How Can I Test Relay Outputs on a PowerFlex 75X 22 Series I/O Module?
Programming and testing relay outputs on PowerFlex 750 drives with 22 series drive option I/O card.
PowerFlex 750-Series drives can use 22-Series I/O option modules to provide additional analog and discrete I/O. Depending on the module selected, the discrete inputs may operate at 24V DC or 120V AC.
The process for configuring the module's relay outputs is the same regardless of the I/O voltage.
Relay outputs can be configured to change state based on drive conditions such as:
- Drive Running
- Drive Faulted
- At Speed
- Drive Ready
- Direction
- At Reference
- Alarm conditions
- Other available drive or option-module status bits
The relay outputs are dry contacts. They do not provide control voltage themselves.
Identify the I/O Module Port
Before programming the relay output, determine which device port contains the 22-Series I/O module.
For example, if the I/O module is installed in Port 4, its parameters will appear under Port 4.
Throughout this article, Port nn refers to the port containing the I/O module.
Relay Output Selection
Each relay output has a selection parameter that determines what condition will control the relay.
Relay Output 0
Port nn:10 [R00 Sel]
Relay Output 1
Port nn:20 [R01 Sel]
These parameters allow the relay to be linked to a specific parameter and bit within the drive.
When the selected bit is TRUE, the relay energizes.
When the selected bit is FALSE, the relay de-energizes.
Configuring a Relay Output
To configure a relay:
- Navigate to the port containing the 22-Series I/O module.
- Open the relay selection parameter:nn:10 [R00 Sel] for Relay Output 0ornn:20 [R01 Sel] for Relay Output 1.
- Select the drive parameter containing the desired status.
- Select the individual bit corresponding to the condition that should operate the relay.
- Apply/save the parameter change.
The relay will now follow the selected status bit.
Example – Relay Operates When the Drive Faults
Suppose Relay Output 0 needs to indicate that the drive is faulted.
Navigate to:
Port nn:10 [R00 Sel]
Select:
Port 0:935 [Drive Status 1]
Then select:
Bit 7 – Faulted
The resulting operation is:
Drive not faulted → Relay de-energized
Drive faulted → Relay energized
If the external circuit is connected through the relay's Normally Open (NO) contact, the circuit closes when the drive faults.
If it is connected through the Normally Closed (NC) contact, the circuit opens when the drive faults.
Adding ON/OFF Delays
Each relay output also has configurable ON and OFF delays.
Relay Output 0
nn:14 [R00 On Time]
nn:15 [R00 Off Time]
Relay Output 1
nn:24 [R01 On Time]
nn:25 [R01 Off Time]
The ON Time determines how long the selected condition must remain TRUE before the relay energizes.
The OFF Time determines how long the relay remains energized after the selected condition becomes FALSE.
For immediate operation, leave these parameters at 0.0 seconds.
Verifying Relay Operation
The commanded state of the relay outputs can be viewed using:
Port nn:5 [Dig Out Sts]
This parameter allows the relay state to be checked from the drive without immediately troubleshooting the external wiring.
If the appropriate bit in [Dig Out Sts] changes state when the selected condition occurs, the drive is commanding the output correctly.
If the drive indicates that the relay is energized but the connected device does not change state, check:
- External control voltage
- Relay common wiring
- NO/NC terminal selection
- Field wiring
- Connected device
- Relay contact/load ratings
If [Dig Out Sts] does not change state, verify the source parameter and bit selected in [R00 Sel] or [R01 Sel].
Relay Output Wiring
The relay outputs are dry contacts.
A typical relay provides:
- C – Common
- NO – Normally Open
- NC – Normally Closed
An external control voltage must be supplied to the relay common.
For example:
Control Voltage → Relay Common
Relay NO → Controlled Device
Controlled Device → Control Common/Return
When the programmed drive condition becomes TRUE, the relay energizes and the NO contact closes.
Always verify the allowable voltage and current ratings of the specific 22-Series I/O module before connecting a load.
Troubleshooting
When a relay output is not operating as expected, troubleshoot in the following order:
- Verify the correct 22-Series I/O module port.
- Verify [R00 Sel] or [R01 Sel] points to the intended parameter and bit.
- Verify that the selected drive-status bit actually changes state.
- Check nn:5 [Dig Out Sts] to determine whether the drive is commanding the relay.
- Verify the external control voltage and field wiring.
- Verify that the correct NO or NC contact is being used.
- Verify that the connected load is within the relay contact ratings.
This process helps determine whether the issue is with the drive configuration, I/O module, or external wiring.
Key Parameters
| Function | Parameter |
|---|---|
| Relay Output 0 Selection | nn:10 [R00 Sel] |
| Relay Output 0 ON Delay | nn:14 [R00 On Time] |
| Relay Output 0 OFF Delay | nn:15 [R00 Off Time] |
| Relay Output 1 Selection | nn:20 [R01 Sel] |
| Relay Output 1 ON Delay | nn:24 [R01 On Time] |
| Relay Output 1 OFF Delay | nn:25 [R01 Off Time] |
| Digital Output Status | nn:5 [Dig Out Sts] |
nn = Device port containing the 22-Series I/O module
References
Rockwell Automation Publication 750-PM001 – PowerFlex 750-Series AC Drives Programming Manual
Rockwell Automation PowerFlex 750-Series I/O, Feedback, and Power Option Module Installation Instructions