Compare the application of a DC and AC motor for two contrasting modern electrical installations.

An electric motor is an electrical machine that converts electrical energy into mechanical energy. The reverse of this would be the conversion of mechanical energy into electrical energy and is done by an electric generator.

In normal motoring mode, most electric motors operate through the interaction between an electric motor's magnetic field and winding currents to generate force within the motor. In certain APPLICATIONS, such as in the transportation industry with traction motors, electric motors can operate in both motoring and generating or braking modes to also produce electrical energy from mechanical energy.

AC Motors are commonly run by an AC variable frequency drive, an AC electric motor operates by applying alternating current (AC) power to the electric motor. An AC electric motor consists of several parts but the main parts are the stator and rotor. In the other hand, DC Motors DC electric motors are powered from direct current (DC) power and are mechanically commutated machines. DC electric motors have a voltage induced rotating armature winding, and a non-rotating armature field frame winding that is a static field, or permanent magnet.

The AC electric motor’s stator has coils that are supplied with the alternating current and produces a rotating magnetic field. The AC electric motor’s rotor rotates inside the electric motor’s coils and is attached to an output shaft that produces torque by the rotating magnetic field. There are two different types of AC electric motors and each of them uses a different type of rotor. The first type of AC motor is called an induction motor (also known as an asynchronous motor).

DC electric motors use different motor connections of the field and armature winding to produce different speed and torque regulation. Unlike AC electric motors, DC electric motor speed can be controlled within the winding by changing the voltage applied to the DC motor armature, or by adjusting the field frame current.

An induction motor uses a magnetic field on the rotor of an induction motor that’s created by an induced current. The other type of AC motor is called a synchronous motor and rotates precisely at the supply frequency or on a sub-multiple of the supply frequency.

Most DC electric motors today are manufactured to be controlled with industrial electronic DC drives. DC electric motors are still used in many APPLICATIONS across the globe such as paper producing machines, and steel mill rolling machines.

AC and DC Motors DC motors are usually seen in applications where the motor speed needs to be externally controlled. AC motors work best in applications where power performance is sought for extended periods of time. All DC motors are single phase, but AC motors can be single phase or three phase.

AC and DC motors use the same principle of using an armature winding and magnetic field except with DC motors, the armature rotates while the magnetic field doesn’t rotate. In AC motors the armature does not rotate and the magnetic field CONTINUOUSLY rotates.

In some applications today, DC electric motors are replaced by combining an AC electric motor with an electronic SPEED CONTROLLER, known as variable frequency drives. DC electric motors are replaced with an AC electric motor and an electronic speed controller because it is a more economical and less expensive solution.

Found in applications as diverse as industrial fans, blowers and pumps, machine tools, household appliances, power tools, and disk drives, electric motors can be powered by direct current (DC) sources, such as from batteries, motor vehicles or rectifiers, or by alternating current (AC) sources, such as from the power grid, inverters or generators. Small motors may be found in electric watches. General-purpose motors with highly standardized dimensions and characteristics provide convenient mechanical power for industrial use. The largest of electric motors are used for ship propulsion, pipeline compression and pumped-storage applications with ratings reaching 100 megawatts. Electric motors may be classified by electric power source type, internal construction, application, type of motion output, and so on.

The difference between AC and DC electric car motors, and which one will work best:

Direct current (DC) motors are the most popular choice for EV conversions, for a few good reasons. First, they are the least expensive and most readily available, and has enough power for a small or medium-sized car.

The DC Series electric motors are known for their high torque capacity from standstill. While combustion-style engines lack power when getting started, Applications such as diesel locomotive traction motors and drill motors (both of which are usually DC electric) help illustrate this feature. While torque is considered a benefit, though, continuous hill-climbing high-load driving with a DC motor is not ideal; AC motors do this much better. This is because DC motors have permanent magnets mounted on the inner surface of the motor housing. These magnets are able to provide high torque, but they don’t transmit heat well, leading to heat buildup in the windings.  DC continuous operating horse power is substantially less than peak horse power (HP).

Alternating current (AC) motors aren't used in DIY electric cars nearly as often as DC motors; it isn't because they don’t perform well. On the contrary, AC motors is better in many ways — including continuous power for hill climbing, regenerative braking, wide range, light weight and overall power. AC motors just tend to be a lot more expensive than DC. Why it’s so expensive? A few reasons why it’s expensive are: one of which is the fancy converter system that changes the direct current coming out of EV batteries into an alternating current. Another is the sophisticated exchange system that allows for regenerative braking. As mentioned previously, AC motors are more efficient, and when combined with regenerative braking they are a clear winner for distance applications.

The speed of DC motors is controlled using pulse width modulation (PWM), a technique of rapidly pulsing the power on and off. The percentage of time spent cycling the on/off ratio determines the speed of the motor, e.g. if the power is cycled at 50% (half on, half off), then the motor will spin at half the speed of 100% (fully on). Each pulse is so rapid that the motor appears to be continuously spinning with no stuttering.

Risk Assessment and Controlling Hazards

Justify the methods used in industry to deal with hazards, with regards to legal requirements.

Hazards exist in every workplace, but how do you know which ones have the most potential to harm workers?

The hierarchy of risk control is a system of control measures used to eliminate or reduce exposure to hazards, which has five levels of control measures. It is used when undertaking a risk assessment, to decide on which precautions are needed to control the risks posed by the hazards.

