What are the components of an electric motor?
Electric Motor Components Understanding the components of a motor and how it works can show how energy wastage can occur within a business. The diagram (below) shows the various parts that make up an induction motor, from the conduit box, where the electrical input is applied (either directly from the mains/grid supply or from a VSD), to the output shaft. Simply put, as electrical power is applied, a rotating magnetic field is created around the stator (1). This induces currents and associated magnetic fields in the rotor (2), causing the rotor and shaft (3) to spin. The shaft is mounted on bearings (4) and is able to rotate freely. When a motor is connected directly to an electrical supply it will accelerate to a fixed speed. However, when starting, the motor will draw a very high current as it accelerates. This is called the ‘motor starting current’. The starting current generates significant heat and it is for this reason that motor manufacturers normally state a maximum number of ‘starts’ per hour, as excess heat will considerably increase motor wear and reduce life expectancy. When a motor is connected to a soft starter or to a VSD, this starting current can be limited and a much smoother start can be achieved, resulting in less wear on the motor.
Why is the term Drive used in relation to electric motors?
The term drive is used to mean many things in industry, including being used as a generic word for motors, for drivetrains (such as gearboxes or pulley systems), and for controllers. More accurately, and for the purposes of this guide, ‘drive’ refers to a motor controller. A variable speed drive (VSD) is an electronic device that controls the electrical supply to a motor, enabling it to run at different speeds
What is Energy Efficiency?
Sustainable Energy Ireland Motor efficiencies vary, being influenced by the design of the motor and its life history. In the UK and Ireland, modern motors are typically supplied in three efficiency grades, high efficiency (EFF1), standard efficiency (EFF2) and lower efficiency (EFF3), with about 4% difference between each. Older motors may be several efficiency points lower than standard efficiency motors and motors that have been rewound are also likely to have incurred a drop in efficiency. EFF1 motors are sometimes referred to as higher efficiency motors (HEMs). Enhanced Capital Allowance ABB EFF1 Motors qualify for 100 per cent first-year Enhanced Capital Allowances (ECA) UK, accelerated capital allowance Ireland, which allows the full cost of an investment in designated energy-saving plant and machinery to be written off against the taxable profits of the period in which the investment is made. The general rate of capital allowances for spending on plant and machinery is 20% a year on the reducing balance basis
What is a Variable Speed Drive?
A Variable Speed Drive (VSD) is a device that can control the speed of an electric motor. Most conventional motors run at full speed only, but a VSD-equipped unit means it can run at a variable rate. This allows the motor to drive a pump or fan at a speed appropriate to the requirements of the process.
What are the main methods of starting a motor?
The following is a short description of the most common starting methods for a three phase squirrel cage motor. Each method has its advantages and disadvantages:
- Direct On Line (DOL) starting
- Star Delta Starting
- Varial Speed Drive (VSD) Inverter
Main methods for starting an electric motor (1) Direct On Line (DOL) This is by far the most common starting method available on the market. The starting equipment consists of only a main contractor and thermal or electronic overload relay. The disadvantage with this method is that it gives the highest possible starting current. A normal value is between 6 to 7 times the rated motor current but values of up to 9 or 10 times the rated current exist. Besides the starting current there also exists a current peak that can rise up to 14 times the rated current since the motor is not energised from the the first moment when starting. The values are dependent on the design and size of the motor, but in general, a smaller motor gives higher values than a larger one. During a direct-on-line start, the starting torque is also very high, and is higher than necessary for most applications. The torque is the same as the force, and an unnecessary high force gives unnecessary high stresses on couplings and the driven application. Naturally, there are cases where this starting method works perfectly and in some cases also the only starting method that works.
