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Application

Capacitors for power electronics can be used for a wide variety of applications, even where extremely non-sinusoidal voltages and pulsed currents are present. Both AC and DC capacitors are available. AC capacitors are periodically recharged during operation, DC capacitors are periodically charged and discharged without recharge.

AC capacitors serve as damping or snubbing capacitors connected in series with a resistor, and are designed for the damping of undesirable voltage spikes caused by the so-called carrier storage effect during the switching of power semiconductors. When applied as commutation capacitors, they are switched in parallel to a thyristor and designed to quench its conductive state. Since commutating capacitors are periodically and abruptly recharged, the peak current will substantially exceed the rms value.

Further, AC capacitors are used in low-detuned or close-tuned filter circuits for filtering or absorbing harmonics. As pulse discharge capacitors, they are useful in applications with reversing voltages, e.g. in magnetizing equipment.

Series E62, E53 and E62/276 in this catalogue have been designed for AC use. Further, specially adapted from the E51 and E56 ranges are available for AC applications on request.

The scope of application for DC capacitors is similarly diverse:
Smoothing capacitors serve for the reduction of the AC component of fluctuating DC voltage, e.g., in power supplies in radio and television technology (transmitters), high voltage testing equipment, DC controllers, measurement and control technology, cascaded circuits for generation of high DC voltage a.m.o. Supporting capacitors, DC-Filter or buffer circuit capacitors are used for energy storage in intermediate DC circuits, e.g. in frequency converters for poly-phase drives, transistor and thyristor converters. They must be able to absorb and release very high currents within short periods, the peak value of the current being substantially greater than the rms value.

Surge (Pulse) discharge capacitors are also capable of supplying or absorbing extreme short-time current surges. They are usually operated in discharge applications with non-reversing voltages, and at low repetition frequencies, e.g. in laser technology and lighting generators.

In this catalogue, series E61, E63, E50, E51, E56, but also E62 and E53, can be used for DC applications.

Definitions and Selection Criteria

The terms and abbreviations used in this catalogue are based mainly on the actual standard for power electronics capacitors, IEC1071 / EN61071.

Rated capacitance CN

Capacitance value rated at 20°C / 50 Hz.

Non repetitive peak (surge) voltage Us

Voltages beyond the rated voltage induced by switching or faults of the system or any part of it. Maximum count 1000 times with a duration of not more than 50 ms each.

rms voltage Ueff

Root mean square of the max. permissible value of sinusoidal Ac voltage in continuous operation.

Ripple voltage Ur

The peak-to-peak alternating component of the unidirectional voltage.

Voltage test between terminals UBB

Routine test of all capacitors conducted at room temperature, prior to delivery. A further test with 80% of the test voltage stated in the data sheet may be carried out once at the user's location.

Voltage test between terminals and case UBG

Routine test of all capacitors between short-circuited terminals and case, conducted at room temperature. May be repeated at the user's location.

Insulation voltage Ui

Rms value of the AC voltage for which the terminals to case insulation has been designed and tested. If not stated in the data sheets, the insulation voltage is at least

Rate of voltage rise (du/dt)max

Maximum permitted repetitive rate of voltage rise of the operational voltage.

Î= CN x (du/dt)max

Maximum non-repetitive rate of voltage rise (du/dt)s

Peak rate of voltage rise that may occur non-repetitively and briefly in the event of a fault.

ls = CN x (du/dt)s     ls = non-repetitive peak current

Maximum current Imax

Maximum rms value of permissible current in continuous operation. The values given in the data sheets are related to either the specified maximum power dissipation or the current limits of the connection terminals.

Peak current Î

Maximum permitted repetitive current amplitude during continuous operation.

Non-repetitive peak current (surge) ls

Maximum current that may occur non-repetitively and briefly in the event of a fault. Maximum count 1000 times with a duration of not more than 50 ms each.

Equivalent series resistance Rs

Equivalent resistance representing the sum of all Ohmic resistance occurring inside the capacitor. Essential for calculation of the current dependent losses.

PVR = l2eff x Rs    PVR = current dependent losses

Self-inductance Le

Represents the sum of all inductive elements which are - for mechanical and construction reasons - contained in any capacitor.

Resonant frequency fres

The capacitance and self-inductance of any capacitor form a series resonant circuit. Above the resonant frequency, the inductive part of this LC-circuit prevails. The capacitor would then behave as in inductor.

Dielectric dissipation factor tanδ0

Constant dissipation factor of the dielectric material for all capacitors in their rated frequency.

Thermal resistance Rth

The thermal resistance indicates by how many degrees the capacitor temperature at the hotspot rises in relation to the dissipation losses.

Maximum power dissipation Pmax

Maximum permitted power dissipation for the capacitor's operation.

HOTSPOT = hotspot temperature

U = ambient temperature

Rth = thermal resistance

Ambient termperature Θu

Temperature of the surrounding air, measured 10 cm away and at 2/3 of the case height of the capacitor.

Lower category temperature Θmin

Lowest permissible ambient temperature at which a capacitor may be used.

Upper category temperature Θmax

Highest permissible capacitor temperature during operation, i.e. temperature at the hottest point of the case.

