FAQ's
Our Frequently Asked Questions (FAQ's) section is being regularly developed and added to. If you have a question but cannot find the answer, please either call or email us, or forward your question via our quick FAQ Form.
- What Hazards are created by Harmonics?
- What regulations control Harmonic levels?
- How can I measure Harmonic Distortion?
- How do I assess the extent of the problem caused by Harmonic Distortion?
- What type of equipment generates Harmonics?
- Are there any signs / indications other than measuring, to indicate I could have a Harmonic problem?
- Would doing nothing be an option?
- What options do I have to improve the Harmonic Distortion levels?
- What is the basic principal of the AIM Active Harmonic Filter?
- Why should I choose active harmonic filtering over other options?
- How would I select the correct AIM Filter for my requirements?
- What if additions to the load cause further harmonic distortion - will the AIM Filter be damaged by a greater level of harmonic distortion than originally measured?
- How would I select the installation location of the AIM Filter?
- Is the AIM Filter difficult to install?
- Is the AIM Filter difficult to commission?
- Does the AIM Filter need much on-going service and maintenance?
- Is everything included in the cost of the AIM Filter or are there any extras I would have to consider?
- What is the specification of the Current Transformers used with the AIM Filter?
- Are there any other options offered with the AIM Filter?
- Where can I find Technical Data on the AIM Filter?
- Where can I get information on applications where AIM Filters have been installed?
- What service and support do you offer your products?
- My question is not on the list - how can I get an answer to my question?
Answers
- What Hazards are created by Harmonics?
- Amplification of harmonic levels resulting from series and parallel resonance;
- Reduction of efficiency of power generation, transmission, and utilization;
- Aging of the installation of electrical plant components and as a consequence the shortening of their useful life;
- Plant mal-operation;
- Malfunctioning and failure of electronic equipment;
- Overheating and failure of electric motors;
- Overloading, overheating and failure of power factor correction capacitors. Resonance due to interaction of capacitors with harmonics;
- Overloading and overheating of distribution transformers and neutral conductors;
- Excessive measurement errors in metering equipment;
- Spurious operation of fuses, circuit-breakers and other protective equipment;
- Voltage glitches in computers systems resulting in lost data. Excessive flicker on VDU's;
- Electromagnetic interference with TV, radio, communication & telephone systems;
- Damage and disruption to standby generators and associated AVR control equipment;
- Interference with ripple control systems.
- What regulations control Harmonic levels?
In the UK the Engineering Recommendation G5/4 (2001) sets the planning levels of harmonic distortion to be used in the process for the connection of non-linear loads and recommends the total harmonic distortion should be below 5%.
The emission phenomena considered in this Recommendation are:
- Continuous harmonic, sub-harmonic and inter-harmonic voltage distortion within the range 0 to 2500Hz
- Short burst of harmonic distortion
- Voltage notching
In North America the Institute of Electrical Engineers recommends the standard IEEE 519-1992, which defines the maximum recommended voltage distortion (VTHD) for ‘general systems’ to be less 5%, with no more than 3% of any individual harmonic. This is to prevent system halt of some power sensitive equipment. IEEE 519-1992 also recommends control of current distortion (ITHD) under 5 classes of 5%, 8%, 12%, 15% and 20%.
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- How can I measure Harmonic Distortion?
Harmonic analysis is the process of calculating the magnitudes and phases of the fundamental and higher order harmonics of the periodic waveform.
Today we have true rms instruments from various manufacturers, that can provide all the information we need to consider the harmonic mitigation requirements. An example of such instruments would be BMI - 3030 1 or Fluke - 43B.
- How do I assess the extent of the problem caused by Harmonic Distortion?
If you have equipment such as those described in FAQ5. below, then harmonics will be present in the network to some degree or other. Signs indicating a serious harmonic problem include the premature failing of electric motors and transformers, cables overheating, spurious tripping of protection devices, and loss or corruption of computer data. (See FAQ1. for the more comprehensive list). To identify the full extent of the problem would require measurements to be taken at various locations close to the harmonic generators. These measurements can be taken using equipment such as those identified in FAQ3. or by bringing in a specialist to perform a site survey. The specialist will usually prepare a report which will identify the extent of the problem and will usually offer some suggestions to recover from the problem. AIM Europe offer this site survey service, please contact us for details.
- What type of equipment generates Harmonics?
