The drivetrain in our Rollair V range of compressors is an incredible feat of engineering. A drivetrain consists of 3 key parts, and we made improvements on every one of them. It features an oil-cooled interior permanent magnet motor, an integrated direct drive transmission, and our new screw element. These three innovations have a major impact on the compressor's overall efficiency, reliability, and productivity. Let's take a closer look at how they are improved.
• In-house designed iPM motor (1) with IE4 Super Premium Efficiency
• New generation in-house designed screw elements (2) with improved efficiency
• Integrated direct drive transmission (3) for minimal losses
• Smart inlet valve (5) optimizes the inlet flow and improves efficiency
• iPM motor (1) rated IP66, protected against dust and water ingress
• Globally renowned screw elements (2), proven in thousands of installations
• Optimal cooling at all speeds and conditions thanks to the oil-cooling principle (4) of the iPM motor (1)
• No greasing of the motor (1) bearing needed
• Coupling-free direct drive design (3), no maintenance needed
• Smart inlet valve (5), no maintenance needed
The first big impact on the Rollair V's efficiency comes from our in-house designed iPM motor which is rated at IE4 Super Premium Efficiency according to IEC 60034-30, a standard on efficiency classes for low voltage AC motors. Compared to conventional induction motors, our iPM motor benefits from significant energy savings thanks to lower heat losses and by completely avoiding slip losses. In terms of protection, the motor itself is IP66 rated (protected against dust and multi-directional, high-pressure water jets).
In a conventional induction motor, an electric current flowing in the stator windings in a rotating motion will, thanks to electromagnetism, create a rotating magnetic field (RMF) in the stator. The RMF rotates at synchronous speed. Through electromagnetic induction, the RMF also induces an electric current and a magnetic field in the rotor. This magnetic field in the rotor will try to catch up to with the RMF of the stator but will always be behind in speed. In other words, the rotor rotates at asynchronous speed. The differences between synchronous and asynchronous speed are called slip losses and reduce the efficiency of the motor. Because current is induced in the rotor to create the rotor's magnetic field, the heat losses are rather high which further reduces the efficiency of the motor.
In our iPM motor, permanent magnets are housed inside the rotor. When the electric current is flowing in the stator windings they create a rotating magnetic field (RMF). As a result, the permanent magnets inside of the rotor will be attracted by, and start rotating with the RMF of the stator. The rotor will rotate at the same exact speed as the RMF of the stator at synchronous speed, meaning there are no slip losses. The heat losses are also lower than those in conventional induction motors since no current needs to be induced in the rotor (the magnetic field of the rotor is created by the permanent magnets inside of the rotor).
Another innovation is our new and latest generation of screw elements. Our globally renowned screw elements are designed and produced in-house in Belgium. By improving the rotor profile and reducing the pressure losses and leakages we were able to increase Free Air Delivery (FAD) while at the same time reducing the Specific Energy Requirement (SER) which means that we can deliver more compressed air while consuming less energy.
The third improvement comes in the form of an integrated direct drive transmission, which means that the motor and screw element rotate together as one functional unit, resulting in zero transmission losses. Unlike conventional direct drive transmissions, this design is coupling-free, keeping transmission losses and service costs to a minimum.
Unlike a conventional air-cooled induction motor, our iPM motor is oil-cooled which assures optimal cooling at all speeds and conditions, increasing the reliability and motor lifetime. Oil is injected in the motor housing and runs through canals around the motor, cooling it evenly. The oil then continues to the screw element where it lubricates and cools the rotors. This process is repeated over and over. If the oil gets too hot, it runs through the oil-cooler first before returning back to the motor.
The benefits of the oil-cooling principle are clear, especially at lower motor speeds/loads. When variable speed compressors regulate the motor speed to match the air supply to the air demand, two things happen in a conventional induction motor: Firstly, the motor generates more losses as the efficiency of the motor drops resulting in higher motor temperatures. Secondly, the speed of the motor cooling fan is reduced which reduces cooling capacity and further increases motor temperature. Higher motor temperatures reduce motor lifetime and can, in the worst case, result in a total failure of the motor.
However, our oil-cooled iPM motor acts differently when operating at lower speeds/loads. It generates fewer losses as the iPM motor technology is able to maintain its' high efficiency even at lower speeds/loads. Secondly, as the cooling is independent of a motor cooling fan, optimal cooling is assured even at low speeds/loads. Overall, this results in lower motor temperatures at all speeds and conditions, which extends motor lifetime and reliability.