Please find below, a selection of the commonly asked queries we receive, if you cannot find the answer to your question here, or would like further information please contact our office on 0115 9441036 or email

Inverter FAQs

Q. My Inverter won’t work, why?
A. There could be a number of contributing factors as to why your inverter is not working. To enable us to assist you with your issue please contact one of our engineers on 0115 9441036 or e-mail

Q. What advantage is there in using an inverter to control a motor?
A. An inverter can vary the motor speed with no loss of efficiency, the resulting energy savings usually pay for the inverter in a relatively short period of time. In addition the motor only works as hard as it needs to so helping to prolong the life of the motor.

Q. How will an Inverter affect my power factor?
A. ABB Inverters run at near unity power factor so there will always be an improved power factor with an inverter, especially when the motor is lightly loaded.

Q. Do inverters create harmonics? If so are they a problem?
A. All standard inverters create 5th and 7th harmonic frequencies, however in the vast majority of applications ABB inverters do not cause any problems. Occasionally, and this depends on the applications there may be issues and harmonics can cause problems such as transformer heating. We can predict and analyse these for you. Click on the link to take a look at our video: if this doesn’t answer your query, please call one of our engineers on 0115 9441036 or if it is out of office hours and you do not currently have a maintenance contract with us please email

Q. What level of electro-magnetic filtration do I require for my inverters?
A. If you share a supply transformer, then you require first environment filters; if you have your own transformer then you require second environment filters which are fitted to ABB inverters as standard.

Q. How will an inverter save me money?
A. In simple terms, inverters are used to vary the speed of the motor to match the required load. Please refer to our video which will help you to see how fitting an inverter will save you energy and therefore save money on your energy bills. Book a free energy survey here and find out how much we can save you!

Q. How efficient is an inverter?
A. Typically 98% at full load.

Q. Can you explain the IP ratings?

Q. How much energy will an inverter save?
A. The answer depends on the way the inverter is be used , here are a few examples we hope you will find useful:

Air compressors 10-15%
Hydraulic power packs 10-15%
Extract fans – up to 50%
Supply fans – up to 50%
DC Motor replacement – 10-15% plus significantly reduced motor maintenance costs.

Q. Sometimes on really hot days my pumps can’t cope, Can I speed them up?
A. Yes, one of the advantages of inverters is that they can make the motors speed up beyond what it would normally work at. This is really a short term fix as energy consumption will rise significantly.

Q. What is sensorless vector control?
A. Sensorless vector control is a variable frequency drive (VFD) control strategy that improves motor performance by regulating the VFD output based on a mathematical determination of motor characteristics and operating conditions. Operating conditions are estimated from measurements of electrical parameters. Sensorless vector control is called “sensorless” to distinguish it from vector control with encoder feedback which optimizes motor performance by regulating the VFD output based on motor shaft speed and position feedback from an encoder.

Q. The term inverter is a little confusing, since we also use drive and amplifier to describe the electronic unit that controls a motor. What does inverter mean?

Q. What type of motor is compatible with inverters?
A. Motor type – it must be a three phase AC induction motor. Preferably, use an inverter or vector duty motor that has 800V insulation for 200V class inverters, or 1600V insulation for 400V class. With regard to motor size, in practice, it is better to find the right size motor for your application; then look for the inverter to match the motor.

Q. How will I know if my application will require resistive (dynamic) braking?
A. If you try and stop a motor when it is loaded, particularly for an application like an indexing conveyor, mixer or centrifuge, and simply remove the power it will coast along until the mechanical limits of the system cause it to stop. This is fine if you can wait all day! If your load has a high inertia (i.e. it takes a lot of effort to make it change direction or speed) and you require it to come to a stop or slow down within a certain time or at a certain rate then braking resisters may be the answer. Braking resisters are simply a way of getting rid of the excess energy that controlled braking can generates. If you require advice on sizing your brake resister, give IDS a call on 0115 9441036 or e-mail

Q. Can a drive replace a softstart?
A. Yes, softstarts are used for reduced torque starting and stopping of standard 3-phase induction motors (E.G. centrifugal pumps, compressors, ball mills, jar mills, fans/blowers and saws.) They are a popular alternative to DOL or ?Δ and always provide the correct torque for starting a motor and avoid the high starting currents seen by direct starting methods. However, once the motor is up to full speed the softstart is usually by-passed (to save energy). A VSD can replace a softstart for all applications and has the distinct advantage of all of the energy features described in these Q’s & A’s.

Q. Can I run my application at extremely low speeds?
A.The simple answer is yes; however, the answer needs further explanation and is slightly different for different types of load.

Applications such as centrifugal fans and pumps (the ones that are governed by Cube Law) are called variable torque loads. When they run at low speeds the motor’s normal cooling fan is perfectly capable of keeping the motor cool as at low speeds the motor uses very little power.

Applications such as conveyors, crushers, or mixers are generally called constant torque loads and still use considerable power even at slower speeds when under load. The motor is less efficient at lower speeds and can become very warm as the motor’s cooling fan is not able to dissipate the heat (it runs at the same speed as the motor). To overcome this problem motors for this type of application are often supplied with a separate motor controlling the cooling (sometimes called a forced vent motor) and allows the motor to keep cool even at lower speeds.

If you have an application that requires very low speeds, you might want to consider using a gearbox or geared speed reducer.

Q. What is the equation for converting Horse Power (HP) to kilowatts (kW)?
A. 1 HP = 0.746 kW and 1 kW = 1.34 HP.

Q. What is Cube Law?
A. Cube Law refers to relationship between power and speed at the shaft of the motor for variable torques application such as centrifugal fans and pumps. Please click here for more Cube Law information.

Q. Are variable frequency drives phase sensitive?
A. The input wiring is not sensitive to phase. If you changed one set of input leads, the rotation would not change. The output of the drive is sensitive to phase. Changing one set of leads to the motor changes the direction of rotation.

Q. How does a variable speed pump drive system save energy, compared to a system that runs with a normal contactor arrangement?
A. A pump drive system ran across-the-line will operate the motor at its base speed as the speed is determined by the fixed 50 Hz mains frequency. The flow will be controlled by mechanical restriction (valves, vanes, etc.); yet the motor will continue to consume close to the maximum required power. A variable speed pump drive system gives you the ability to adjust the flow by varying the speed of the motor. The torque load decreases as a function of the square of the speed (T = n^2) and likewise the power requirement decreases as a function of the cube of the speed (HP = n^3). This only applies to variable torque loads such as centrifugal loads such as pumps (without a static head) and fans. Click on the here for a practical demonstration.

Q. Can you service our inverters? Even if they are not ABB drives?
A. In short, yes. Please contact us on 0115 9441036 or email and we will arrange a survey and a subsequent bespoke service contract.

Q. Can you repair our Inverter(s)?
A. Yes, please contact or repair team on 0115 9441036 or email We also have the ability to arrange for a temporary hire drive if needed.

Inverter Drive Systems ( are the largest ABB AVP (Authorised Value Provider)  and have energy saving specialists available to perform free energy saving surveys call 0115 9441036 or email