The advantages of speed control

According to the results of an EU survey each year in the European Union some 80 TWh (80 x Wh) of power is consumed in compressed air plants. This is equivalent to over 10% of the industrial power requirements of the EU. According to the results of an EU survey each year in the European Union some 80 TWh (80 x Wh) of power is consumed in compressed air plants. This is equivalent to over 10% of the industrial power requirements of the EU. Basis: Power costs: 0.06 €/kWh, depreciation costs:: 5 years, interest: 5% Maintenance costs Investment costs Energy costs Average overall costs of a compressed air station?

The most important reasons for this are: The costs of energy for: 1.Expensive no-load times of compressors 2.Expensive pressure balance times of compressors 3.Compressed air lost during pressure balance processes 4.Very broad pressure bandwidths of compressors 5.Direct output losses during the production of compressed air (e.g. transmission losses owing to gears, V-belts) 6.Leaks in the compressed air network Potential savings from using speed-controlled compressors Important: A compressed air station should:  have as many load operating hours as possible  and, if possible, not a single no-load hour! Why are the energy costs constitute such a high proportion?

Investigations show that the max. delivery quantity is only required during peak times and that on average most compressors only utilise % of their capacity 4,000 operating hours p.a.; average full capacity utilisation 50-70% 20%40%60%80%100% Cumulative frequency % capacity utilisation Capacity utilisation with conventional compressors

exact output adjustment At 100% air requirement, conventional compressors and speed-controlled compressors work at full load. If the requirement drops, conventional compressors go into load-/no-load control. The drive motor performs switching cycles in which the pre-set coasting-down time has to be taken into account. The VARIABLE series varies its speed, hence reducing the delivery quantity exactly to match the requirements. Coasting-down time Compressed air requirement Time Conventional Load / no-load regulation Coasting-down time Speed control by means of SCD - technology 0 % 50 % 100 % 0 % 50 % 100 % 0 % 50 % 100 % No-load times Coasting-down time  No expensive no-load times occur (approx. 25% of full output)  No switching cycles occur, i.e. less mechanical strain on the components

Key data:  Compressor drive output: 60 kW  Capacity utilisation 70 full output share  30% no-load time at approx % full load consumption  Operating hours p.a. 4,000  Required operating pressure: 10 bars  Energy costs: 6 cents /kWh Example calculation of the potential energy savings from using an VARIABLE

Example: Average capacity utilisation (70%) of all compressors If a conventional compressor is operated at 70% of its maximum capacity, it means that the compressor operates with no load 30% of the time, during which it consumes roughly a quarter of the energy required for full load operation. This is an unnecessary waste of energy SCD - technology Conventional load / no-load regulation Consumption of the drive motor (%) LOADNO-LOADLOADNO-LOAD Example: 70% capacity utilisation Energy loss Energy loss Avoidance of no-load times The VARIABLE compressors can deal with this situation by setting the speed of the compression element to exactly the speed at which the required volumetric flow rate is generated. At the same time, the SCD technology of the drive system ensures that consumption matches the speed at all times. This enables VARIABLE compressors to significantly reduce energy costs when operating at 70% capacity.

Example calculation: Average capacity utilisation (70%) 60 kW compressor  70% full load  30% no-load time at approx % full load consumption 4,000 operating hours p.a. 4,000 operating hours p.a. x 30% no-load share x 25% of 60 kW x power costs (€/kWh) 1,200 operating hours x 15 kW x 6 (cents/kWh) 1,080 € saving p.a. 1. Avoidance of no-load times

Uneven networks result in frequent load / no-load changeovers: The compressor is relieved at each load / no-load changeover. The average relieve time is approx. 1 minute 45 kW 15 kW 100 % (60 kW) 25 % (15 kW) Drive output [kW] Time [min] approx. 1 min per pressure balance process No-load consumption after pressure balance process No-load consumption during pressure balance process 2. Reduced unloading frequency