Direct On Line (DOL) (2) Star delta starting This is a starting method that reduces the starting current and starting torque. The device normally consists of three contactors, an overload relay and a timer for setting the time in the star-position (starting position). The motor must be delta connected during a normal run, in order to be able to use this starting method. The received starting current is about 30 % of the starting current during direct on line start and the starting torque is reduced to about 25 % of the torque available at a D.O.L start. This starting method only works when the application is light loaded during the start. If the motor is too heavily loaded, there will not be enough torque to accelerate the motor up to speed before switching over to the delta position. When starting up pumps and fans for example, the load torque is low at the beginning of the start and increases with the square of the speed. When reaching approx. 80-85 % of the motor rated speed the load torque is equal to the motor torque and the acceleration ceases. To reach the rated speed, a switch over to delta position is necessary, and this will very often result in high transmission and current peaks. In some cases the current peak can reach a value that is even bigger than for a D.O.L start. Applications with a load torque higher than 50 % of the motor rated torque will not be able to start using the start-delta starter. Star Delta Starter
What is a Frequency Convertor?
The frequency converter is sometimes also called VSD (Variable Speed Drive), VFD (Variable Frequency Drive) or simply Drives, which is probably the most common name. The drive consists primarily of two parts, one which converts AC (50 or 60 Hz) to DC and the second part which converts the DC back to AC, but now with a variable frequency of 0-250 Hz. As the speed of the motor depends on the frequency this makes it possible to control the speed of the motor by changing the output frequency from the drive and this is a big advantage if there is a need for speed regulation during a continuous run. In many applications a drive is still only used for starting and stopping the motor, despite the fact that there is no need for speed regulation during a normal run. Of course this will create a need for much more expensive starting equipment than necessary. By controlling the frequency, the rated motor torque is available at a low speed and the starting current is low, between 0.5 and 1.0 times the rated motor current, maximum 1.5 x In. Another available feature is softstop, which is very useful, for example when stopping pumps where the problem is water hammering in the pipe systems at direct stop. The softstop function is also useful when stopping conveyor belts from transporting fragile material that can be damaged when the belts stop too quickly. It is very common to install a filter together with the drive in order to reduce the levels of emission and harmonics generated
What is a Soft starter?
A softstarter has different characteristics to the other starting methods. It has thyristors in the main circuit, and the motor voltage is regulated with a printed circuit board. The soft starter makes use of the fact that when the motor voltage is low during start, the starting current and starting torque is also low. During the first part of the start the voltage to the motor is so low that it is only able to adjust the play between the gear wheels or stretching driving belts or chains etc. In other words, eliminating unnecessary jerks during the start. Gradually, the voltage and the torque increase so that the machinery starts to accelerate. One of the benefits with this starting method is the possibility to adjust the torque to the exact need, whether the application is loaded or not. In principle the full starting torque is available, but with the big difference that the starting procedure is much more forgiving to the driven machinery, with lower maintenance costs as a result. Another feature of the soft starter is the soft stop function, which is very useful when stopping pumps where the problem is water hammering in the pipe system at direct stop as for star-delta starter and direct-on-line starter. The soft stop function can also be used when stopping conveyor belts to prevent material from damage when the belts stop too quickly
Are manufacturers allowed to produce IE1 motors after 16 June 2011?
Standard efficiency (IE1) motors may no longer be placed on the European market as of 16 June 2011. As of that date all new motors will have to meet the IE2 (high efficiency) rating in Europe. EU MEPS does not apply outside Europe. Manufacturers can continue to supply IE1 non-CE marked motors to customers located in Europe for further shipment to non-European markets. In this case a statement is required from the customer confirming that the motors’ final destination is outside Europe.
When I purchase a motor, how can I be sure that it meets the requirements of EU MEPS?
Check the motor rating plate and ask for the test report. The rating plate should be stamped with the efficiency class – IE2 as a minimum – and efficiency values (see Markings and documentation). The IE class stamped on the plate must be based on the lowest efficiency value at the rated voltage/frequency/output combination shown on the rating plate. In the case of ABB motors, the IE class and efficiency values are stamped on the rating plate and test reports are available on ABB’s website.The efficiency class stamped on the rating plate is verified using the testing methods specified in IEC 60034-2-1: 2007. ABB utilizes low uncertainty testing methods.
Does EU MEPS cover motors for explosive atmospheres?