The most effective measure is at the top of the hierarchy and the least effective is at the bottom. So the idea is that you start from the top of the hierarchy in choosing your control measures, and work your way down. In most cases a combination of control measures from the hierarchy are chosen to effectively reduce the risk posed by a hazard. The hierarchy of risk control is useful in determining which control measures are appropriate. The most effective control to deal with a hazard is to eliminate it, but that is not always possible. Some hazards cannot be eliminated. So, the aim of implementing the hierarchy of risk control is to get as many control measures in place so that the risk from a hazard is reduced "as low as reasonably practicable".

1.Eliminate the Hazard The best way to control a hazard is to eliminate it. This can be achieved by making changes to the work process so that the task is no longer carried out, or by physically removing the hazard altogether. Elimination is the most effective way to control hazards and should be used whenever possible. However, it can also be the most difficult to implement, especially if the process is still at the design or development stage. For example, dangerous machinery is often required, and while it can be made safer, it can't be eliminated.

2. Substitute One Risk for a Lesser One Substitution is the second most effective method for controlling hazards. It is similar to elimination but involves the substitution of one risk for another. For example, one hazardous chemical could be swapped for one with less risk. However, for substitution to be effective, the new replacement must not produce greater hazard. Another type of substitution involves using the same chemical, but in a

different form; for example, a chemical in its powder form can be more hazardous (inhalation hazard) than in its pellet form.

3. Isolate the Hazard From the Person at Risk Isolation involves separating the hazard in time or space from the person or persons at risk. This can be achieved by isolating the hazard through containment or enclosure. These methods aim to keep the hazard in and the worker out.

4. Use Engineering Controls If a hazard cannot be eliminated nor isolated and a safer substitute cannot be found, the next best approach is the use of engineering controls. Engineering controls are implemented by making changes to the design of an equipment or process to minimize its hazard. Although engineering controls are the most expensive solution, they provide the advantage of reducing future cost. The two basic types of engineering controls are process control and ventilation. Process control involves changing the way a job activity or process is performed to reduce hazards. Ventilation is a method of control that adds and removes air in the work environment.

5. Use Administrative Controls If engineering controls cannot be implemented, administrative controls should be considered. However, because they do not actually remove or reduce the hazards, they are less effective in comparison to other control measures in the hierarchy. There are usually also many difficulties associated with the implementation and maintenance of control measures. Administrative controls involve making changes to the way in which people work and promoting safe work practices via education and training. Administrative controls may involve training employees in operating procedures, good housekeeping practices, emergency response in the event of incidents such as fire or employee injury, and personal hygiene practices such as the washing of hands after contact with hazardous materials.

6. Use Personal Protection This is the least effective method of controlling hazards because of the high potential that personal protective equipment (PPE) will become damaged. If PPE is inadequate or fails, the worker is not protected. PPE can also often be uncomfortable, which can place an additional physical burden on the worker. Therefore, PPE should only be used in combination with other control measures from the hierarchy or if there are no other more effective ways to control the hazard. Examples of personal protective equipment include respirators, gloves, protective clothing, hard hats, goggles and ear plugs. By identifying hazards at your workplace, you will be better prepared to control or eliminate them and prevent accidents, injuries, property damage and downtime.

Accurately identifying, assessing, and controlling hazards is an essential part of a properly functioning occupational health and safety program. The health and safety regulation act 1974 will help employers and managers to improve their health and safety performance. They will learn effective and proven methods of hazard identification, assessment, and control.

A very common method used to deal with hazards is risk assessment. A risk assessment is a systematic process of looking at work activities, considering all the hazards possible and deciding on suitable control measures to prevent loss, damage or injuries in the workshop. It shows whether you have taken enough precautions and shows you what more needs to be done to ensure that the workplace has safe environment.

The risk assessment is required by law as it lies under the health and safety at work regulations 1999, which lies under the legislation health and safety at work etc. 1974. A risk assessment is performed by a governing body which comes to the workplace, known as the health and safety executive {HSE}.

Due to the existence of electricity inside the engineering workshop, it will be necessary to protect the worker and he visitors from the hazards caused by electricity. Electricity is a major hazard - not only can it kill directly, through shocks, it can also cause fires and explosions. So these regulations aim to impose duties to limit the risks involved in using electricity at work.

The manager or employer should Carries on the responsibility of protecting the staff and visitors inside his workshop from the hazards and that is applied under Electricity at work regulations 1989, therefore the employer should provide the suitable equipment for his employee and visitors to reduce the electrical hazards.

During the work some accident could be happen so the employer and the employee should be ready to carry on that accident and disposition as fast as possible to reduce the hazard which hit someone inside the workplace. That is apply to Health and Safety (First Aid) Regulations 1981 the manager should provide the specific lessons to his employee to let them know what should they do if any accident happen inside the workshop.

Give training to the staff would reduce the hazard dramatically and that give guarantee to the manager that he have employees subliminal for what they have to do to eliminate the hazard as much as possible between the comings of responsible authorities.

the employer or manager should know what kind substances he have inside his workshop and if its might cause harm for the visitors or workers that is apply for Control of Substances Hazardous to Health Regulations 2002 (COSHH), the workshop is a place contains too many different kinds of substances and there is some substances could causes hazards and the manager should take that as a serious issue because this substances might cause death when exposure to these substances. The COSHH is include the substances such as chemicals products containing, chemicals, fumes, dusts, vapours, mists, nanotechnology, gases and asphyxiating gases and biological agents (germs).