Electric motor nameplate
- Hz (Hertz). Hertz is used to measure frequency of cycles per second.
- KW (kilowatts). We use kilowatts to know the power.
- A (Amperage). Amperage indicates ampere consumption.
- Rpm (revolutions per minute). Speed at which the shaft rotates.
- V (Voltage). Working voltage which can be 230V or 420V.
- Cosφ (power factor). The power factor is represented by the cosine of fi.
In this case the number of hertz is 50Hz or 60Hz, that means that the motor supports 50 or 60 cycles per second depending of electricity supply, this electric motor has a power of 2.2 kilowatts and with a supply voltage of 230 volts we will have to connect in delta, if the supply voltage is 380 or 400 volts we will connect it in star. The current measured in amps is 8.38 amps if it’s connected to a 230 volts in delta, and 4.84 amps if it’s connected to a 400 volts in star. The consumption in amperes that the nameplate tells us is the nominal consumption of the motor. Finally the cosφ (power factor) is a constant and indicates the relationship between apparent power and active power.
1-Hz = Hertz
Hertz represents the frequency with which a cycle of an electromagnetic sine wave is repeated in a time period of one second.
In the case of the motor nameplate above, we have power, amperage, voltage, frequency, etc. The frequency is given by the electrical supply. An electrical supply with a frequency of 50 Hz or 60 Hz will directly affect the speed of the rotor. The equations that represents the value of the frequency is:
f = Frequency
T = time (Planck unit)
Hz = Hertz
s = seconds
A frequency of 50 Hz means that the sine wave of the electric current in each second repeats 50 wave cycles.
2-KW = Kilowatts, electric motor power
A watt is the unit of measure of power in the international system of units.
To name the power of the electric motors is used kilowatt (KW) or electrical horsepower, its equivalence is:
Hoursepower (HP)=746 Watts (W)
The equation that tells us the power that has a three-phase AC motor is as follows:
P = Power.
V = Voltage.
I = Intensity.
cosφ =Power factor.
3-A = Ampere (Intensity)
The ampere is the unit of measurement to know the current or electric current.
The law of Ohm is the equation that relates the intensity, resistance and voltage of an electric charge.
I = Intensity (Ampere).
V = Voltage.
R = Resistance (Ohms)
The equation that relates the power, voltage and current for an AC motor is:
We will know one of the ways of measuring the consumption of a motor with the aid of an amperimetric clamp.
In order to be able to measure the amperage of consumption of a motor we will place one of the phases inside the amperometric clamp, and the selector of the amperometric clamp we will place it in A. (amperage), depending on the work of the motor the consumption that will measure us the clamp will generally be higher at the start and then lower to obtain its nominal consumption.
At start motor can consume up to 5 times its rated current during the time it takes to stabilize, typically about 5 seconds.
4-rpm = revolutions per minute, speed of electric motors
The rpm tells us how often the rotor of an electric motor rotates in a minute, the equation for measuring this rotational speed of the rotor of an electric motor can be expressed as follows:
5-V = Voltage
Connection to the motor terminals.
A three-phase AC electric motor can be connected in star or delta, depending on the winding characteristics of the motor.
On the nameplate of a motor, the working voltage is shown as 220, 230, 380, 400, 690. Seeing the following nameplates, we will connect a three-phase AC motor as follows:
In the case of the above image the connection will be made in delta because the mains voltage we have is 400V and the wiring of the coils of this motor is with a mains voltage of 400V in delta and with a mains voltage of 690V in star.
In the case of the above image the connection will be made in star because the mains voltage is 400V and the connection of the coils of this motor is with a mains voltage of 400V in star and with a mains voltage of 230V in delta.
6-cosφ =Power factor
cosφ = (P)/(√(P2 + Q2))
Where we can define:
cosφ = cosine of fi (power factor).
P = Active power.
Q = Reactive power.
To understand what the power factor is, it is very useful to talk about the power triangle:
S = Apparent power (kVA).
P = Active power (kW).
Q = Reactive power (kVAR).
V = Voltage (V).
I = Intensity (A).
φ = Angle of the triangle that forms the edges of apparent power and active power.
In other words, the power factor is the ratio between the actual power of the work and the actual power consumed, so when the power factor gets closer to 1, more efficient will be the motor in relation to the energy consumption.
This video explains how works the induction motor
This video seems very interesting to know how the electric motor works:
Parts of an electric motor
The main parts are the flange, this part is located in front or below and is for to fix the motor to the piece that we want to move. The housing, is the motor body, in the central part, where the stator is housed. The stator is made up of the motor winding. The rotor is located inside the stator and is responsible for moving the motor shaft through magnetic currents produced in the stator. The junction box is where we will connect the power wirings. The cover is located at the rear and is for to cover the cooling fan of the motor. The nameplate usually located on the side and indicates some technical data of the operation of the motor.