No, EU MEPS does not cover all the types of motor covered by IEC 60034-30. Some motors (such as motors for explosive atmospheres) are included in IEC 60034-30 but excluded from EU MEPS. As a global player, ABB will follow the requirements of IEC/EN 60034-30. Even though it is not required under EU MEPS, ABB will also provide IE markings for standard motors for explosive atmospheres.
Does EU MEPS cover marine motors?
No. Marine motors are designed for ambient temperatures outside the range -15°C…+40°C, specified in the Comission Regulation EC 640/2009.
Does EU MEPS cover brake motors?
No. Brake motors are excluded from the Comission Regulation EC 640/2009.
If a motor is rated for altitudes in excess of 1000 m does it fall within the scope of EU MEPS?
Yes, if the motor is of a standard type but de-rated for operation at altitudes in excess of 1000 m. No, if the motor has a special design (winding, fan, grease, etc.) for operation in excess of 1000 m.
Can a motor without IE marking be placed on the European market after 16 June 2011?
No. Motors placed on the market on 16 June 2011 or after must have the IE marking. Even if the motor was ordered before 16 June 2011 it cannot be delivered without the IE marking after 16 June 2011. ABB will roll out the new IE rated motors into all central stocks in time for the introduction of EU MEPS.
Can a motor be rewound and still be used after 16 June 2011?
EU MEPS does not regulate rewinding. As long as the motor has been placed on the market or put into service prior to 16 June 2011 it does not have to meet the minimum efficiency requirements. This means that when a motor fails the user has the normal choice between rewinding and replacement. Even though rewinding is still permitted, however, the user should carefully consider the advantages of replacing the motor rather than having it rewound. Each rewind normally reduces a motor’s efficiency by 1 – 3%. In many cases the payback period for a new motor is less than three years. A new high efficiency motor costs less over the long term, because the initial purchase cost is much lower than the lifetime operating expenses.
What does EU MEPS mean by ‘placed on the market or put into service?
The way these concepts should be understood is that ‘placing on the market’ (making a product available for the first time on the EU market) and ‘putting into service’ (first ABB LV Motors | EU MEPS for low voltage electric motors use of a product for its intended purpose by an end-user in the EU) refer to two different ‘moments’ in the process of bringing a product to the market. Compliance for entry into the market is required only once, based on the moment when the product is placed on the market or when it is put into service. Accordingly, Article 3 of the Ecodesign Directive (2009/125/EC) should be taken to mean that products covered by implementing measures may be placed on the market or put into service, or both, only if they comply with those implementing measures and bear CE marking in accordance with Article 5.A product has to comply with the requirements for CE marking from the moment that it is placed on the market. Only in cases where a product is not placed on the market in the literal sense shall the moment of compliance be the time when the product is put into service.As of 16 June 2011 motor manufacturers cannot ‘place on the market’ (sell) motors in Europe that are destined for final use in the EU market and do not meet IE2 efficiency levels. Motor users cannot ‘put into service’ (install) new motors that do not have the correct IE2/CE marking. However, users can install motors from their stock that were purchased before 16 June 2011.
As of 16 June 2011, are distributors or OEMs allowed to sell IE1 motors put into their stock previous to that date?
Yes, the EU legislation is not retroactive. These motors can be sold provided that they were put into stock or into the distribution chain before 16 June 2011. Products legally placed on the market can stay on the market and still be sold to the end-user and put into service.
Does EU MEPS apply to ‘dual purpose’ smoke extraction motors?
The answer depends on the type of motor:
– Yes, if the motor can be tested by the motor manufacturer at rated power and normal ambient with its own fan. This type of motor is covered by EU MEPS and must have the correct IE markings as of 16 June 2011.
– No, if the motor cannot be tested independently at rated power (ie, it requires a fan supplied by an outside manufacturer). These products – known as TEAO or Totally Enclosed, Air Over motors – are not covered by EU MEPS.
Does EU MEPS cover motors intended for VSD use?
Motors that can be used with a VSD and run direct on line (DOL) are covered by EU MEPS and must have the correct IE marking. Motors produced for VSD duty only (motors that cannot be run DOL), such as permanent magnet motors, are not covered and do not need an IE marking.