Single-Phase:
- Computers, fax machines, photocopiers, UPS’s, TV’s, VCR’s, etc.;
- Lighting dimmers & electronic ballasts for high efficiency lighting;
- Single-phase AC & DC drives;
- Ultra-violet disinfection systems;
Three- Phase:
- Variable speed AC & DC drives;
- UPS systems;
- Arc furnaces & SCR temperature controllers;
- Battery chargers;
In fact any single or three phase electrical power conversion equipment which converts from AC to DC!
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- Are there any signs / indications other than measuring, to indicate I could have a Harmonic problem?
Signs indicating a serious harmonic problem include the premature failing of electric motors and transformers, cables overheating, spurious tripping of protection devices, and loss or corruption of computer data. (See FAQ1. for the more comprehensive list).
- Would doing nothing be an option?
Not addressing the problem can lead to unnecessary and costly disruptions in production and equipment failure, even ending in causing a fire. Addressing the problem can sometimes be expensive, but it usually ends up being the least expensive option.
- What options do I have to improve the Harmonic Distortion levels?
Methods of harmonic mitigation include:-
Phase Shifting;
Passive Filters;
Phase Staggering;
Active Filters.
Click here for fuller description of each.
- What is the basic principal of the AIM Active Harmonic Filter?
The AIM filter continuously monitors the harmonic current demanded by the load and generates an adaptive waveform which matches exactly the shape of the non linear portion of the load current. AIM injects this adaptive current into the load at the point of connection. Only fundamental (50Hz) current is drawn from the source by the load. The AIM Filter compensates from the 2nd to the 51st harmonic in a response time of less than 100 micro-seconds.
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- Why should I choose active harmonic filtering over other options?
AIM filters are the most technically advanced and effective solution in reducing the total harmonic current distortion to below 5%, in line with IEEE 519-1992 or UK Engineering Recommendation G5/4 harmonics standards.
The AIM Filter incorporates all of the following:- Harmonic mitigation; Reactive current control; Load side transient suppression; Load side surge suppression; Reduction in the effect of supply sags and surges (flicker). Providing 'Global harmonic compensation' from 2nd to 51st harmonic with a response time ~ 100 micro-seconds, the AIM Filter is especially suitable for dynamic loads.
The AIM Filter is fully adaptive, can be paralleled to achieve higher current ratings (up to 1000A) and will happily operate at maximum rated capacity. The AIM is easy to install, operate and maintain.
- How would I select the correct AIM Filter for my requirements?
To apply an AIM Filter a selection process must be performed. This process can be extensive or you can use a typical approximation method. AIM Europe suggests that ‘typical approximation’ will suffice 90-95% of the time when using AIM Filters. Only the AIM Filter permits use of a typical approximation method for sizing. Since the AIM Conditioner is a device which cancels more harmonic currents than any other device in the world, AIM Europe uses a very simplified process to insure that you meet the TVD internally, the TDD at the utility PCC, and the TCD for individual equipment. For detailed steps to sizing an AIM Filter, please refer to the General Product Information PDF download (231KB). Below is a summary of measurements and considerations:
- Size of AHF is based on the Harmonic Current
- Multiple loads one Filter; Size for total Harmonics
- VSD with 3% input line reactor; multiplier 0.35
- SCR with 5% input line reactor; multiplier 0.40
- Get one-line diagram indicating:
- Number of loads
- Type of Loads
- Redundancy
- Source impedance
- Take measurements via Instrumentation i.e. BMI-3030 1 or Fluke 43B
There are three standard voltage ratings of AIM Active Harmonic Filters - 208V / 380V / 480V.
There are seven current ratings of AIM Active Harmonic Filters - 25A / 50A / 100A / 150A / 200A / 300A / 400A. Higher ratings are achieved by paralleling AIMs (up to 1000A). For assistance sizing an AIM Filter please contact us. AIM Europe also offer full Harmonic Surveys, where your site is visited, measurements taken and results reported. To receive a quotation please contact us.
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- What if additions to the load cause further harmonic distortion - will the AIM Filter be damaged by a greater level of harmonic distortion than originally measured?
No, the AIM Filter is current limited and any harmonic current in excess of the AIM Filter rating will simply flow to the source. The AIM Filter will happily run in current limit all the time without any adverse effects, but the excess current flowing to the source may still effect other equipment that might be connected to the network. Dependant upon the size of the excess harmonic load current (say 15%) then an option might be to install an additional parallel AIM Filter to bring the THD down to an acceptable 5%. It will not be necessary to fit additional CT's if an additional AIM Filter is fitted as there is provision on the Signal Interface Board to use the original CT's.
