Lenze frequency inverters adapted to niche markets

The importance of frequency inverters in the industrial machinery market is progressively increasing. Forces driving the market are the increase in automation and also the recognition of the role inverters can play in saving energy. Over the last five years inverter sales have outgrown the UK sales of machinery by about 15%. This wider use of frequency inverters is bringing them into smaller, niche markets and inverter design is adapting with user-friendly features that suit these markets. This is illustrated by the Lenze SMV inverters with a wide range of supply voltages and functions that were previously controlled by a supervisory PLC such as sequencing and pump rinse functions. The SMV range of frequency inverters is manufactured by Lenze in North America, using the AC Tech brand name on that continent. It is available in IP31 and IP65 variants that cover a power range of 0.25 to 37kW (a maximum of 22kW for the IP65 variant). These designs are established and the performance is proven with sensorless vector control, high dynamics and a 200% overload capacity. There are built-in features to save time and cost such as the pluggable memory chip that can download all the drive parameters in seconds. Now the functionality has been extended with new features that suit particular market areas. The SMV has a range of supply voltages that is particularly broad. Models for three phase supply are available for nominal supply voltages from 240 up to 600V, the top end suiting machines to be exported to territories with high supply ranges. Of course a 10% tolerance is available on top of these voltages. When it comes to single phase supplies, standard models suit 220-240V as is commonplace in Europe. However an additional model includes a 'voltage doubler' that accepts 120V single phase input and outputs 3phase at 240V. Again this suits exports of machinery to territories with more unusual supplies and allows the machine manufacturer to make simple inverter changes rather than change the motor/geared motor. The SMV has even been proven in the Australian outback with a single wire 480V AC supply and an earth literally through the ground, that is the soil. Customers running repetitive cycles can make use of a new sequencer function that is standard in the SMV drives. Up to 16 individual profiles of ramp time, speed target and time at speed can be pre-programmed into sequence. Following a start signal the sequence runs either once or is repeated. Each of the 16 profiles is stepped through either automatically or manually following an external trigger signal. A stop signal interrupts the sequence at any point and a pause signal holds the sequence in the current active profile. The sequencer function can remove the need for an external controller in simple cyclic applications, ideally where the load is steady and there is no requirement to follow a precise path. Examples are industrial gates and doors where limit switches can detect the position for the end of the sequence, also cycling of washing and plating machinery. Another user-friendly feature available at no extra cost in the SMV inverters is motor flux braking. This suits infrequent stops as the motor is used as a heat sink. Effectively the inverter drives the motor to stop on a deceleration ramp whilst over-fluxing the motor. A high magnetisation current causes the braking energy to appear as heat in the motor. The advantage of motor flux braking is the simplicity and reduction in system costs; no external chopper or braking resistors are required. Ideal applications are conveyors, saws and fans. The SMV now has an enhanced PID sleep mode function where the drive can enter the sleep mode triggered by a user specified feedback value. There is a choice for the motor to coast to stop, to ramp to stop or be braked. Recovery from the sleep mode is possible based solely on a feedback value set by the customer. Typical applications are fans in ventilation and HVAC systems, pumps, escalators and rotating doors. Pump and fan applications can also take advantage of a new 'pump rinse and purge' function. This prevents the build up of sludge on pump impellors which means reduced wear and higher efficiency. Customers can set a time delay for the rinse/purge to start after entering sleep mode. Then the motor follows a sequence of ramp to speed, hold, then ramp to stop. With ventilation systems this also avoids build up of dirt on fan blades, for example when systems are shut down at night. The rinse/purge function improves efficiency and is a particular requirement for smoke detection systems in high rise buildings. With a wide power range 0.25 to 37kW, wide range of supply voltages and two levels of protection, IP31 and IP65, the SMV inverters are particularly adaptable to most types of industrial machinery. Now new functions are built into the drives at no extra cost giving the ability to reduce external components and controls. This new functionality is particularly beneficial for pumps, fans and machines that run repetitive cycles. For more information, contact Geoff Spear at Lenze Ltd, Tel: 01234 321227 Fax: 01234 753220 Email: gspear@lenze.co.uk