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1. First, send the MTR 2.03.01C version to the customer. This version has an output calibration function.
2. Select the appropriate communication protocol and use RS232 or RS485 to connect the MTR to the UPS.
3. After the connection is successful, select "DetectAdjust-Mod Adjust" to calibrate the module; select "Cab Adjust" to calibrate the output of the cabinet.
4. When measuring the output voltage data, select the DC + AC mode to measure the DC component in the output. For the other measurement data, simply choose the corresponding mode.
5. Enter the actual measured data into the "Measure" column of the MTR software, and then 
click "Adjust" to complete the calibration.
Note:  When the calibration module outputs, it is necessary to measure and calibrate each individual module in sequence. Only after completing the separate measurements and calibrations of all modules can the modules be put into operation.

The logical steps for the check are as follows:

1.The SNMP card address cannot be found:
a. It might be that the SNMP card or the machine slot is damaged. You can verify this by repeatedly plugging and unplugging the SNMP card, replacing the machine slot, or updating with a new SNMP card.
b.Check if the network cable is in good condition
c.Check whether there are any issues with the rear connection of the SNMP card slot.
d.The fuse on the monitoring board is damaged. Use 232 to connect the MTR software to check if it works. If the connection is successful, it indicates that the fuse is in good condition. If it fails, it means the fuse is damaged.

2. If the SNMP card address can be found but communication still fails:
a.Check if there are any issues with the communication protocol, baud rate, etc. Try to make the computer network segment and the SNMP card network segment as consistent as possible.

 1. There are two triggering methods for UPS EPO, one is EPO button (local EPO) and the other is dry contact (remote EPO). You can first connect the UPS to the MTR software, enter the "Service Settings" to disable remote EPO, and observe if the device still experiences this phenomenon. If the device no longer experiences EPO triggering abnormalities, the dry contact board of the device needs to be replaced.

2. If the problem persists, it may be due to an abnormality in the circuit of the EPO button. Then disable the local EPO and observe the device's operation. This situation may be due to damage to the control board or monitoring board of the device.

It is recommended to start the UPS in the maintenance bypass mode, then switch back to the bypass mode, and finally switch back to the main circuit. In this way, the impact current generated during the startup of the transformer on the UPS can be reduced.

The troubleshooting steps are as follows:
1.   Check the Phase Loss Percentage Setting: Inspect the phase loss percentage setting in the power settings. The factory default is typically 70%. This alarm will trigger when the phase voltage drops below this set value.
2.  Check for Grid Voltage Fluctuations: Use a multimeter to measure the voltage between the input terminals of the circuit breaker Q1 and the neutral line. Observe if the voltage ever falls below 154V. If the voltage is below 154V, this indicates a grid fluctuation issue that needs to be addressed by the customer's facility team.
3.  Inspect Wiring on the Main Control Board: Power off the unit completely. Then, check the power detection wiring at port J31 on the main control board. Disconnect the terminal and check if the wiring connections are secure. Trace the wiring to check if the connections at the circuit breaker Q3 are loose and verify that the wire sequence is correct.
4.  Replace the Control Board: If all the above steps are checked and confirmed correct, but the issue persists, it will be necessary to replace the control board.

The troubleshooting steps are as follows:
1.  Check the Normally Open/Normally Closed Contact Settings: First, verify if the unit's contact settings are correct. Confirm the signal feedback terminal type of the fan using the wiring diagram, and ensure it matches the DI (Digital Input) settings. Correct any discrepancies if found. (This issue commonly occurs during initial startup or after fan maintenance.)
2.  Inspect the Signal Cable Connection: Check the signal cable connections. Ensure the fan's signal feedback terminal is connected to the controller's DI1 port and that the control signal has a 0-10V output. Verify all connections are secure without any looseness.
3.  Inspect the Power Cable Connection: Check the power cable connections. Confirm the fan's power cables are correctly and securely connected, with all terminals properly tightened.
4.  Replace the Fan: If all the above steps are confirmed correct and the issue persists, proceed to replace the fan.

GD350-19 is currently only supported for use in closed-loop control. The open-loop observer is unstable at low frequencies and not very reliable, so it is not recommended to use the locked-rotor protection in open-loop control.