- How would I select the installation location of the AIM Filter?
There are two schools of thought about the location of the AIM Filter, but both are right:
1. To locate at the Low Voltage (LV) Point of Common Coupling (PCC).
2. To position the AIM Filter as close to the 'source' of the harmonic loads as possible.
Option 1 is generally used where the main objective is to prevent the harmonic currents from migrating to the supply network and interfering with other customers on the supply network.
Option 2 is the most favoured location as this prevents the harmonics from interfering with other equipment in the same location and operating from the same transformer. In short it 'captures' the harmonics at the point of pollution and leaves the remainder of the system network free of harmonics.
- Is the AIM Filter difficult to install?
No. Because the AIM Filter is a parallel device it may not even be necessary to have ashutdown.The AIM Filter requires either 3 power cables (3Phase 3Wire) or 4 power cables (3Phase 4Wire) plus 2 CT's (3Phase 3Wire) or 3 CT's (3Phase 4Wire). The power cables require to be sized according to the total current injected by the AIM Filter and de-rated by 15% to accommodate the effects of the higher frequencies, i.e. skin effect. The CT's used (see FAQ18) are not ordinary instrument CT's as again, they are measuring higher frequencies than the 50Hz Fundamental and can be either ring type or split-core (extra cost). The CT cables require to be run separate from the power cables and preferably 'twisted pairs'. Local regulations may vary but generally a local 'isolation device' will require to be installed between the supply connection point and the AIM Filter if the distance between the connection point and the AIM Filter exceeds 1 meter (for safety reasons).
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- Is the AIM Filter difficult to commission?
No. Obviously there are procedures to follow but these are clearly identified in section 7 of the Installation and Operational Manual - Bringing the AIM Filter into Service. The AIM Filter is an analogue design so there is no lengthy programming to be done. Most of the set-up procedure involves the setting of switches to suit the application from the default position. However, some of the test points and status lights can only be accessed with the cabinet door open and although the AIM Filter has been built to comply with the EMC Low Voltage Directive, great care must be used as potentially lethal voltages are present. It is highly recommended that during commissioning two people are always present. To successfully commission an AIM Filter, the minimum instrument requirement would be an RMS Current meter with the preference being a Fluke 43B or equivalent. Fused test leads are also highly recommended for safety reasons.
- Does the AIM Filter need much on-going service and maintenance?
No. Dependant upon the environment that the AIM Filter is located only preventative maintenance would be required and that involves ensuring that the door and internal fans are fully operational and that all filters are free of dust and not blocked. It goes without saying that these preventative maintenance visits should include checks for any sign of overheating.
- Is everything included in the cost of the AIM Filter or are there any extras I would have to consider?
The enclosed AIM Filters are complete with MCS / Isolation device, operator interface, fans and filters and remote CT's. To operate only requires the customer to provide the power and CT cabling. However, Chassis versions would require the customer to provide the cabinet fans and filters, plus the MCS / Isolation device. Again power and CT cabling needs to be provided.
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- What is the specification of the Current Transformers used with the AIM Filter?
The current transformers (CT's) require to be chosen with great care as they significantly influence the performance of the AIM Filter.
Ratio: 2000:1 (alt. 1000:0.5 ; 3000:1.5)
Frequency Range: 50-400Hz
Class: 1
Burden: 5VA
Type: Ring or Split Core
Safety: Fitted with voltage clamping diodes
Please ask for our Current Transformer technical data sheet.
- Are there any other options offered with the AIM Filter?
Yes. We offer a fully integrated Power Quality Analyser (PQA) that can read individual harmonics up to the 18th and THD up to the 49th.The PQA can also be fitted with a communication module via RS485 serial link (2 or 3 wires) with JBUS / MODBUS or PROFIBUS DP protocol for use with a PC or PLC.
- Where can I find Technical Data on the AIM Filter?
The technical data is different for each frame size but we do produce a Technical Data Sheet for each frame size and configuration. Please ask.
- Where can I get information on applications where AIM Filters have been installed?
This is currently being compiled.
- What service and support do you offer your products?
Because the AIM Filter is a parallel device and is therefore not mission critical, we do not offer 24 hour service and support. However, we do supply a full service and support facility and carry spares for most frame sizes. See Service & Support page for further info.
- My question is not on the list - how can I get an answer to my question?
Go to our FAQ form. We will answer your question directly as quickly as possible.
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