Are you in the market for a new air compressor? If so, you may be considering a fixed-speed compressor as an option. But before you make your purchase, you need to understand the limitations and drawbacks of fixed-speed compressors.
In this article, we outline 6 reasons why you may want to consider an alternative. Read on to learn why a fixed-speed compressor may not be the right choice for your plant.
What is a fixed-speed air compressor?
A fixed-speed air compressor operates at a constant speed, regardless of air demand or pressure. This means that the compressor's motor runs at a set RPM, and the air pressure and flow rate remain constant. These types of compressors are generally less expensive than variable-speed compressors but they are also less efficient.
1. Power consumption
The main reason to avoid a fixed-speed rotary screw compressor is its excessive power consumption. Fixed-speed compressors operate continuously, drawing maximum electricity to maintain a top speed, or RPM. This makes them extremely inefficient, particularly during periods of intermittent air usage. Instead of slowing down or switching off to match air usage, a fixed-speed compressor runs at full speed all the time, releasing excess compressed air through a bleed valve.
2. Frequent maintenance
The constant high-speed operation of a fixed-speed compressor results in increased wear and tear on its moving parts. Components like the motor, bearings, gearing and air end are subject to excessive friction over time, leading to longevity issues and malfunctions. Over time this means a lot of plant downtime and is a maintenance expense you could do without.
3. Efficiency
Fixed-speed compressors are often manufactured with smaller air ends to make them more affordable. To achieve the desired free air delivery, a pulley or gearing system is used which can reduce the lifespan of the air end component. For example, when the motor is running at 3000 RPM, the air end may be operating at 6000-7000 RPM, putting the part under excessive stress.
On the other hand, variable-speed compressors use direct drive motors that adjust the speed to meet air demands. Additionally, the use of permanent magnet motors in variable-speed drive machines can result in even greater energy savings because they require up to 40% less energy to perform the same work as traditional electric motors. In fact, permanent magnet motors have been a key factor in the success of companies like Tesla.
4. Current spikes
When you turn them on and off, fixed-speed compressors consume a large amount of electricity. They reach full speed instantly, resulting in a large surge in electricity usage. This can result in issues with the power supply for the rest of your plant and equipment. However, with a variable-speed compressor, a 'soft-start' will gradually activate the motor and increase its speed over a period of 10-15 seconds, avoiding any sudden spike in electricity usage.
5. Stops and starts
When air consumption has stopped for an extended period, a fixed-speed compressor will automatically shut down. When the pressure in the tank drops again, it will start back up again. This puts a lot of strain on the motor and moving parts, meaning more repairs and even replacements. With variable-speed compressors, the soft-start feature allows for an unlimited number of starts and stops without putting undue stress on the motor.
6. Future growth
Unfortunately, fixed-speed compressors have to be matched according to your current air demand, with no consideration for the future. That’s because they should be running consistently to make the most of limited starts and stops. This requires compressed air to be used at a consistent rate, matching the compressor's output to prevent it from shutting off during periods of low air usage.
As your plant and business grow, this means you will need to purchase additional equipment or replace the current machine to match your usage – even if the compressor is relatively new. With a variable-speed compressor, you can safely opt for an oversized model as it can run at as low as 25% of its capacity for extended periods. When your air consumption changes, it can be easily adjusted to match.
In conclusion
While fixed-speed compressors are commonly used, many plants and workplaces would be better off looking at an alternative. Fixed-speed compressors can be:
- Inefficient
- High maintenance
- Costly
- And prone to frequent stops and starts.
What’s more, your plant will likely need to invest in another compressor as soon as your air requirements change. For a better long-term investment and lower running costs, a variable-speed compressor will be a wiser choice.
View the Industrial Air Systems range of variable-speed compressors here >>
What are variable-speed air compressors?
As the name suggests, variable-speed air compressors can be adjusted based on air demand or pressure. This means the motor can change its RPM, and the air pressure and flow rate will also change accordingly.
These compressors are generally more expensive up-front than fixed-speed compressors, but they are more energy-efficient, have longer lifespans, and offer better performance. They match the air demand, reducing the amount of energy wasted by running at a constant high speed.
Permanent magnet air compressors
A permanent magnet air compressor is a type of variable speed compressor with permanent magnets to help the motor work more efficiently. It can change its speed depending on the air demand and will produce more torque at lower speeds which is better for maintaining a steady flow and pressure. It also operates at lower noise levels compared to traditional compressors.
Investing in a permanent magnet compressor can save you money in the long run and ensure that your compressed air system is always operating at the optimal level. These compressors have several benefits, such as:
- Energy efficiency
- Low maintenance
- Unlimited starts and stops
- Capacity for changing air demands
- Longer lifespan
- Lower noise levels.
If you're looking to upgrade your air compressor, see our variable-speed compressors and our permanent magnet air compressor range. Whatever your needs, we have a compressed air solution to suit you.
Contact us today to learn more about our products and how we can help you improve your plant’s operations. Or take a look at our latest brochure.
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