If you look back, you will see how much has changed for few hundred years. Now it’s hard to realize, how people lived without present-day blessings of civilization. It’s not just about comforts of home, but also about modern vehicles. Imagine that in 1980-s nowadays vehicles were just cinematic fiction. But now we know that some of those vehicles feed on electricity (electromobiles) and some even fly (aeromobile).
1. History of use of electromotors for cars
2. Types of electromotors
3. Pros and cons of electromotors
4. Failure inspection and repair
Well, aeromobiles might not be seen in wide use. But electromobiles are widely used today (f. e. Toyota Prius). So, why is electromotor so remarkable and how it won general recognition? To find answers to these questions, we’ll analyze its historical path, observe its types, pay attention to its pros and cons, various failures and what caused them.
1. History of use of electromotors for cars
Electromotor is an electric transducer, which is capable to transform electrical energy in mechanical. Its side effect is liberation of certain quantity of heat.
Such device is used as power pack of environmentally-friendly cars: electromobiles, hybrids. But, if we don’t take into account the “heart” of vehicles, then low-powered electromotors are present in simple petrol sedans (f. e. door actuators equipped with electromotors).
The idea of electric vehicle appeared in 1831, right after Michael Faraday discovered law of electromagnetic induction. The first engine based on this discovery was constructed by Russian physicist-inventor Moritz von Jacobi in 1834.
First vehicles equipped with electromotor, used as power pack, appeared in 1880-s and acquired overall popularity. It is easy to explain: at the turn of 19-20-th centuries, combustion engines had many disadvantages, which made the novelty look good, because its characteristics greatly exceeded the ones of combustion engine. Though, it wasn’t long until electromotors were forgotten for decades, due to petrol and diesel engine power increased. Another wave of interest to electromotors returned in 1970-s, in time of Great oil crisis. But it didn’t come to their mass production.
The real “Renaissance” of electromotors for hybrid vehicles and electromobiles was in first decade of 21-st century. Many factors were contribution to this: on one hand, onrush of computer technology and electronics allowed control and save battery charge, gradual oil fuel price increase on another hand, have made consumers to look for alternate sources of energy.
Generally, the whole history of electromotor can be divided into three periods:
First period covers 1821-1834 years. In this period of time first physical instruments appeared. The research of M. Faraday in 1821, which was done for studying of conduit interaction with current and magnet, showed that electric current causes the conduit rotation around magnet or vice versa – of magnet around conduit. The results of Faradays research confirmed possibility of electromotor construction. And many researchers suggested many options of its construction back then.
Second period of electromotors development began in 1834 and ended in 1860. It was characterized by invention of constructions with rotating motion of salient-pole armature. But shaft drive torque of such engines pulsed sharply. In 1834 first DC motor was invented by M.H. Jacobi. He implemented in it the principle of direct rotation of power pack moving element. In 1838 this engine was tested: it was installed on boat, which was let float freely down the river of Neva. This was the first time of practical use of Jacobi’s invention.
Third period of electromotors development is considered a time length from 1860 to 1887, which is connected to development of construction with circular non-salient-pole armature and sensibly constant driving torque. The invention of this period of time, made by Italian scientist Antonio Pacinotti is also worth mentioning. The Italian scientist developed construction of electromotor consisting of annular armature rotating in electromagnets geomagnetic field. The current supply was provided by rollers, electromagnetical winding plugged after armature winding. In other words: drives of electric machine were sequential. The differential peculiarity of Pacinotti’s electromotor was replacement of salient-pole armature with non-salient-pole.
2. Types of electromotors
There are many types of present-day electromotors. To the most renown refer:
- alternating and direct current motors;
- single-phase and polyphase motor;
- stepper motor;
- ac electronic motor and universal commutator motor.
Alternating and direct current motors, also universal commutator motors form a part of widely known magnetoelectric power packs. Let’s observe each type.
Direct current motors are electric and require direct-current power supply. In their turn, due to commutator availability, this type of electromotors is divided into commutator and brushless motors. Also, due to commutator, electric connection of chains of power pack fixed and moving part, which makes this element most vulnerable and complicated in maintenance.
According to wounding type, all commutator motor types divide in subtypes:
- independently wound power packs (from constant magnets and electromagnets);
- self-wound motors (shunt-wound, series-wound and dual-field motors).
Brushless motors (they are also called ac electronic motors) – these are devices submit in a form of sealed system, in which are used: rotor position sensor, control system, inverter (power semiconductor converter). The operational principle of mentioned motors is the same as of representatives of synchronous motor group.
Alternating current motors, according to its name, requires AC power. Synchronous motors have rotor rotating simultaneously with incoming power geomagnetic field, which allows using these motors under high power. There are 2 types of synchronous motors: stepper and ac reluctance motor.
Asynchronous motors, as previous ones, are type of alternating current motors, in which rotor speed is a bit more different from equivalent speed of rotary geomagnetic field. This type of electric motors is most used nowadays. Also all alternating current motors are divided into subtypes, depending on phase quantity:
- single-phase motors (they are started manually or equipped with accelerating coil, or they have phase-shift circuit);
- two-phase motors (incl. condenser motors);
- three-phase motors;
- polyphase motors.
Universal commutator motor is a device capable to feed on direct and alternating current. Such motors equipped only with series field winding powered up to 200W. Stator has laminated frame and is made of electrotechnical steel. The field winding has two operating modes: under alternating current it operates partially, under direct – in full capacity. Usually these devices are used for electric tools or other household devices.