Hotspot temperature ΘHOTSPOT

Temperature at the hottest spot inside the capacitor.

Rated energy contents WN

Energy stored in the capacitor when charged at rated voltage.

WN =

Humidity class C

Max. relative humidity 95% annual means, 100% occasional, condensation permitted.

Humidity class F

Max. relative humidity 75% annual means, 95% 30days/year, condensation not permitted.

Clearance in air L

The shortest diatance between conducting parts of the terminals or between terminals and case. In this catalogue, we state only the shorter.

Creepage distance K

The shortest distance along an insulated surface between conducting parts of te terminals or between terminals and case. In this catalogue, again we state only the shorter.

Mounting and Operating Instructions

Safe operation of the capacitors can be expected only if all electrical and thermal specifications as stated on the label, in the data sheets or catalogues and following instructions are strictly observed.

ELECTRONICON does not accept responsibility for whatever damage may arise out of a non-observance.

Mounting Position

MKP capacitors with liquid or viscous filling shall be installed upright with terminals facing upwards. Please consult our technical department if different mounting position is required. Capacitors with solidified resin filling can be mounted in any position without restrictions.

Mounting Location/Cooling

The useful life of a capacitor may be reduced dramatically if exposed to excessive heat. Typically an increase in the ambient temperature of 7°C will halve the expected life of the capacitor.

To avoid overheating the capacitors must be allowed to cool unhindered and should be shielded from external heat sources.

If attenuating circumstances give cause for doubt, special tests should be conducted to ensure that the permitted maximum temperature of the capacitor is not exceeded even under the most critical ambient circumstances. It should be noted that the internal heat balance of large capacitors is only reached after a couple of hours.

Give at least 20 mm clearance between the capacitors for natural or forced ventilation.

Do not place the capacitors directly above or next to heat sources such as detuning or tuning reactors, bus bars, etc.

Vibration Stress According to DIN IEC 68-2-6

The capacitors comply with test standard FC acc. To DIN IEC 68 pt. 2-6 as follows:

Capacitor Weight Test Duration Frequency Range Max. Acceleration Max. Displacement Amplitude
<0.5 kg 30 cycles 10 … 500Hz 50 m/s2 0.35 mm
0.5 … 3 kg 30 cycles 10 … 500Hz 10 m/s2 0.075 mm
> 3 kg Information available on request

All cylindrical capacitors can be fixed sufficiently using the mounting stud at the base of the can. It is recommended to insert the washer which is delivered together with the mounting nut before fixing the nut.

Connection

The soldering must not be exposed to excessive heat. It is not recommended to solder cables to the terminals. Where possible use appropriate tab connectors to connect the cables.

Do not bend or turn or move the connecting terminals and the tab connectors in any way.

Connection at threaded studs shall be made between two nuts. During connection the lower nut shall be backed up to avoid any transmission of the torque above the a.m. figures to the ceramic body.

M5 1.5 Nm
M6 2 Nm
M10 7 Nm
M12 10 Nm
Screw Terminal Type L (M5) 2.5 - 3 Nm
Screw Terminal Type M (M6) 3.2 - 3.7 Nm
M6 Internal Thread 4 Nm
M8 Internal Thread 7 Nm

Capacitors with break-action mechanism shall be connected with sufficiently flexible leads to permit the functioning of the mechanism, and sufficient clearance for expansion of the capacitor case must be accommodated above the terminals. Depending on the specific dimensions of the capacitors the case could expand between 5 and 25 mm.

  • The capacitors shall only be connected with flexible cables or elastic copper bands.
  • The folded crimps must not be held by retaining clamps.
  • ATTENTION: Required minimum clearances according to applicable voltage category must be maintained even after prolongation of the can!

The hermetic sealing of the capacitors is extremely important for a long operating life and for the correct functioning of the break action mechanism. Please pay special attention not to damage the following critical sealing points:

  • the bordering of the lid
  • the connection between screw terminal and lid (design L,M)
  • the rubber seal at the base of the tab connectors (design D, E)
  • the soldering at the base of the tab connectors (design B, D, E)
  • the ceramic insulators (design C)

Do not hit the bordering and the connecting terminals with heavy or sharp objects or tools (e.g. hammer, screw driver).

Discharge

If there is no discharge of the capacitors provided by external circuits, the capacitors should be provided with discharge resistors. In any event, the poles of the capacitors must be short-circuited before being touched. Note that capacitors with nominal voltages above 750 V in particular may regenerate new voltage at their terminals after having been short-circuited just for short periods. This condition results from the internal series connection of the capacitor elements and will be avoided by storing them permanently short-circuited.

Earthing

Capacitors with a metal case must be earthed at the mounting stud or by means of a separate metal strap or clamp.

Environment Hazards

Our capacitors do not contain PCB, solvents, or any other toxic or banned materials. They do not contain hazardous substances acc. To <<Chemishe Verbotosverordnung>> (based on European guidelines 2003/53/EG and 76/769/EWG), <<Gefahrstoffverordnung>> (GefStoffV) and <<Bedarfsgeneenstaendeverordnung (BedGgstV>>.

