-Capacitors
and
Y-Capacitors
DC Link
Rectifier
Bridge
Induction Motor
3-Phase
Film Capacitors
Y-Capacitors
DC-Link Capacitor
APPLICATION NOTE
A typical block diagram of the application
Revision: 25-Sep-14
Document Number: 28412
2
For technical questions, contact: aluminumcaps2@vishay.com
THIS DOCUMENT IS SUBJECT TO CHANGE WITHOUT NOTICE. THE PRODUCTS DESCRIBED HEREIN AND THIS DOCUMENT
ARE SUBJECT TO SPECIFIC DISCLAIMERS, SET FORTH AT www.vishay.com/doc?91000