FAQ

Can I use the same choke for use at the input or output of a drive?

We do not recommend this, as we believe this to be a compromise which leads to mediocre performance in either application.

KOSED produce line reactors, specifically for harmonic mitigation, transient suppression and general EMC use. These are usually of a higher inductance, than an output choke, for a given current, to ensure that the optimal harmonic reduction effect is achieved. Typically we manufacture inductors to give a 4% volts drop at the rated current, this level has been determined to provide the most cost effective performance although units with lower inductance are available. The laminations are standard thickness for mains 50/60 Hz operation as the voltage and other working parameters are well known.

On the other hand, KOSED’s range of DC Link Chokes is designed and manufactured to operate between the output of a frequency drive and the connected motor. Its inductance is usually rated to give a volts-drop which will not unduly affect motor performance, but at the same time provide the dV/dt limiting and motor terminal voltage reduction. The core is designed to operate at a lower flux density as inductor performance is severely affected at saturation. The laminations are thinner in order reduce the eddy current losses which occur due to the increased range of frequencies applied to the choke in normal operation.

Decide if I need to use a KOSED line(input) reactors with a Drive

The use of an input choke when used with a frequency drive has several benefits, reduction of harmonics and protection of the drive against transient voltages at the input side.

The drive manufactures installation guidelines should be adhered to but these are usually based on single drive applications without additional circuitry. In reality a PDS is made up from other equipment and maybe more than one drive and for this reason, harmonic reduction methods, such as a Line reactor should be considered.

Decide if I need to use a KOSED Load reactor also known as dv/dt reactor with a Drive

The nature of a Variable Speed drive and the PWM (Pulse Width Modulated) output it applies to a motor creates a number of potential issues.

Either a REO Motor Choke (CNW854) or a REO SineWave Filter (CNW933) will help to reduce the effects of the following:-

dv/dt, this is basically the rate of change of the voltage that appears at the motor terminals. This can cause a degradation of motor insulation, especially if the motor cable is beyond 10m

Reduced reflected wave phenomena, this is when the rise time of the PWM pulses is shorter than the time the pulse takes to propagate along the motor cable. In this case the voltages can be additive and there is a resultant increase in motor terminal voltage. This can damage drive insulation and cause the drive to trip.

Most drive switching frequencies are within the frequency range which is audible to humans – approximately 20 Hz – 20 kHz. In some instances, depending on motor mountings or characteristics, the motor will emit audible noise at the same frequency as the switching frequency.

Conducted EMC is reduced by fitting these products, especially in the case of the SineWave filter, CNW933.

In general the beneficial effects of a Sinewave filter will normally be greater than those for a motor choke in a given application, but a motor choke should be considered first as it usually represent the lowest cost option for most applications.

Problems with having sensitive equipment close to electrically noisy equipment

Electrically noisy equipment includes: mains switches, relays, contactors, DC motors, anything with an electromechanical contact that can spark, switch-mode power converters such as AC-DC power supplies and AC-AC variable-speed drives, mains transformers above 1kVA, thyristors and triacs, plasma displays, radio transmitters, etc.

Electrically sensitive equipment includes: transducer amplifiers, signal conditioners, microprocessors, cathode-ray-tube (CRT) devices such as VDUs, photomultiplier tubes, radio receivers, etc.

Spacings of at least one metre are preferred, whether we are considering noisy devices inside a cabinet or different cabinets.

Do you think a sample that you need is hard to make?

We have a top notch sampling process in this industry. You can be provided a perfect sample.

Please let me know, what dimension you need.

All the shipping that you order will be able to be free.

If you maintain working relationship (New customers) with us for 2 years, even all shipments of a new product that you want will be free. (CIF type) , (Oversea trade only)

But there is a compulsory quantity you have to order. It’ll be changed by a product cost. You can discuss that in purchase process.

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Can i use the same AC Reactors for use ar the input or output of a drive?

KOSED build input line reactors, specifically for harmonic mitigation, transient suppression and general EMI/EMC use. These are usually of a higher inductance, than an output choke, for a given current, to ensure that the optimal harmonic reduction effect is achieved. Typically we manufacture inductors to give a 4% volts drop at the rated current, this level has been determined to provide the most cost effective performance although units with lower inductance are available. The laminations are standard thickness for mains 50/60 Hz operation as the voltage and other working parameters are well known.

On the other hand, KOSED’s range of load reactors are designed and manufactured to operate between the output of a frequency drive and the connected motor.The core’s laminations are thinner in order reduce the eddy current losses which occur due to the increased range of frequencies applied to the choke in normal operation. Its inductance is usually rated to give a voltage-drop which will not unduly affect motor performance, but at the same time provide the dV/dt limiting and motor terminal voltage reduction. The core is designed to operate at a lower flux density as inductor performance is severely affected at saturation.

We can make so many different kinds rated current products. I hope our experience will help you to plan your projects.

Why do our engineers recommend line reactors?

Our team of experienced engineers recommends that all variable frequency drives should include reactors, at a minimum, for control of harmonics and power system pollution. Line reactors are the commonly preferred method of harmonic correction due to their effectiveness, reliability, and low cost. AC line reactors, or a combination of ac and dc reactors, will provide enhanced surge protection in addition to harmonic mitigation. Typical AC line reactors are 3% to 5% impedance, with the 5% models offering better harmonic control and better surge resistance, but at a slightly higher cost when compared to their 3% counterparts.

What role does a helical coil do?

A Hellical coil does much to improve reactor’s charicteristics. It brings down a internal temperature of reactors and stable

Helical wound coil helps cool down the reactor quicker and maintain an even temperature compared with the conventional coil that tends to have uneven temperatures and hot spots.

We conducted an experimental study using Ls (Inductance series) and Rs (Resistance series)  vs  Frequency Characteristics.

We found Helical wound coil is better than common wound coil. Helical wound coil exhibited spectacular frequency making it an ideal coil for maximum performance. It is also suitable for high frequency