Efficiency Losses in an IE4 Motor: Where Do Iron, Copper and Friction Losses Decrease?

When buying an IE4 super premium motor, the high efficiency value you see on the nameplate is actually the result of a battle against losses taking place inside the motor. Every electric motor cannot convert a portion of the energy it draws from the grid into mechanical power; this energy is lost as heat. The reason an IE4 motor is more efficient than an IE3 is that it is designed to reduce these losses one by one. As a buyer, understanding where these losses occur and how IE4 reduces them lets you see concretely why you are investing in a higher efficiency class. In this article, as HEM Motor, with our identity as both manufacturer and supplier, we address the efficiency losses inside an IE4 motor under the headings of iron, copper, friction and load losses, and we show how this knowledge reflects on your purchasing decision.

Where Do Efficiency Losses Occur in a Motor?

In an asynchronous motor, total losses are gathered into four main groups: iron (core) losses, copper (winding) losses, mechanical losses (friction and windage), and load losses (additional/stray losses). The sum of these four items determines how much of the power the motor draws is converted into heat, and therefore its efficiency. The IE4 super premium class reduces total losses by improving each of these four items. We addressed at which powers the efficiency classes apply in terms of legal requirement in our article on the IE3 and IE4 efficiency requirement; here we examine where this efficiency technically comes from.

Efficiency is usually stated on the motor nameplate as a percentage or as an IE class. Correctly reading the efficiency value and other rated values on the nameplate is the basis for realistically comparing two motors. We explained nameplate reading from a purchasing perspective in our article on reading the IE3 motor nameplate: kW, speed, cosφ and efficiency; the same discipline applies to IE4 motors.

Iron (Core) Losses: Steel Quality and Thinness

Iron losses occur in the motor's magnetic core (stator and rotor laminations) and have two components: hysteresis loss and eddy current loss. The magnetic field changing direction hundreds of times per second creates a continuous magnetic cycle and unwanted eddy currents inside the steel; these turn into heat. The way to reduce iron loss in IE4 motors is to use lower-loss (high-quality silicon) electrical steel and to pack the laminations in thinner sheets insulated from one another. Thin, quality steel reduces loss by shortening the eddy current paths. Iron loss is almost constant as long as the motor is energized; that is, it occurs even when the motor runs at no load. Therefore, even a small improvement in iron loss creates a noticeable difference in annual consumption for motors that run many hours.

Copper (Winding) Losses: I²R Loss and Winding Cross-Section

Copper losses occur when the current flowing through the winding turns into heat in the winding's resistance; in physics this is called the I²R loss. Because it increases with the square of the current, copper loss grows rapidly as the load increases; therefore, copper loss is the loss item most sensitive to load. The primary way to reduce this loss in IE4 motors is to lower the winding resistance. For this, more and higher-quality conductor is used; the slot fill ratio is increased and 100% copper winding is preferred. Since copper has a lower resistivity than aluminum, it produces less heat at the same current. We addressed this difference between copper and aluminum winding in detail in our article on the difference between copper and aluminum winding in motors; the high efficiency of IE4 largely rests on this improvement on the winding side.

All IE4 motors in the HEM Motor range are produced with 100% copper winding. This both reduces copper loss and, by allowing the motor to operate at a lower temperature, extends insulation life. You can examine the effect of low operating temperature on lifespan in our article on winding and insulation class (F/H) in IE3 motors; efficiency and lifespan are two gains that feed each other on the winding side.

Friction and Windage Losses: Bearing and Fan Design

Mechanical losses come from two sources: bearing friction and the power the cooling fan spends to move air (windage loss). These occur as long as the motor rotates and increase with speed. To reduce this loss in IE4 motors, low-friction quality bearings, optimized lubrication and aerodynamically improved fan design are used. There is an interesting balance: the fan is necessary to cool the motor; however, an oversized fan creates unnecessary windage loss. The IE4 design optimizes this balance between cooling and windage loss. We addressed the effect of fan and cooling design on efficiency in detail in our article on the effect of cooling and fan design on efficiency in IE4 motors.

The same design improvements also contribute to the motor running more quietly and with lower vibration, because a well-balanced rotor and an optimized fan reduce both loss and noise. You can examine the reflection of quiet and low-vibration operation in IE4 motors in our article on quiet and low-vibration operation in IE4 super premium motors.

Load (Stray) Losses: Design and Workmanship

Load losses (also known as stray or additional losses) are the item consisting of irregularities in the magnetic flux distribution and high-frequency losses outside the three main items above. Although they appear relatively small, load losses directly reflect the motor's design quality and workmanship. In IE4 motors, optimizing the slot geometry, keeping the air gap precise and quality manufacturing reduce these losses. Load loss grows as the load increases; therefore, reducing this item provides a significant gain in heavy-duty applications.

