The textile spinning mill is a continuously running unit that consumes a lot of electricity says Ashok Senthuraman and K Ramesh Babu

Introduction

The textile spinning mill is a continuously running unit that consumes a lot of electricity. Any small or big step to conserve electricity is always welcomed by mills. Every unit of electricity used in the industry is monitored.

The Bureau of Energy Efficiency's (BEE) aim is to monitor energy consumption and suggest efforts to reduce it. A kilowatt (kW) saved every hour equals saving Rs 50,000 annually.

This paper suggests that retrofit to carding cylinder under-loaded motor saves around 15 units per day, and Rs 30,000 is saved in a year for Rs 10,000 invested now. This is the first year return of energy conservation measure in this motor and it goes on. Whatever we implement to reduce energy loss in motors, it amounts to a decrease in the units per kg of yarn. First, we have to conduct an initial motor loading survey to assess the loading of motors - whether these are over-sized, rightly-sized or under-sized - to confirm the motor is rightly loaded.

Existing energy losses in carding cylinder motors

Mills have several carding machines of different brands and machines are getting advanced nowadays for higher productivity and lower power consumption. 'Well carded is half spun' is the mantra followed now by many mills in their spin plan. They allot in the spin plan to match each card to each ring frame production. Mills understand now that the carding machine has to be run at a slower cylinder speed to improve the overall carding and spinning quality of yarn.

A typical case study of carding cylinder motor in any textile mill is that the cylinder is a heavy rotating mass run by its motor. Hence all original equipment manufacturers (OEMs) of carding machines oversized their motor to say 5.5 / 7.5 / 9.3 kW rating to give a robust starting torque to the motor to rotate the cylinder.

All old carding cylinder motors are conventional ones having standard efficiency norms, peak efficiently at around 75 per cent band and are IE 1 versions as per latest international efficiency (IE) norms.

Standard motor has an efficiency droop, below its 50 per cent loading when run on delta mode. Therefore, the carding motor running at around 40 per cent loading now faces droop efficiency loss when running at 2.5 to 3 kW, i.e., at around 40 per cent loading of motor shaft rated 5.5 kW at the standard motor full rated efficiency of 85 per cent.

Earlier, mills wrongly applied the idea of star loading the motor, manually changing the motor terminals to star connection, and permanently running the motor always in start mode. This short-cut exercise made the motor hotter initially and within a few days, it got overloaded and burnt. The reason is the cylinder sides are choked with fluff. So instead of running in delta, since the motor was already in star connection, it failed due to wrong running in star when load is above 50 per cent. This means manually putting the motor in star mode is not the right solution. Automatic delta to star (Δ to Υ) is the cost-effective solution.