The electronic prototype of direct current commutator motor is synchronous motor with rotor sensor and inverter. In other words, universal commutator motor is direct current motor, the field windings of which are connected in series and perfectly optimized for alternating current. Regardless polarity of incoming voltage, this type of power pack rotates one way, because due to rotor and stator windings connection in series, the poles of their geomagnetic fields shift simultaneously. This means that resultant moment is still directed one way.
Stator, which is made of low-coercitivity material, is used to provide working capacity under alternating current. To reduce vortex flow loss, stator construction is made of isolated plates. The advantage of alternating current capacity is: at low idle (start, reset) the input current and motor maximum torque is limited to stator winding inductive reactance.
For binding of general purpose motor mechanical characteristics usually used stator winding sectioning. In other words, for alternating current connection separate outputs are created and number of winding loops reduced.
Synchronous motor of crank motion operational principle is based on motor moving part fixed on stock. Alternating current goes through fixed windings and constant magnets that fall under geomagnetic field influence and move the stock back and forth.
One more classification that allows separate next types of electromotors is based on environmental protection. Due to this parameter, electric power packs can be armoured, enclosed and flameproof.
Armoured types are shielded with special plates, which protect the mechanism from various foreign objects. They are used for places without high humidity and special air composition (without dust, fog, gas or chemical compounds admixture). Enclosed types are placed in special case that protects from gases, dust, moisture and other elements that could harm the motor. These devices can be hermetic and non-hermetic.
Flameproof mechanisms are installed in body frame, which protects other components and prevents fire in case of motor explosion.
Selecting electromotor, pay attention to operation environment of the mechanism. If there are no foreign admixtures in the air, which can harm the motor, then it is better to purchase armoured motor instead of heavy and expensive enclosed one.
Integrated motor also should be mentioned as separate unit. Thos device doesn’t have its own body frame and only part of mechanism construction.
3. Pros and cons of electromotors
As any other device, electromotor has its flaws. And this means that except undeniable advantages there are specific disadvantages. Let’s start with pros, to which refer:
1. No transmission friction loss;
2. The effectiveness of driving motor reaches 90-95%, while this figure of combustion engine reaches only 22-60%;
3. Driving elecromotor torque peak is reached from the beginning of motion in the moment of motor start. That’s why there is no need in gearbox;
4. The cost of exploitation and maintenance of electromotors is lower, than of combustion engines;
5. No noxious exhaust gas;
6. High ecological level (no oil fuel, antifreeze substances or engine oil are used);
7. Minimal possibility of explosion in case of crash;
8. Simple construction and driving, outstanding reliability and undercarriage durability;
9. Possibility to charge from ordinary domestic socket;
10. Reduce of noise due to less number of moving parts and mechanical transmissions;
11. Increase of ride comfort with frequency interval of motor shaft rotation;
12. Possibility to recharge during the process of regenerative braking;
13. Possibility to use electromotor as brake (electro-magnetic brake function).
Considering everything mentioned above, we can make a conclusion that cars equipped with electromotor are 3-4 times more effective than cars with petrol engine. Though, as was already mentioned, there are some disadvantages:
- motor time per load is limited by battery maximum capacity. This means that in comparison to combustion engines electromotors have less mileage per one charge;
- electromotors are more expensive. But there is hope that with mass producing their cost will reduce;
- necessity to use additional accessories (f. e. quite heavy batteries (15-30kg in weight) and special rechargers meant for deep discharge).
As you can see, there are not many cons and in time their number will significantly reduce, because automotive engineers and designers will make improvements.
4. Failure inspection and repair
Unfortunately, even with all its advantages electromotor can breakdown, like any other device. The most widespread failures are:
Hum during start. The cause of this failure might be reduce or complete absence of electric potential in supply main; incorrect position of stator winding phase; motor lugging or driving gear failure. Of course, for dealing with this problem it is necessary to find and repair the breakdown or to make a re-connection, but according to correct scheme. Another way is to reduce the lug and repair the failure in driving gear.
Working motor stops abruptly. Possible reasons: voltage supply stopped; malfunctions of switchyard hardware or power system; jam of motor or driving gear; do stator diagnosis and repairmen, if necessary.
The shaft rotates, but it can’t reach normal rotational rate. Possible causes: one phase shut off during acceleration process; supply pressure reduced, motor suffers lugging. Power increasing will help to repair this type of failure; connecting of unlinked phase and remove motor overload.
Electromotor heats too much. This might be current overload; supply pressure increase or decrease; raise of environmental temperature; ventilation malfunction (obstruction of air channel); drive mechanism malfunction. Solutions: provide normal level of load; establish optimized temperature; clear air channels; repair driving mechanism.
Electromotor hums too much and doesn’t reach necessary rotational rate. Perhaps, it is turn-to-turn fault in stator winding; grounding of one phase winding; occurrence of short failure between two phases; phase abruption. There is only one way in this case – stator replacement.
Increased vibration of working motor. This might be: driving gear shaft with motor shaft compatibility defect; poor balancing of joint end or drive gear. To repair these failures you must improve compatibility, balance joint end and drive gear.
Bearing overheat. This might have been caused by: bearing damage; incorrect motor alignment with drive gear. Correct motor installation and bearing replacement will help to solve these problems.
Reduction of winding insulations resistance. This might be caused by winding maculation or dampen. Drying of components will solve this problem.