How Repair Old Electric Motor

Electric motor

Motor structure
Working principle
Motor classification
Types of electric motors
- Commutator motors
- Commutatorless motors
Special motors

The main parameters of the motor
- Motor torque
- Motor power
- Efficiency
- Rated speed
- Moment of inertia of the rotor
- Rated voltage
- Electrical time constant
- Torque-speed bend
Comparison of motors characteristics
Application fields
Manufacturers

An electric motor - is an

electrical machine by which electrical energy is converted into mechanical free energy, for driving various mechanisms. The electric motor is the primary chemical element of the

electric drive.

In some operating modes of the electric drive, the electric motor performs the reverse energy conversion, that is, it operates in the fashion of an electric generator.

By the type of created mechanical motility, electric motors are divided into rotating, linear, etc. Past an electric motor, a rotating motor is most often meant, since it has received the greatest use.

The field of science and technology studying electrical machines is electromechanics. It is considered that its history begins in 1821 when the first electric motor was created by 1000. Faraday.

Motor construction

The main components of a rotating electric motor are the stator and the rotor. The stator is the fixed part. The rotor is the rotating part.

Standard construction of the rotating motor

For most electric motors the rotor is located inside the stator. Electric motors in which the rotor is located exterior the stator are chosen inside out electric motors.

Working principle of the motor

1. According to

Ampere's law, a forcefulness F will deed on a usher with a electric current I in a magnetic field.

two. If a conductor with current I is bent into a frame and placed in a magnetic field, then the 2 sides of the frame, which are at right angles to the magnetic field, will feel oppositely directed forces F.

3. The forces acting on the frame, create a torque or moment of forcefulness, rotating it.

4. The armature of the produced electric motors has several turns to provide greater abiding torque.

v. The magnetic field can exist created both by magnets and electromagnets. An electromagnet is usually a wire wound on a core. Thus, co-ordinate to the

Faraday's law of induction, the electric current flowing into the frames will induce a electric current in the windings of an electromagnet, which in plough volition create a magnetic field.

Working principle of single-stage induction motor
Working principle of a three-stage induction motor
Working principle of a synchronous motor

Motor classification

Rotating electrical motor
Self-Commutated			Externally Commutated
Mechanical-Commutator Motors		Electronic-Commutator Motors¹	Induction motors	Synchronous motors
AC	DC	AC^two	Air-conditioning
Universal motor Repulsion motor	Electrically excited DC motor (wound stator) Winding connection Separately excited Serial Shunt Chemical compound PM DC motor	BLDC motor (Brushless motor + EPC \|+ RPS) SRM (Reluctance motor with salient pole rotor and with the concentrated stator winding + EPC \|+ RPS)	Three phase (polyphase) SCIM WRIM Two stage (condenser motor) Single phase with auxiliary winding with shaded-pole with asymmetrical stator	WRSM PMSM IPMSM SPMSM Hybrid SyRM Hysteresis Hybrid SyRM-PM Hysteresis-reluctance Stepper³
Unproblematic electronics	Rectifier, transistors	More elaborate electronics	Most elaborate electronics (VFD) when provided

Note:

This category does not stand for a dissever class of electrical motors, since the devices in the category under consideration (BLDC, SRM) are a combination of a brushless motor, an electrical converter (inverter) and, in some cases, a rotor position sensor (e.g. Hall sensors). In these devices, the electric converter, in view of its low complexity and minor dimensions, is commonly integrated into an electric motor.
The electric motors used in BLDC and SRM are AC motors. However, due to the presence of an electric converter in these devices, they are continued to the DC power filigree.
A stepper motor is non a dissever motor grade. Structurally, it is the PMSM, SyRM or the hybrid SyRM-PM.

Types of electric motors

Commutator motors

Сommutator machine is a rotating electric machine, which has at least one of the windings involved in the main process of energy conversion, is connected to a collector [one]. In a collector motor, the brush-collector associates performs the function of a rotor position sensor and a current switch in the windings.

Universal motor

Can piece of work on AC and DC power supply. It is widely used in hand-held power tools and in some household appliances (in vacuum cleaners, washing machines, etc.). In the Us and Europe, it was used equally a traction motor. Received a wide distribution due to its small size, relatively low price and unproblematic command.

Brushed DC electrical motor

An electric car that converts straight electric current electric energy into mechanical free energy. The advantages of the DC motor are high starting torque, speed, the power to smoothly control the rotational speed, the simplicity of the device and control. The disadvantage of the motor is the need for maintenance of collector-brush assembly and express lifetime due to wear of the collector.