Example calculation: Energy loss due to pressure balance times 60 kW compressor / pressure balance time approx. 1 min Receiver volume plant 80 L 15 load / no-load changeovers per hour operating hours p.a. Energy costs 0.06 € p. kWh 4000 operating hours p.a. x 15 load / no-load changeovers p.h. 60,000 load/no-load changeovers p.a. x 1 min 1,350 € saving p.a. Energy loss due to pressure balance times 60,000 min pressure balance time = 1,000 h pressure balance x 45 / 2 kW = 22,500 kWh x 6 cents 45 kW 15 kW 100 % (60 kW) 25 % (15 kW) Antriebsleistung [kW] Zeit [min] ca. 1 min pro Entlastung Leerlaufleistungsaufnahme nachEntlastung Leerlaufleistungsaufnahme bei Entlastung 45 kW 15 kW 100 % (60 kW) 25 % (15 kW) Drive ouput [kW] Time [min] approx 1 min pro pressure balance process No-load consumption after pressure balance process No-load consumption during pressure balance process 2. Reduced unloading frequency

Example calculation: Compressed air loss caused by unloading processes: 60 kW compressor Receiver volume plant 80 L 15 load – no-load changeovers per hour 4,000 operating hours p.a. Pressure balance from 10 bars (OVP) to 1 bar (OVP) 4,000 operating hours p.a. x 15 load / no-load changeovers per hour 60,000 changes p.a. x 440 L compressed air loss 26,400 m³ compressed air loss p.a. P1 x V1 = p2 x V2 p1 x V1 V2 = p2 11 bars (abs) x 80 L V2 = 2 bars (abs) V2 = 440 L (loss of compressed air per pressure balance process) Comment: It costs an average of 2 cents to produce 1 m³ compressed air 528 € saving p.a.  26,400 m³ x 2 cents = 528 € saving p.a. 3. Compressed air losses caused by unloading processes

The VARIABLE compressors run at a constant operating pressure (  p  0.1 bars), Since high pressure = high energy enormous amounts of energy can be saved here. 1 bar higher pressure ( 6 – 8 % higher energy consumption) Upper switching point Lower switching point Conventional load / no-load regulation Pressure bandwidth (bars): Example: Necessary operating pressure 10.0 bars VARIABLE Potential saving Constant network pressure

Example calculation: Required operating pressure: 10 bars Switch-on pressure for standard compressor: 10 bars Switch-off pressure for standard compressor: 11 bars  Pressure band = 1 bar Operating hours p.a.: 4,000 Compressor consumption 60 kW Power costs: 0.06 €/kWh 0.1 bar Pressure band optimisation: generated operating pressure: 10.1 bars  pressure band = 0.1 bar 1 bar higher pressure  6 – 8 % higher energy consumption  0.9 bars pressure band reduction  0.9 x 7% of 60 kW x 4,000 h x 6 cent/kWh 907 € saving p.a. 4. Constant network pressure oberer Schaltpunkt unterer Schaltpunkt Herkömmliche Last - - Leerlaufregelung Druckband (bar) Beispiel: erforderlicher Betriebsdruck 10.0 bar VARIABLE Einsparpotential 10,6 10,8 10,4 10,2 10,0 9,8 11,2 11,0 Upper switching point Lower switching point Herkömmliche Last Conventional load / no-load regulation - - Pressure bandwidth (bar) Example: Necessary operating pressure 10.0 – bars VARIABLE Potential saving 10,6 10,8 10,4 10,2 10,0 9,8 11,2 11,0 10,6 10,8 10,4 10,2 10,0 9,8 11,2 11,0

The compressor block drive is effected directly by the drive motor via a maintenance-free coupling without any transmission loss  Optimal power transmission and constant efficiency throughout the entire service life  Up to 99.9% efficiency  Less noise emission than with V-belt or gear machines  Great operational reliability  Very easy to maintain and service  Compared to V-belt drives there is no additional maintenance Savings: direct drive over V-belt drive:  V-belt drive (   96 – 97 %)  Direct drive(   99.9 %) 4,000 operating hours p.a., 60 kW motor  2.4 kW saving x 4,000 operating hours  kWh x 6 cents / kWh 576 € / saving p.a. 5. Direct drive

Compressed air lines always have leaks The amount of leakage depends, among other things, on the pressure in the pipelines. 10%! If pressure is reduced by 1 bar for example by means of speed control, these leaks are reduced by approx. 10%! % Studies have shown that the average leakage rate of a compressed air station is approx %. 6. Leak reduction

Example calculation: Basis: Required operating pressure: 10 bars Switch on pressure for standard compressor: 10 bars Switch-off pressure for standard compressor: 11 bars Operating hours p.a.: 4000 Compressor consumption 60 kW Volumetric flow rate approx. 8.5 m³/min Leak rate approx. 25% Power costs: 0.06 €/kWh Pressure band optimisation: generated operating pressure: 10.1 bars  0.9 bar pressure band reduction 1 bar pressure reduction = 10% leakage reduction  25% leakage of 8.5 m³/min  2,125 m³/min  m³/min leakage x 9% 0.19 m³/min leak reduction  0.19 m³/min leak reduction 0.19 m³/min x 4,000 h 45,600 m³ / year x 2 cents/m³ 912 € / saving p.a. 6. Leak reduction