Not classified as <<dangerous goods>> acc. To transit rules. The capacitors do not have to be marked under the Regulations for Hazardous Goods. They are rated WGK 0 (water risk category 0 <<no general threat to water>>).

No danger for health if applied properly. In case of skin contact with filling liquids, clean with water and soap.

All capacitors manufactured after January 1, 2006 are made with lead-free solder tin.

Disposal

The impregnants and filling materials contain vegetable oil or polyurethane mixtures. A data sheet about the impregnant utilized can be provided by the manufacturer on request.

We recommend disposing of the capacitors through professional recycling centers for electric/electronic waste.

The capacitors can be disposed of as follows:

  • Disposal acc to European Waste Catalogue 160205 (capacitors filled with plant oil/resin).
  • Hardened filling materials: acc. To EWC 080404 (<<solidified adhesives and sealants>>).
  • Liquid filling materials which may have emerged from the capacitor shall be absorbed by proper granules and disposed of in accordance with European Waste Catalogue 080410 (PUR resin residues, not solidified).

Caution: When touching or wasting capacitors with activated break-action mechanism, please consider that even after days and weeks these capacitors may still be charged with high voltages!

Consult your national rules and restrictions for waste and disposal.

Protection Against Overvoltages and Short Circuits: Self-Healing Dielectric

All dielectric structures used in our power capacitors are "self-healing": In the event of a voltage breakdown the metal layers around the breakdown channel are evaporated by the temperature of the electric arc that forms between the electrodes. They are removed within a few microseconds and pushed apart by the pressure generated in the centre of the breakdown spot.

An insulation area is formed which is relatively resistive and voltage proof for all operating requirements of the capacitor. The capacitor remains fully functional during and after the breakdown.

Protection Against Accidental Contact

All capacitors are checked by routine test: voltage test between shorted terminations and case in accordance with IEC1071. Accessible capacitors must be earthed at the bottom stuff or with an additional earthling clamp.

The terminal block of designs L1, L3, M1 and M3 is rated IP20, i.e. it is protected against accidental finger contact with live parts. All other capacitors are not protected against accidental contact.

Protection Against Overvoltages and External Short Circuits

As shown above, the capacitors are self-healing and regenerate themselves after breakdowns of the dielectric. For voltages within the permitted testing and operating maximum the capacitors are overvoltage-proof. They are also proof against external short circuits as far as the resulting surge discharges do not exceed the specific current limits (ls).

1.1 x UN 30% of the service period
1.15 x UN 30 min/d
1.2 x UN 5 min/d
1.3 x UN 1 min/d
1.5 x UN 100 ms/d

Protection Against Overload and Failure at the End of Useful Service Life

In the event of overvoltage or thermal overload or ageing at the end of the capacitor's useful service life, an increasing number of self-healing breakdowns may cause rising pressure inside the capacitor. To prevent it from bursting, the capacitors of series E62, E63 and 276 are fitted with an obligatory <<break action mechanism>> (BAM). This safety mechanism is based on an attenuated spot at one of the connecting wires inside the capacitor. With rising pressure the case begins to expand, mainly by opening the folded crimp and pushing the lid upwards. As a result, the prepared connecting wire is separated at the attenuated spot, and the current path is interrupted irreversibly.

It has to be noted that this safety system can act properly only within the permitted limits of loads and overloads.

MIND HAZARDS OF EXPLOSION AND FIRE

Capacitors consist manly of polypropylene (up to 90%), i.e. their energy content is relatively high. They may rupture and ignite as a result of internal faults or external overload (e.g. temperature, overvoltage, harmonic distortion). It must therefore be ensured, by appropriate measures, that they do not form any hazard to their environment in the event of failure or malfunction of the safety mechanism.

FIRE LOAD: appox. 40MJ/kg

EXTINGUISH WITH: dry extinguisher CO2, foam

Dielectric

MKP-type capacitors are based on a low-loss dielectric formed by pure polypropylene film. A thin self-healing mixture of zinc and aluminum is metallized directly on one side of the PP-film under vacuum. In some cases, additional unmetallized layers are added between the metallized ones.

The plastic film is wound into stable cylindrical windings on the most modern automated equipment. The ends of the capacitor windings are contacted by spraying with a metal contact layer, facilitating a high current load and ensuring a low-inductance connection between the terminals and windings.

Our long-term experience as well as on-going research and improvements in this technology ensure the excellent self-healing characteristics of the dielectric and a long operating life of our capacitors.

Impregnants

The use of filling materials in capacitors is necessary in order to insulate the capacitor electrodes from oxygen, humidity, and other environmental interference. Without such insulation, the metal coating would corrode, an increasing number of partial discharges would occur, the capacitor would lose more and more of its capacitance, and suffer increased dielectric losses and a reduced operating life.

Therefore, an elaborate vacuum-drying procedure is initiated immediately after insertion of the capacitor elements into the aluminum case and biologically degradable plant oil or solidifying PUR resin is introduced. Both protect the winding from environmental influence and provide an extended life-expectancy and stable capacitance.