Non-linear equipments generate harmonics as multiples of a fundamental frequency such as ac & dc motor speed controllers, arc furnaces, compact fluorescent lamps, uninterruptible power sources. As a result of this fact, besides the fundamental frequency, 3rd ,5th ,7th ,9th ... harmonics are generated.
Indications of Harmonics
- Excessive heating effect on electrical distribution equipment and cables
- Increased electrical insulation stress
- Increased noise in electrical motors
- Electronic mis-timings: Computers, fax machines etc.
- Capacitor overloads - premature failure
- Increased maintenance requirements and downtime
- Fluorescent light flickering
- Tripping of thermal circuit breakers unexpectedly.
The distortion limits determined by IEEE 519 standard are as follows:
Hospitals and Airports
Speed Control Equipments
: % THD (V) = 3
: % THD (V) = 5
: % THD (V) = 8
Most of the utilities impose high fees when certain level of harmonic distortion level is reached. Reactors with capacitors and sometimes with resistors creates a filter circuit tuned to a certain frequency in order to reduce, block or provide low impedance path for the harmonic currents in the audio frequency range.
Harmonic filtering reactors are connected in either parallel or a series configuration. Harmonic filters are normally installed in substations, in static var compensation and HVDC links.
Reactors are designed to meet specific design criteria such as Q factor, inductance tolerances etc.
Hilkar reactors can be equipped with off-load tapping to make a precise tuning at required frequency.
Power capacitors that are used in industrial plants in order to compensate reactive power can be used as filters besides being used for compensation. In order to prevent resonance in the systems, the value of inductance is selected approximately 20% different from the frequency of resonance which is :
The most commonly used filters are 189 Hz and 210 Hz filters. In these frequencies, XL / XC ratio which is called p factor is: %p = XL / XC = %7 and % 5.67 respectively. The harmonic values of six stroke loads are : I5 = 0.25I1, I7 = 0.13I1 , I11 = 0.09I1 .If an inductance is serial-connected to a capacitor (Qcn (kVAr)) in p value (XL / XC) at Ucn voltage, Qc which is effective reactive power flows to the network that has Un voltage is :
The inductance which resonates the Qcn capacitor at "fr" is: Ln = f.U2cn / 2 ∏fr2 .Qcn
Example : In order to transfer Qc = 50 kVAr to a Un = 400V network for a serial-connected capacitor to a reactor (%p = 7), a Ucn = 440V capacitor must be Qcn = 56.3 kVAr (or 525V, 80 kVAr). Thus, the terminal voltage of the capacitor is Uc = Un / (1-%P) = 400/(1-0.07) = 430 V.
Despite the fact that Ucn = 400V power capacitors are manufactured to resist 10% overloading and it is safe to use a 400 V capacitor for this example, Ucn = 440 V capacitors should be used in order to ensure complete safety.
Using a larger rated transformer than needed and using 12 stroke inverter instead of 6 stroke inverter reduces the harmonic distortion.
Network voltage in addition to the harmonic current :
Power capacitors use 300-400 times more current than normal at the moment of switching. In order to reduce this to 100 times, a serial-connected reactor with a p = 1% value can be used.
Specifications of 400 V Harmonic Filter Reactors
: fn = 50 HzNetwork Frequency
: Ih = 0.3 I1Maximum Harmonic Current
: I1 = ...AmpereFundamental Harmonic Current
: Ith = 1.1 I1 (p=7%) 1.2 I1 (p=5.67%)Heating Limit Current
: Ilin = 1,8 I1 (for iron core)Saturation Current
: Imax = 2 I1 (60 seconds)Maximum Current
: F ( 155 ° C )Insulation Class
: IP00Protection Degree
: 3000 V ac 1 minuteInsulation Withstand Voltage
- Increases equipment and capacitor life
- Perfect mechanical strength to withstand high short-circuit forces
- Limited temperature rise enables longer lifetime
- Special surface protection against UV and pollution Class IV areas
- Maintenance-free design
- Air core and iron core
- Dry type
- Side by side, delta or vertical arrangement depending on space availability for air core reactors
- Outdoor and indoor
- Single phase or three phase
- Enclosures are available on demand
- Aluminum or copper winding
- RAL 7035 or other colors
- - 40 ºC / + 55 ºC ambient temperature range
- F class (155 ºC) or customer specific design
- Taps are available
- Fiberglass resin spacers are used in order to provide ease of cooling
- AN (air-natural) cooling method
K6 = 6 mm2 connector
P8 = Metric 8 terminal
P10 = Metric 10 terminal
IEC 600076-6 or depending on customer requirements.
- F class (155 ºC) film insulation and epoxy resin reinforced fiberglass
- Insulating varnis & corrosion resistant paint
Aluminum, hot dip galvanized steel or concrete support stands are designed for specific applications.
All the routine tests are performed in accordance with EN 60289 or other standards depending on customer request. Type test reports are available on request. All the test reports are submitted to customer.
Basic testing program includes some or all of the following tests:
- Routine Tests (Inductance, Resistance, One Minute AC Insulation Voltage Withstand Test and Impulse Voltage Withstand Test)
- Short Circuit Withstand Test
- Temperature Rise Test
- Sound Level Test
- Seismic Test
Linearity of Reactor
All Hilkar reactors are computer designed in order to minimize investment and operating losses.
Hilkar maintains a complete quality assurance program including ISO 9001 and other European and American Standards in it's manufacturing plant.
The height and the diameter of the reactor can be adjusted to customer specific needs in order to meet unusual space requirements.
Complete installation guidelines are provided with the reactors in order to meet required magnetic clearances on close metallic structures. Each reactor is supplied with an installation guidelines that specifies minimum magnetic clearances for the reactor.
Hilkar provides complete technical assistance to contractors and end customers for applications, design, calculations and field installation. All Hilkar reactors are custom designed for different applications by considering the voltage, current, inductance, size, loss characteristics that are required to provide the most efficient design at the most economical prices.