Q1 : What is a sampling resistor circuit? What is its function in a UPS?
* Sampling resistor circuit:
A sampling resistor circuit , also known as a current sensing circuit, is a circuit that indirectly calculates the current flowing through a branch by measuring the voltage drop across a known resistance resistor.
-  Its core principle is based on Ohm's law: 
V = I × R
- Where: 
V is the voltage drop across the sensing resistor. 
I is the current flowing through the sensing resistor (which is the current we want to measure). 
R is the resistance of the sensing resistor. 
Since the resistance value R is known, as long as the voltage V across it is accurately measured, the current I = V / R can be easily calculated .

* The role of the sampling resistor circuit in a UPS:
1. System monitoring and status diagnosis 
2. Overcurrent and short circuit protection 
3. Closed-loop control 

* Sampling resistor circuit physical diagram and circuit diagram (Figure 1 is the physical diagram on the PCB board, and Figure 2 is its circuit diagram)

 Figure 1

Figure 2 

Q2: What fault information will the UPS report when the sampling resistor circuit fails/the current in a certain circuit is abnormal? 
A: The UPS will report ‘Bypass Volt Detect Fail-Set’ fault (as shown in Figure 3 below).

 Figure 3 

NOTE: The Figure shows '2# Bypass Volt Detect Fail-Set' fault, where 2# refers to module 2 and 0# to the bypass module. 

Q3: When the UPS reports ‘Bypass Volt Detect Fail-Set’ fault, what are the typical troubleshooting steps? 
A: When the sampling resistor circuit is faulty, the typical troubleshooting steps are as follows: 
1. Check the actual input/output values of the circuit based on the location of the fault; 
2. If the actual input/output values are normal, consider whether the detection circuit on the PCB board is faulty; (For modular UPS systems, first determine if the power module/bypass module detection circuit is faulty)

Q4: How to detect whether the sampling resistor circuit on the PCB board is faulty? 
A: The method for detecting a sampling resistor circuit fault is as follows: 
1. Locate the corresponding point on the PCB board; use the ohmmeter function (Ω) of a multimeter; touch the two points on the PCB board by the multimeter probes; check whether the resistance value is within the effective range (the deviations of resistance value will vary depending on the type of resistor) ; (The detection points are shown in Figure 4).

Figure 4

Q1: What alarms does the UPS typically display when the fan malfunctions? A: When the fan malfunctions, the UPS will typically display "Fan Fail-Set" (as shown in Figure 1 below).

Figure 1

NOTE: The Figure shows ‘0# Bypass Fan Fail Set’ fault, where ‘0#’ is the bypass module and ‘X#’ is module X.

Q2: What are the common causes when the UPS displays a "Fan Fail-Set" alarm?

A: The main causes of ‘Fan Fail-Set’ alarm on the UPS are as follows:
1) Fan/fan power cable failure
2) Fan signal cable failure (white signal cable from the fan power board to the fan)
3) Short-circuit function failure of the fan power board (the short-circuit point may vary depending on the model)
4) Fan power board failure
5) Auxiliary power board failure
6) Monitoring signal cable failure (signal cable from the monitoring board to the fan power board)
7) Monitoring board failure

Q3: What are the usual troubleshooting steps when the UPS displays 'Fan Fail-Set' alarm?
A: The usual troubleshooting steps when the UPS displays ‘Fan Fail-Set’ alarm are as follows:
1) Use a jumper cap to short-circuit the power signal interface of the fan power board, and test interfaces 1—n+1 in sequence.
If there are no alarms, it is normal. If there are alarms, the source of the fault needs to be identified. The source of the fault can be determined by replacing the fan or by interface testing (as shown in Figure 2).

Figure 2

2) If the source of the fault cannot be determined in the first step, continue to check:

① Fan power supply board:
J1: Fan PWM signal and LED indicators signal, power supply (as shown in Figure 3 below)

Figure 3

② Check if the auxiliary power board is faulty: If the power board is supplying power normally, its LED light will light up (as shown in Figure 4 below).

Figure 4

3) If the source of the fault cannot be determined in the second step, further checks are required:
① Replace the monitoring board
② Replace the cable connecting the monitoring board to the fan power board.