5 Most Common Motor Load Types

5 Most Common Motor Load Types

Load profile (speed range, torque and power)

Certain load types are characteristic in the industrial world. Knowing the load profile (speed range, torque and power) is essential when selecting a suitable motor and frequency converter for the application.
Some common load types are shown. There may also be combinations of these types.

1. Constant Torque
2. Quadratic torque
3. Constant power
4. Constant power/torque
5. Starting/breakaway torque demand

1. Constant torque

A constant torque load type is typical when fixed volumes are being handled. For example screw compressors, feeders and conveyors are typical constant torque applications.
Torque is constant and the power is linearly proportional to the speed.

Figure 1 – Typical torque and power curves in a constant torque application

2. Quadratic torque

Quadratic torque is the most common load type. Typical applications are centrifugal pumps and fans. The torque is quadratically, and the power is cubically proportional to the speed.

Figure 2 – Typical torque and power curves in a quadratic torque application

3. Constant power

A constant power load is normal when material is being rolled and the diameter changes during rolling. The power is constant and the torque is inversely proportional to the speed.

Figure 3 – Typical torque and power curves in a constant power application

4. Constant power/torque

This load type is common in the paper industry. It is a combination of constant power and constant torque load types. This load type is often a consequence of dimensioning the system according to the need for certain power at high speed.

Figure 4 – Typical torque and power curves in a constant power/torque application

5. Starting/breakaway torque demand

In some applications high torque at low frequencies is needed. This has to be considered in dimensioning. Typical applications for this load type are for example extruders and screw pumps.

Figure 5 – Typical torque curve in an application where starting torque is needed

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Variable Frequency Drive Cable Construction: ÖLFLEX®VFD 2XL

Cable basics: Understanding Dynamic Load-Bearing Capacity

Choosing the best cable for an industrial application is one of the most critical design decisions of any complex automated system. That said, cable selection is often an afterthought and not given the
cable.
time or respect it deserves. As the lifeblood of the system, cables and wires are vital to transmitting power and sending control signals and data across wide expanses in a timely and reliable manner. Here we take a look at some of the most important factors to consider when specifying industrial

Wires and cables intended for use within cable tracks are subject to enormous loads. Especially in highly dynamic applications, several factors should be considered when choosing the right cable—durability, reduced weight, a small minimum bending radius and the ability to fit within tight spaces.
Many of today’s automated production environments must meet rigorous productivity benchmarks, often requiring components to handle speeds of 5 m/s and acceleration of 50 m/s2, along very lengthy paths. To meet these demands, every component in the system must be optimized to work together,
including the cable, wiring, cable tracks and carriers.

Knowing the specific application and industrial setting in which the cable track will be used will help determine the characteristics required in its interior parts—the cables and wires. A good place to start is understanding the physical forces acting on the system. Regarding mechanics, the following loads
must be considered:

PUSH AND PULL LOADS. These forces act in the longitudinal direction of the wire.

• Static—Vertical forces such as gravity act on stationary cables (ex. fountain submersible pumps).
• Dynamic—Horizontal forces from acceleration/ deceleration act on the wires within the cable track.
• Static and dynamic—Cables moving vertically in cable tracks are subjected to both gravity and acceleration/ deceleration, for example in an elevator.

BENDING LOADS. Three distinct bending methods include the following.


• Simple flexing (tick/tock)—Flexing at a single, defined break point.
• Continuous flexing—Flexing that occurs along the entire cable length.
• Guided flexing—Continuous flexing using a guiding component. (ex. pulleys)


Cables used in tracks are exposed to bending along their entire length and are therefore subjected to continuous flexing. When specifying components for this type of use, it is important to choose cable specifically designed to handle these forces. For example, ÖLFLEX® FD and ÖLFLEX® CHAIN power and control cables from Lapp are carefully engineered for this purpose.

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