Avoidance / reduction of: 1.No-load times:1,080 € 2.Pressure balance times:1,350 € 3.Pressure loss during pressure balance: 528 € 4.Pressure optimisation: 907 € 5.Direct drive: 576 € 6.Leak reduction 912 € Total saving p.a. approx.: 5,353 € by using a speed-controlled plant / VARIABLE! (Compared to: Standards at 70% capacity utilisation, 4,000 operating hours ) Total saving: an overview

Advantage of VARIABLE:  Many customers pay according to current peak values  enormous saving of power costs  Relief for “weak” networks  Enormous relief for the mech. components (“changeover shocks” do not occur)  Start-up at 110% rated torque load GENTLE STARTING STAR - DELTA DIRECT STARTING VARIABLE START-UP TIME [s] FULL-LOAD POWER CONSUMPTION BY MOTOR Full-load rated current Very energy-conserving start-up behaviour Other advantages

Companies with medium voltage transformer station: transformer station must be designed for the high peak currents By comparison Start-up current for of a 60 kW IEC motor > 380 A 95 A x 2.7  ( 257 A + changeover peaks (approx. 4-fold)  > 380 A Time [s] Power [A] Pulse-type starting: 60 kW plant with star-delta starting Continuous starting: VARIABLE 60 Inrush load = 2.7-fold rated current U Changeover peak, star to delta = 4-fold rated current Rated current 95 A, standard motor 60 kW 400 Other advantages - Very energy-conserving start-up behaviour

Owing to the special type of winding and the top grade sheet packets (high quality dynamo sheet), compared to IEC standard motors the ALUP SCD motor (motor protection class IP 55) is far more efficient over the entire load range Advantage of VARIABLE:  Power cost saving owing to less power loss  Less self-heating of the motor or smaller size  Flat curve at a high level, especially compared to a < 100 % capacity utilisation - Efficiency characteristics Efficiency characteristics VARIABLE Motor Efficiency characteristics of a standard asynchronous motor SCD drive motor 0,9 0,93 0,945 0,95 0,935 0,93 0,92 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0, Wirkungsgrad  Drehzahl 1/min Drehzahlbereich VARIABLE 100 5–13 bar 0,9 0,93 0,945 0,95 0,935 0,93 0,92 0 0,1 0,2 0,3 0,4 0,5 0,6 0,7 0,8 0, Efficiency  rpm 1/min Speed range VARIABLE 90 5–13 bar Typical efficiency characteristics of an asynchronous motor 0 0,2 0,4 0,6 0, Capacity utilisation [%] Efficiency

SCD frequency converter Advantage of SCD technology  Power cost saving  Relief to network  Minor power factor correction cos phi = constant cos phi = 0.9 (load) 0.5 (no-load) Idle current: Idle current (smaller than cos phi) must either  be paid for or  compensated. No-load cos  asynchronous operation cos phi  conventional technology asynchronous operation 0,0 0,2 0,4 0,6 0,8 1, Capacity utilisation [%] cos phi VARIABLE

Using the „energy savering duo“ VARIABLE + DIRECT Hours per week Volumetric flow (m³/min) VARIABLE DIRECTVARIABLE Interaction of several compressors

AIR CONTROL 3 Base load control Master Slave Slaves

Connection – networking BLCO (up to 9 compressors) RS 485 bus system all compressors are managed via a RS 485 bus system Data cable 3-wire, 0.5 mm², shielded Required signals: 1. Motor On / Off 2. Load operation / Idling 3. Fault message Module DE 200 F Module DE 200 F Module DE 200 F RS 485 interface Air Control 3 MASTER 3. RS 485 interface RS 485 interface Air Control 3 / BLCO

The advantages of speed control 1.constant pressure 2.exact output adjustment 3.avoidance of idling times 4.reduced unloading frequency 5.extremely energy-saving drive behavior 6.no peak loads 7.very good (high) motor efficiency 8.constant cos  9.direct drive 10.excellent p spezific 11.Air Control 3 12.flexible operating pressure 5 – 13 bar 13.reduction in leakage