With permanent magnet

With wound stator

Commutatorless motors

Commutatorless electric motors can have contact rings with brushes, so do not confuse commutatorless electrical motors and brushless electrical motors.

A brushless machine is a rotating electric motorcar in which all electrical connections of the windings involved in the basic process of energy conversion are carried out without sliding electric contacts [ane].

Induction motor

The most common electric motor in the industry. The advantages of the electrical motor are the simplicity of pattern, reliability, low cost, high service life, high starting torque, and overload capacity. The disadvantage of an induction motor is the complexity of the rotational speed control.

Single phase
Two phase

3 stage

Special electrical motors

Servomotor

Servo motors are non a dissever class of motors. As a servomotor can be used DC and AC electrical motors with a rotor position sensor. The servo motor is used in the servo-mechanism for precise command of the angular position, speed, and dispatch of the actuator. To operate, a servomotor requires a relatively complex control system, which is usually developed specifically for a servo bulldoze.

The principal parameters of the motor

Motor torque
Motor power
Coefficient of efficiency
Rated speed

Moment of inertia of the rotor
Rated voltage
Electric time constant
Torque-speed curve

Motor torque

Torque (synonyms: a moment of forcefulness) is a vector physical quantity equal to the production of the radius-vector, drawn from the centrality of rotation to the betoken of application of force, by the vector of this force.

where K – torque, Nm,
F – forcefulness, Due north,
r – radius-vector, k

Tip: Rated torque 1000_r, Nm, determined by the formula

where P_r – rated motor power, W,
northward_r - rated speed, min^-one [4]

The initial starting torque is the motor torque at kickoff-upward.

Tip: In the English system of measurement, force is measured in ounce-strength (oz, ozf) or pound-force (lb, lbf)

1 oz = 1/16 lb = 0,2780139 N
1 lb = 4,448222 N

torque is measured in ounce-force inch (oz∙in) or pound-force inch (lb∙in)

1 oz∙in = 0,007062 Nm
1 lb∙in = 0,112985 Nm

Motor ability

Motor power is the useful mechanical power at the motor shaft.

Mechanical power

Power is a physical quantity that shows what kind of piece of work the machinery performs per unit of time.

where P – power, West,
A – work, J,
t - time, south

Work is a scalar physical quantity equal to the production of the projection of the forcefulness on the direction F and the path due south traversed by the point of application of force [ii].

where s – displacement, m

For rotational motion

where – bending, rad,

where – angular velocity, rad/s,

Thus it is possible to calculate the value of mechanical power on the shaft of a rotating electric motor.

Tip: Rated value is the value of the electrical device parameter specified by the manufacturer, at which it should work, which is the source for counting deviations.

The energy conversion efficiency of the electric motor

Free energy conversion efficiency of the electric motor is a characteristic of the machine effectiveness in relation to the conversion of electrical free energy into mechanical energy.

where – efficiency of the electric motor,
P_one - input power (electrical), Вт,
P₂ - useful output power ( mechanical), W

losses in electric motors

electric losses - in the form of heat as a issue of heating of conductors with the current;
magnetic losses - core remagnetization losses: eddy electric current losses, hysteresis, and magnetic aftereffects;
mechanical losses - friction losses in bearings, on ventilation, on brushes (if any);
additional losses - losses acquired past college harmonics of magnetic fields arising due to the tooth structure of the stator, rotor and the presence of higher harmonics of the magnetomotive force of the windings.

The efficiency of the electrical motor can vary from x to 99% depending on the type and design.

The International Electrotechnical Commission determines the requirements for the efficiency of electrical motors. According to the standard IEC 60034-31: 2010, four efficiency classes are divers for synchronous and induction electric motors: IE1, IE2, IE3, and IE4.

Rated speed

where n - is the rotation speed (frequency) of the electric motor, rev/min

Moment of inertia of the rotor

The moment of inertia - a scalar concrete quantity, which is a measure out of the inertia of a body in a rotational move effectually an axis, is equal to the sum of the products of the masses of material points and the squares of their distances from the centrality.

where J – the moment of inertia, kg∙chiliadⁱⁱ,
m - mass, kg

Tip: In the English system of measures, the moment of inertia is measured in ounce-force-inch (oz∙in∙s²)

ane oz∙in∙s² = 0,007062 kg∙chiliad²

The moment of inertia is associated with the moment of force as follows

где – angular acceleration, s^-2 [two]

Rated voltage

Rated voltage - is the voltage to which the power grid or equipment is designed and to which their characteristics is referred [3].

Electrical time constant

The electrical time constant is the fourth dimension counted from the moment a DC voltage is practical to the electric motor, during which the electric current reaches a level of 63.21% (1-1/eastward) of its terminal value.