Considering the four loss items together explains why an IE4 motor is more expensive but more economical in the long run: IE4, with the sum of the small improvements it makes in each loss item, offers lower electricity consumption for years. You can examine the real consumption calculation and payback period of replacing an old motor with an IE4 in our article on what replacing your old motor with an IE4 gains; and how to decide between IE4 and IE3 in our article on staying with IE3 or moving to IE4.

Losses and Efficiency: The Importance of the Load Point

A motor's efficiency depends not only on its design but also on the load point at which it operates. The efficiency curve peaks between about three-quarters of the rated load and full load; efficiency drops at very low load or at overload. The reason is the structure of the losses: because iron loss remains constant independent of load, at low load this constant loss holds a large share within the total; at very high load, copper loss (I²R) grows rapidly and pulls efficiency down. Therefore, actually capturing the high efficiency of an IE4 motor on site is possible by running the motor at the correct load point.

This knowledge directly affects the purchasing decision. An oversized motor runs continuously at low load and moves away from the peak of the efficiency curve; that is, you cannot fully use the efficiency of the extra IE4 investment you paid for. An undersized motor, on the other hand, runs continuously with high copper loss, so both its efficiency drops and the risk of early failure increases. Correct sizing is a precondition for carrying the IE4 motor's efficiency advantage to the field. We addressed the mistakes made in motor sizing in our article on the 7 most common mistakes when buying an electric motor.

How Do Losses Differ Between IE4 and IE5?

As the efficiency class rises, reducing each loss item becomes increasingly difficult, because the easy gains were obtained in the lower classes. IE5 ultra premium motors, often with synchronous reluctance technology, lower especially the rotor-side losses even below those of IE4; however, these motors usually run with a drive. We addressed whether the efficiency difference between IE4 and IE5 justifies the investment in our article IE5 or IE4? Does the efficiency difference justify the investment?. For most general-purpose industrial applications, IE4 super premium is a balanced choice that reduces losses sufficiently and can run direct-on-line without requiring a drive.

This comparison helps the buyer clearly determine which efficiency class to invest in. The highest class may not be the right choice for every application; what matters is selecting the class compatible with the application's operating hours, load profile and payback expectation. By making this evaluation together, we can identify the motor that reduces losses at the most appropriate cost.

How Does Reducing Losses Reflect on the Purchasing Decision?

Understanding efficiency losses is not abstract engineering knowledge but a concrete purchasing advantage, because each loss item reflects directly on the electricity bill and the motor's operating temperature. A low-loss motor both consumes less energy and lasts longer by heating up less. We addressed in which application migrating to IE4 is a priority in our article on which plant should migrate to IE4 super premium first; and the IE4 threshold in pumps, fans and compressors in our article on the IE4 threshold in pumps, fans and compressors. The IE4 motor and efficient electric motors in the HEM Motor range, with their design optimized across these four loss items, gain the buyer both energy and lifespan.

You can access our entire product range and corporate information from our home page. Selecting the right efficiency class is a strategic decision that lowers the motor's total cost of ownership over the years.

Frequently Asked Questions

Which loss decreases the most in an IE4 motor?

The IE4 super premium design improves each of the four loss items; however, the most noticeable gain is often achieved in copper (winding) and iron (core) losses. More and higher-quality copper conductor lowers the winding resistance, while lower-loss and thinner silicon steel lowers the core loss. Improvements in friction and load losses also contribute to total efficiency. The combined effect of these items allows the IE4 motor to consume less energy than an IE3.

What is the difference between iron loss and copper loss?

Iron (core) loss is almost constant as long as the motor is energized and occurs independently of load; it is present even when the motor runs at no load. Copper (winding) loss, on the other hand, is very sensitive to load because it increases with the square of the current; it grows rapidly as the load increases. Therefore, both items matter in applications that run many hours but with variable load. The IE4 motor is designed to reduce both at once, so efficiency stays high both at no load and under load.

How does the reduction in efficiency loss reflect on my electricity bill?

Each loss item means that a portion of the power the motor draws turns into heat, that is, is wasted. The low losses of an IE4 motor mean it does the same work with less electricity; this difference turns into a noticeable saving in annual consumption as the motor runs more hours. The real saving amount depends on the motor's power, operating hours and load profile; if you share the details of your application, we can evaluate the payback period together.

Get a Quote

Contact the HEM Motor expert team for our IE4 super premium motors with optimized iron, copper and friction losses, 100% copper winding and class F insulation. We quote the high-efficiency motor in the right power and speed for your application, together with stock and delivery time information. Call us now at +90 (532) 345 49 86 or request a quote via our contact page.