10 things to consider when choosing an electric motor
Electric motors are critical components in the engineering industry. Various designs are suited for different classes within the domain. Thus, selecting the right electric motor is a tedious but critical process. The motor you choose is based on the conditions in which it will function and the load it will handle.
Factors to Consider While Choosing Electric Motors
Electric motor manufacturers in India consider several criteria and factors while creating different types of motors. Engineers must consider each of these factors when choosing an electric motor too. These are:
- Nature of electric supply
- Types of drives
- Types of loads
- Gear drive
While these are the primary factors to be considered, several other factors also contribute to maximising the utility of the motor you choose. One of the most important factors to consider is the overall cost. While it is the last factor on the list, it is the most influential factor as budgets ultimately determine what enterprise funds are spent on. Any electric motor you choose combines functionality, expense and availability.
1. Nature of Electric Supply:
Electric supply types available are single-phase AC, 3-phase AC and DC. Single-phase electric motors are generally used for small loads since their outputs are limited. When 3-phase AC is available, engineers can use polyphase induction motors, slip-ring type motors and squirrel cage types as long as they suit the load requirement. In situations where it’s not convenient to use speed variation, stepped-pulley or pole-changing motors prove effective alternatives.
2. Type of Drive:
There are three broad groups under which electric drives used today can be divided:
- Group drive: This refers to the drive where a single motor drives a line shaft, empowering entire groups of machines to be operated upon. It is also known as the line shaft drive.
- Multi-motor drive: This refers to several individual drives that operate one working mechanism within a production unit. Multi-motor drives are critical in complex paper-making machines, metal-cutting tools, rotary printing machines, rolling mills and other types of machines.
- Individual drive: This refers to the drive where a single motor drives an individual machine out of a range of available machines. While individual drives have a higher cost than group drives, every operator has complete control of their machine. They can alter the speed wherever necessary and even stop the machine when it is not in use. This eliminates any no-load losses.
3. Types of Loads:
Loads can be divided into two broad categories – those that ensure active torques and those that provide passive torques. Active torque is a result of either gravitational force (including actions of lifts, elevators, hoists and operations of locomotives on a gradient) or deformation in elastic bodies. This type of torque also develops during the release or compression of springs. The functioning of mechanisms like hoisting, locomotive operations on gradients or the release or compression of springs is closely tied to changes in the drive’s potential energy. As a result, active torques are connected closely to potential energy.
4. Gear Drive:
Gear drive is a short-centre positive drive. Engineers must ensure proper gear drive alignment, as failure to do so might result in delays and costs due to bent motor shafts. This was the earliest known power transmission technique in the first steam mills. Modern gears, the straight cut ones and the unique variation observed in worm-reduction drives are common in cloth calendars and other heavy machines. An average 35kW worm gear with a 15:1 speed reduction will provide about 98% of mechanical efficiency.
An aesthetically appealing physical design is fundamental to utility. This can be achieved by blending the mounting, dimensions and motor finish harmoniously to align with the driven machines.
As mentioned before, costing is one of the most influential factors when choosing a suitable electric motor. It is placed last in this list since it is one of the most obvious and common factors. However, you cannot have a conversation about a fundamental engineering tool or element without talking about costs and budgets. Sometimes, enterprises opt for sub-optimal products and electric motors because they are the best option within their budget. Often flashy, additional features cost more without adding significant value to the manufacturer.
While initial and setup costs are vital, also consider the running cost, which includes maintenance costs, losses, depreciation and interest. In several cases, using poor-quality motors could save on initial investments but incur additional charges because of poor efficiency, shorter lifecycle and lower power. This could prove more expensive than a single expensive motor that helps increase efficiency. Therefore, cost consideration means choosing the product with the desired efficiency at the lowest possible cost.
Trusted partners like Godrej provide customised electric motor solutions for manufacturing and designing a broad spectrum of motors for manufacturers and calibration labs in India. Contact these experts for manufacturing requirements you might have.