Applications: Industry
Transducers are tucked away within the heart of power electronics industrial applications. Without being aware of it, people probably walk by and even use several LEM transducers each day. Transducers are present in elevators, forklifts, machines tools, printing machines and in all equipment using industrial drives on motors for efficient control and regulation.
The transducer is used to measure the constantly varying current in order to feedback for control purposes. This leads to an accurate and smooth adjustment of equipment operation. With a machine tool, the current flow increases abruptly when the tool starts working on the part to be machined. The better and faster the feedback signal, the smoother the control of equipment information. (See application note "Efficiently control your compact machines”.)
The following examples may serve as an illustration:
Elevators
Whether in low-rise buildings or soaring skyscrapers, elevators are everywhere. When entering an elevator, a dedicated motor opens and closes the door. To operate safely, the door must retract if a person or an object hinders closure. Obstacle detection is often performed by current transducers in the motor wires. Obstacles cause a higher torque and therefore a higher current in the motor; this extra current is detected and triggers the open-the-door signal. (See application note “Ensure the safety door openers with current measurement”.)
In elevators, the signals provided by transducers cause the motor to adjust its torque to the effective weight of the cabin for smooth acceleration and stopping. Signals are also used to lift the cabin exactly level to its destination. Intelligent power control is also a way of optimizing the use of electricity. Upgrading variable speed drives of electrical motors brings substantial energy savings.
Solar panels
In solar panels, the generated electricity can be used for autonomous installations, remote from the distribution grid, which charge a battery. This is commonly referred to as an ‘off-grid system’. In contrast, the grid-connected system feeds energy back into the grid.
In photovoltaic panels, transducers control the energy flow to the grid and are used for ensuring the safety of equipment and people. (See application note “Solar inverters”.)
Forklifts
Modern forklifts are battery driven and need to be fast, strong, precise and agile whilst moving. They are also often used outdoors, so they need to be robust and able to cope with varying weather conditions.
Electric motor drives control the various important functionalities of the forklift such as the speed of the vehicle as well as the ascending and descending of the fork. For safety and stability, it is vital that the fork will lift with the same precision and speed – no matter the weight it has to transport. By measuring the current demanded by the fork motor, LEM transducers control the speed and precision of the fork. Analyzing the amount of current necessary for the action, they adjust the amount of power needed to lift the fork. The result is a smooth and steady operation.
At the same time, the current transducers check the status of the battery charge. This allows an optimization of the batteries’ efficiency and load cycle, enabling the forklift to go further after charging and also effecting the most rapid recharging possible. Since the transducers measure the current without intrusion in the circuitry, they also have a positive impact on the total energy consumption of the forklift.
LEM’s open loop current transducers offer clear advantages to customers. They are very small and can be perfectly integrated into the on-board electronics. They shorten installation time significantly as they do not have to be built into the application.
Wind turbines
The blades of modern powerful on- and off-shore wind energy turbines drive a generator. This converts the mechanical energy from the turning blades into electricity. The electricity produced needs to be fed safely into the grid.
The grid needs to be supplied with continuous power at a controlled frequency and voltage. To do this it is essential to transform and to optimize the generation of electricity from the wind turbine. Current transducers are key components of every converter in wind energy turbines, as they enable optimal control and protection to feed the grid.
To ensure the generators can work in the most efficient way, electric motors actively turn the nacelle and the rotor into the wind. In addition, an active power control system adjusts the rotor blades within their longitudinal axis using low-power electrical drives for pitch settings. This is how the maximum wind power can be transformed into useful electricity.
Transducers in the power converters, provided by LEM, continuously measure the current in order to optimally position the turbine to the wind. Thanks to its in-depth knowledge, LEM offers a wide range of products, including different sizes and parameters, that are very well adapted to the specific needs and mechanical requirements of the application. (See application note “Generation yield improvement, control and protection in modern windmills”.)
Gas co-generators
The amount of energy consumed in the industrial, commercial and residential sectors continues to rise. Gas co-generators can contribute substantially to slowing down this trend.
A gas co-generator uses natural gas to generate electricity and hot water.
The process works by using natural gas to generate steam which is used to drive a turbine and so generate electricity. Any extra heat can be used for hot water or the heating system – just like a water boiler.
The steam produced by the gas water heater drives a turbine, which in turn generates electricity through an inverter. This inverter is connected directly to the electrical network of the household. Specific, high accuracy LEM transducers measure the output current of the inverter, and ensure that it is perfectly matched with the electrical network. In parallel, newly developed transducers using flux-gate technology, ensure that leakage current stays within safety limits.
LEM is the preferred supplier for this application due to their products’ high performance and reliability. For the first time, LEM’s non-intrusive technology allows the measurement of very small current flows with high accuracy at reasonable costs.
Applications made up of power electronics are following this need to control, regulate and protect at the best with the best components integration. This is also the case for the various power supplies (see application note "Quality improvement & time savings thanks to current measurement") such as:
- UPS (Uninterruptible Power Supply)
- SMPS (Switched Mode Power Supplies)
- Telecom power supplies (see application note “Control & modernize your existing systems”)
- Airports lighting power supply
- Lighting power controller