Week 17 : Solving the Timeout Error

 We check our coding and we quickly realize that the VI in the red box is causing the timeout error. The function of this VI is to configure current range for a specific test. This is part of the forever loop for power meter in which it keeps on acquiring the V,A,W readings at high speed. After it finishes 1 iteration, it will configure the current range again until the program stop. Hence, we put this VI outside the forever loop so that it only run once.



As we thought the problem has been resolved, this is what we get when we execute the program, an unknown error. Despite this error, our program has made some improvement over the timeout error. The program don't crash that often, sometimes it executes without crashing in the whole test which is around 4 minutes. We are close to solve this error.

Week 16 : A New Problem Emerged

 In order to increase the speed of our program, we introduce a Run (Waveform) button in the oscilloscope program. Our program will only capture the waveform and autosets it to the best voltage vs time when the button is pressed.

The same modification goes to Agilent Technologies 34980A. This is because when all the instruments run together at the same time, the program will become very slow. This will jeopardize the whole test as the readings from the power meter will not be real time, it will update once almost every 8 seconds which is unacceptable.The power meter is crucial for both Open Circuit and Short Circuit tests, the 3 phase voltages has to be set within the range states in ATP. If the voltages are too much out of range, it will cause the ATU/GATU to overheat and thus damage the units.

 

Upon successfully communicate with the power supply and acquire data at real time for power meter, a new problem emerged which is shown as above.This is a timeout error when the instruments may not respond rapidly to commands written to the port, causing a large delay between VISA Write and VISA Read. This means that our program crashes when it is half way executed, when it crashes it will stop communicating with all the instruments that are using GPIB-USB cable.

Hence a Wait function between VISA Write and Read to effectively avoid a potential timeout error.

 

We add in the wait function for the power supply as well as power meter, however the program still crash. We suspect the power meter is causing the error because it is always the first one to crash.. Furthermore the test bench is occupied so we are unable to carry out investigation of the problem. We hope to resolve this by next week.

Week 15 : Success in Controlling MX45-3Pi Power Supply

 We manage to solve all the problems we encounter last week with the new driver from CAPRA bench. These are the VIs necessary for our programming.

This is an example of CONFIGURE ALL VOLTAGE VI, the string INST:COUP ALL is required to control all the 3 phase voltages together. We were unable to access the low level VI previously but with this new driver we are able to access and modify low level VI within the driver.

 This VI is used to control the slew rate of all 3 phase voltages.

We configure the voltage slew rate to 20V/s for safety purposes. When we  enable the output it will delay for 0.5s before ramp up the 3 phase voltages from 0 to 235V with a rate of 20V/s . Case structure is used to select the value of output voltage automatically when the users selects the program.

This portion enables the power supply to reduce to all the 3 phase voltages to 0V and disable the output automatically. In order to ramp down the voltage to 0V in exact time, we create 2 local variables: #3 VOLTAGE 1 OUTPUT LIMIT (from the diagram below) & RATE (3rd diagram) and change it to read. After that we use  #3 divide by RATE  and plus 1.5 to get the total delay time before disabling the output so that the voltage can reach 0V before the output is being disabled.

After that we combine our power supply software with the 3 instruments software for testing, the results are shown below :

Note: The above result is not from the latest program. We have finish our main program and will test it out when the bench is available.

Setting up GATU :

Week 14: Design of Ramp Up/Down Voltage and Troubleshooting

 

These are the problems we encounter when we program the slew rate for power supply :

1. All the 3 phase voltages are unable to respond at the same time.
2. Users have to press the "UPDATE" button 3 times to increase/decrease all the 3 phase voltages.
3. A specific amount of delay time must be introduced so that the slew rate work perfectly.
4. It will increase/decrease the voltage phase by phase which is undesirable
5. The built file cannot be executed on the other computer

 All these problems are caused by the driver we downloaded from the 3rd party website, which is the California Instrument, Ametek Programmable Power website as LabView doesn't develop this driver. It's tough for us to troubleshoot the problem as the test bench is always in used, hence it is time consuming for us to solve the problem. However we are closed to solving the problems above.

