Lenze SMD Frequency Inverters Unstick Glue Production

Lenze Americas 12th Dec 2022

Lenze SMD Frequency Inverters Unstick Glue Production

Costly downtime reduced on PVA emulsion pumps

Lenze's SMD inverters have solved a problem of costly downtime, as a result of motors burning out on PVA emulsion pumps at Grosvenor Chemicals, which manufactures a diverse range of chemicals and pharmaceutical intermediates at its UK plant.

The PVA emulsion pumps are used in the production of glue at Grosvenor's Huddersfield factory. Previously they were driven by fixed speed electric motors, which had problems resulting from the variation in PVA emulsion viscosity across different products. This was causing motor overloads, particularly on restarts, with the consequent problems of premature motor failures, and costly downtime.

The solution to this problem was Lenze VFD inverters. These were supplied in very compact panels – an arrangement possible due to the very small footprint of the smd series (only 114mm x 171mm for 5.5kW). The inverters are rated at 5.5kW and 7.5kW; and are equipped with a footprint filter to meet RFI class 'A' requirements. A separate keypad is door mounted to give the operators an easy way to change the pump speed.

The smd units provide a soft start facility for the pump motors, and can hold 150% rated torque for up to 60 seconds. They also provide further protection via their built-in thermal motor monitoring, which allows a shutdown with error message if the motor begins to overheat, without causing any motor change.

When smaller HP brake modules (0.33 - 10 HP) are applied, protection is provided by the thermistor and the software algorithm. In the larger HP brake modules (15 - 30 HP) protection is provided by the software algorithm only. For the SC series and SMV series NEMA1 drives, the DB circuit is completely external to the drive inside a separate module. The DB module is independent of the drive’s normal function and ratings. Current sharing or connecting the DC bus terminals between multiple drives is not allowed. Use larger DB kits or connect modules in parallel to keep the same drive size. Lenze-AC Tech offers modules based on HP and voltage rating. This means even a 15HP Dynamic Brake module could be used on a 5HP drive.

A very common question from customers is how to properly size dynamic braking for a large inertial load. In order to do this, gather all the (drive) system mechanical and electrical characteristics to properly calculate the DB value. Whether or not the DB resistor bank will meet these requirements can only be determined by analyzing the entire mechanical system of the driven equipment.

12th Dec 2022 Lenze Americas

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