Hertz Kompressoren UK has launched its new HSC-D direct drive, variable speed rotary screw compressors, covering kW outputs from 22kW to 315kW, Because the motor shaft directly drives the compressor unit without the need for additional parts, such as belts, the compressors offer a particularly compact design. The direct drive transmission system also affords impressively quiet operation at a lesser dB level at peak load compared to belt diven models. A further benefit of the direct driven system is that vibration levels are considerable decreased, contributing to reduced wear & tear, greater longevity and a longer timeline between routine maintenance and service schedules.
Energy efficient properties
Furthermore, due to the direct drive compressors’ ability to generate more pressurised air with less energy, there are also convincing cost-saving and environmental benefits to be had. Additional energy efficiency properties are provided courtesy of the compressors’ frequency inverter, which accurately adjust the motor speed in accordance with the required air demand of the user. Energy consumption keeps decreasing almost linearly in proportion with the capacity, reducing energy consumption by as much as 35 per cent. Also, the wide capacity ranges allow the HSC-D compressors to supply the required amount of pressure continuously and at a constant level. With these benefits, not only are additional energy savings made possible, but the potential for unfavourable pressure change effects on some critical equipment are also prevented. Another contributing factor regarding the compressors’ energy efficiency properties is their IE2 efficiency electric motors. All compressors within the HSC-D range are fitted with electric motors that meet IE2 efficiency class (motors that meet IE3 effiency class are optional). The motor safety factor has been increased to 1,2 – 1,4 with larger motors. They also offer increased radial force resistance due to a special bearing, shaft and lubrication design.
Benefit of VSDs
The HSC-D compressors’ electric motors offer high efficiency even at low speeds due to the inclusion of high-efficiency Variable Speed Drives (VSDs). Analogue outputs are included for a secondary VSD drive for fans. Additionally, the compressors include master/slave functions and a new mod-bus protocol for VSD Communication. Frequency controllers of these VSD compressors are high-quality drives featuring one brand and one Model VLT for the whole compressor series. They are very user-friendly with an easy-to-follow menu structure, and the controllers are also easy to install, with no need for any setup on the VSD drive. An additional benefit is that of the strong worldwide after-sales service.
With the VSD for the fan, a constant temperature is achievable, potentially resulting in major energy savings. The heat regime is fixed by controlling the fan revolution speed according to the airend temperature with a secondary drive. Constantly running at the airend’s most efficient temperature is achieved, resulting in energy savings on the main motor. This also results in little or no temperature fluctuations, which extends the life of all components within the Frecon compressor. Another benefits include: highly efficient cooling and extra energy saving on the fan; reduced noise levels due to the lower running speed of the fan; and extended fan life due to less mechanical stress as a result of no on/off fan operation.
The compressors are also fitted with controllers for improved functionality, reliability and a number of new functions; these include the ability to record used total energy levels. HSC-D models also feature a PID activation timer to prevent the airend from speed up without sufficient lubrication, and a PID activation temperature parameter to prevent the airend from cold speed-up.
Benefits of Soft Start
The new range of direct drive compressors also features state-of-the-art Soft Starters, as an alternative to the more traditional star delta starting method. The Soft Start system can extend the motor’s service life and avoid high start current on the energy system. With this system the motor can start as many times as required, while short idle time periods can result in additional energy savings. Additionally, the Soft Start system can minimise starting currents, eliminate current spikes and reduce voltage drops on the network. Furthermore, the system can optimise cabling and minimise inrush current with no transition spikes. In term of mechanical benefits afforded by the Soft Start system, these include: minimised stress on transmissions such as gearboxes, couplings and bearings on motor/airend; substantially reduced maintenance costs; and reduced downtime. These advantages can result in up to 35 per cent of a HSC-D Series compressor’s total cost being saved after a five-year application period.
Airends with new rotor profile and lobe combination
The high-efficiency airends used on the HSC-D Series are supplied by the world’s leading airend manufacturers. They are designed based on a new rotor profile and lobe combination, which is the result of long experience of screw compressor performance, new CAD methods and utilisition of modern production technology. In Hertz series airends the male rotor has four lobes and the female five lobes. This ensures the shortest seal line and smallest inner leakage, and also provides more air volume capacity. The new rotor profile with minimised ‘blow hole’ reduces torque requirement, resulting in low pressure consumption.
Cold start option
In Winter time and in cold environments compressor oil has a higher viscosity and therefore cannot produce adequate levels of lubrication during start up. Because of this, screws can wear and fail easily. To overcome this situation the HSC-D Series air compressors include heating cartridges assembled in a separator tank to warm up the oil. This keeps the oil at a temparature that makes start ups during cold periods effective, without any failure or risk of damage to the screws. The cold start option is available for all models within the Series.
Efficient cooling system
The HSC-D Series includes an efficient direct-driven cooling system to ensure the compressors run at a continuous optimum temperature. A ‘Plate/Bar’-type aluminium oil/air combi-cooler is fitted as standard to all models within the series, and promotes extended compressor life. The cooler’s size has been selected to provide trouble free operations even in high ambient temperatures. Additionally, the near-silent axial fans feature new highly efficient blade profiles, while the fan’s housing has been designed to make the servicing and cleaning of the coolers as simple as possible. A water-cooling option with ‘Plate/Bar’- type copper heat exchangers is also available.
The HSC-D Series’ electrical system is in compliance with the Low Voltage (73/23/EEC) Directive, the EMC filter is in complience with the EMC (Electro Magnetic Compatibility) 89/336/EEC Directive, and the compressors’ harmonic filter in complience with IEC/EN 61000-3-12 norms at all power rates.
A full five-year warranty is offered as standard on major parts; including the airend, main drive motor, oil/air cooler and oil reclaimer. A standard 12-month warranty is available on all other equipment provided certain conditions are met.