 

Our task this week is to configure the power supply so that it will increase the voltage slowly to 235V with a slew rate of 20V/s. We have faced a lot of problems with this features.

At first, we program it in such a way that  it enables the output first before load in the voltage value. However this cause the output ramp up phase by phase which is undesirable.

The main culprit of the fault is time. The value must be loaded into the VI before enabling the output so that all the 3 phase voltages can ramp up together. However, this leads to another problem which is all the 3 phase voltages ramp down phase by phase with a great amount of delay in between it.

We are still troubleshooting the problem and try to solve it by next week.

Week 13 : Configuration of Voltage Range

 

The default program for power supply - Voltage Range 150 V.

•  For ATU/GATU , we need to supply 235 V to each phase. With the Voltage Range 150V is being set by default, the max voltage can only supply up to 150V. 

• Hence, we are required to configure the VOLTAGE RANGE to 300V.

 

This is the VI  that we use to configure the VOLTAGE RANGE.

 

This is how we connect the VI in the program to improve on it. 

 

 After we set the VOLTAGE RANGE to 300 V, the power supply put itself into HI RANGE mode which will activate its RELAY internally to support the flow of high voltage.

• The switching of the RELAY produces tremendous noise which interfere the communication and data acquisition between each instruments and therefore interrupt the program.

• Therefore, we decided to use this FLAT SEQUENCE STRUCTURE to arrange the flow of each part of programs.

• We arranged the program of power supply in the SEQUENCE 1,so that when the program runs,it will first finish initializing the power supply and switching of relay to HI RANGE, then only start to initialize other 3 instruments.

• In between, we added in some buffer time before the program start to initialize the 3 instruments.It is 5 seconds.

• Below is the VI and how we connect the TIME DELAY in the program.

Week 12 : Execute Button

                                  

 

We have improved our front panel appearance for power supply as shown in the diagram above.

• As for safety purposes,we added in one EXECUTE BUTTON for each of the programs to prevent some careless mistakes make by operators such as typo like 235 V to 2350 V.

•  With this EXECUTE BUTTON, it acts like ENTER,every time after we edit the voltage level for each phase,it is necessary for us to press the button to call out the voltage from power supply.  

Here is the example of careless mistake might make by the operators - accidentally set the voltage to  2350 V. 

• With the absence of EXECUTE BUTTON, the power supply will directly supply 2350 V which causes overheating and damage to the power supply.

• Besides, we added in the VOLTAGE OUTPUT LIMIT at the right side to have double safety protection.We set the maximum voltage output limit to 270 V.

 

This is how the EXECUTE BUTTON"s block diagram looks like.We put it into a event structure so that the program will wait for user to press the button first, then only it will load the voltage.

 

For every EXECUTE BUTTONS , we set their MECHANICAL ACTION to LATCH.

When the user press the button, it executes, the green light indicator lights on, until it finish executing,the indicator lights off.

Week 11 : Design of California MX45 - 3Pi Power Supply

At first we are asked to program the Pacific Power Source but that model is the only power supply in Singapore. Therefore we change from Pacific Power Source to California Power Supply, which the company has 2 units.

 
The way we program the California Power Supply is similar with the Pacific Power Source.

 These are the VIs we use to program the California Power Supply.

This is the front panel of our program. First select the Program you want (the programs are arranged according to Acceptance Test Procedure), after that press the OUTPUT DISABLE BUTTON so that it becomes green colour OUTPUT ENABLE.
 After that the voltage and frequency can be control through the blue box above. We'd also set the max voltage limit to 350V and current limit to 40A.

 For example, if we select program 4, the gauge will display the program that is in action and the tab control will switch to program 4 automatically.

Due to some issues with the driver, we can only run this program in the desktop with LabView installed. We are asked to solve this problem so that this program can be run in the ELS desktop too.