где – fourth dimension abiding, s

Torque-speed curve

The torque-speed bend (mechanical feature) of the motor is a graphically expressed dependence of the shaft speed from the electromagnetic torque at a DC supply voltage.

Comparing of characteristics of externally commutated motors

Below are the comparative characteristics of externally commutated electric motors, in terms of use as traction motors in vehicles.

Comparison of torque-speed curves of unlike types of electrical motors with a express stator current
The dependence of ability from the shaft rotation speed for motors of unlike types with a limited stator electric current

Parameter	SCIM	SPMSM	IPMSM	SyRM-PM	WRSM
Abiding power over speed range
Torque per stator current
Efficiency over consummate operating range
Weight

Annotation:

Orange color is depression index; yellow is medium; light yellow is high.

In accordance with the above indicators, a hybrid synchronous electric motor, namely a synchronous reluctance electric motor with incorporated permanent magnets, is most suitable for employ as a traction electric motor in the automotive manufacture (the choice was made for the BMW i3 & BMW i8 concept). The use of reactive torque provides loftier power in the upper speed range. Moreover, such a motor provides very high efficiency in a wide operating range [7].

Electrical motors applications

Electric motors are the largest consumers of electricity in the globe, they account for about 45% of the total electricity consumed [half dozen].

industry: pumps, fans, compressors, conveyors, driving strength for other machines, etc.
structure: pumps, fans, conveyors, elevators, heating, ventilation and air-conditioning systems, etc.
consumer devices: refrigerators, air conditioners, personal computers and laptops (hard drives, fans), vacuum cleaners, washing machines, mixers, etc.

Motor	Functions	Application
Rotating electric motors	Pumps	H2o supply and drainage systems
		Heating, cooling and chilling systems, HVACⁱ, irrigation systems
		Sewage system
		Oil pipeline
	Fans	Room air supply and frazzle, blowers, HVAC^one
	Compressors	Cooling machines for air-conditioning and commercial freezers, refrigerators and freezers, HVAC^ane
		Compressed-air storage and distribution system, pneumatic systems
		Liquification systems
	Rotating, mix, stir	Roller, rotors: metallic, rock, plastics processing
		Extruder: aluminium, plastics processing
		Textile handling: weaving, washing, drying
		Mixers, stirring: nutrient, colour, plastics
	Ship	Passenger elevator, escalator, conveyor
		Goods lift, cranes, hoists, conveyor
		Vehicles: train, tram, trolley, cars, buses, electrical cars, bikes and bicycles, cog bicycle train, cablevision motorcar, ropeway
	Angular position (stepper motors, servomotors)	Valve (open/close)
	Angular position (stepper motors, servomotors)	Servo (setting position)
Linear motors	Open/shut	Valve
	Sort	Production
	Grab and place	Robots

Note:

HVAC - Heating, Ventilation, & Air Workout

Electric motor manufacturers

A land	Manufacturer	Induction motor		Synchronous motor				Universal	Brushed DC motor
A land	Manufacturer	SCIM	WRIM	WRSM	PMSM, servo	SyRM, Hysteresis	Stepper	Universal	Wound field DC motor (wound stator)	PMDC motor (permanent magnet stator)
Switzerland	ABB Limited
United states	Allied Motility Technologies Inc.
U.s.a.	Ametek Inc.
USA	Anaheim automation
USA	Arc System Inc.
Frg	Baumueller
Slovenia	Domel
USA	Emerson Electric Corporation
The states	General Electric
The states	Johnson Electric Holdings Limited
Germany	Liebherr
Switzerland	Maxon motor
Nippon	Nidec Corporation
Frg	Nord
U.s.	Regal Beloit Corporation
Federal republic of germany	Rexroth Bosch Grouping
Germany	Siemens AG
Brazil	WEG

References

GOST 27471-87 Rotating electrical machines. Terms and definitions.
I.V. Saveliev. The course of general physics, volume I. Mechanics, oscillations and waves, molecular physics.-Moscow: 1970.
IEC 38-83 Standard voltages.
GOST 16264.0-85 Low power electrical motors.
A.I.Voldek, 5.V.Popov. Electrical machines. Air conditioning machines: A textbook for universities.- St. petersburg.: 2007.
Paul Waide, Conrad U. Brunner. Energy-Efficiency Policy Opportunities for Electric Motor-Driven Systems. International Free energy Bureau Working Newspaper, Energy Efficiency Series.: Paris, 2011.
Dr. J. Merwerth. The hybrid-synchronous motorcar of the new BMW i3 & i8 challenges with electric traction drives for vehicles. BMW Group, Workshop Academy Lund: Lund, 2014.