MECH5125 Electric and Hybrid Drivetrain Engineering
Practical - Required for coursework assignment
Experimental analysis of the electric motor and spur gear efficiency
Introduction
Gears are widely used in many sectors and area very popular choice in automotive engineering. Its small size, ability to transfer significant power, and durability contribute to its widespread usage. As with all mechanical systems, gears also have losses associated with power transfer. Simple spur gear pair can have quite low efficiency. This experiment is using two electric DC motors to analyse the power transfer losses and spur gear efficiency. The underlying principle is to use one motor connected to the power supply to produce mechanical energy and another connected to the resistor as a generator. The difference between the power supplied and the power recovered at the resistor will determine the overall system efficiency. Now there are two motor/generator system configurations:
1. Direct connection between the motor and generator with the axial coupling.
2. Spur gear pairs the connection between the motor and generator.
To evaluate the efficiency of the gear pair, the difference inefficiency between configurations 1 and 2 has to be calculated taking into account the number of gear pairs used in configuration 2.
The experiment is available in two versions: remote and in the lab.
Remote experiment:
To access it, use the following link and login with your student ID number:https://leedsgryphonracing.com/gearlab You should be able to see the following interface:
After logging in, each session will take 5 minutes when you can activate the motors and collect the data. Make sure to collect a sufficient amount of data to calculate the average and estimate the standard deviation. Once the collection is complete, download the data as an Excel tab-separated text file.
In the lab experiment:
Connect the setup according to the diagram in Fig.1 and measure the following:
1. Using a directly connected motor and generator with jaw-type coupling (Fig.2), measure (in the remote version, switch on motor_3):
a. Supplied power (voltage and current) on the power supply displays.
b. Generated power (voltage and current) on the load of 8 Ω .
2. Using the spur gear configuration between the motor and generator (Fig.3) measure (in the remote version, switch on motor_1):
a. Supplied power (voltage and current) on the power supply displays.
b. Generated power (voltage and current) on the load of 8 Ω .
Health & Safety precautions:
• Do not touch any rotating components or live wires.
• Connect the wires before turning on the power supply.
• Do not exceed 12V on the power supply.
• Do not run the motors continuously for more than 30 seconds without a longer break of 5 minutes.
Calculations to complete:
1. Direct motor and generator connection:
a. Calculate the power used by a motor.
b. Calculate the power created by a generator.
c. Calculate the efficiency of the directly connected system.
2. Connection of motor and generator using 4 spur gears:
a. Calculate the power used by a motor.
b. Calculate the power created by a generator.
c. Calculate the efficiency of the system connected by gears.
3. Calculate the efficiency of a single pair of spur gears from the difference inefficiencies in configurations 1 and 2 and the number of gear pairs.
Conclusions: Comment on measurement accuracy, potential losses in power transmission, and spur gear power transfer efficiency.
Provide your answers as an appendix to the Coursework Assignment Report (no longer than 1 page).
Useful Formulas:
Power [W]= Voltage [V] x Current [A]; Efficiency = power transferred / power supplied
Measure noise in [dB], Measure rotational speed in rotations per minute [rpm].
Data:
Spur gears: m=1.5 mm, number of teeth=20
Electric Motors/Generators: Type: DC; Voltage: 12 V; Speed: 3500 rpm
Figure 1: Electric and mechanical connections diagram.
Figure 2: Direct motor and generator connection.
Figure 3: Connection of motor and generator using 4 spur gears.