Purpose

This article explains how to configure an External Power Manager (EPM), set inverter communication parameters, configure CT ratios and export limitations, and perform commissioning tests to ensure proper operation and safety.
PDF is attached at the bottom of the article

EPM Basic Configuration

EPM Address

• The EPM address should always be set to 1.

Inverter Quantity

• Configure the number of inverters connected to the EPM.
• Supported examples: 1, 2, or 3 inverters.

Transmit Setting

• Set Transmit = OFF.

Run Time

• Configure RUN = 3600.

Inverter Configuration

For each connected inverter, configure the following settings:

External EPM

Other EPM Settings

Apply these settings to every inverter connected to the EPM.

CT Ratio Configuration

The EPM operates with CTs that provide a 5A secondary current.

Example

If a CT is rated:

• 300/5A

Configure the EPM CT ratio as:

• 60/1

Calculation:

300 ÷ 5 = 60

Always ensure the CT ratio entered into the EPM matches the installed CT specification.

Export Limitation (Backflow Control)

The Backflow setting determines the maximum export power allowed by the grid operator.

Example

System configuration:

• 2 × 100 kW inverters
• Grid operator export limit: 60 kW

EPM Backflow setting:

+60000 W

This ensures the EPM restricts inverter output so export to the grid does not exceed the approved limit.

FailSafe Operation

If a CT clamp malfunction occurs, the EPM will automatically restrict inverter power output to approximately 50-60 W as a protective measure.

This behavior helps prevent uncontrolled export caused by incorrect current measurements.

Commissioning and Functional Testing

After configuration, perform the following tests.

1. CT FailSafe Test

1. Disconnect one CT clamp from the EPM.
2. Verify the EPM enters CT-Failsafe mode.

2. EPM Communication Failure Test

1. Disconnect the RS485 cable connected to the EPM.
2. Confirm the alarm RS485AllFail appears.
3. Verify all connected inverters reduce export to less than 100 W.

3. Individual Inverter Communication Test

1. Disconnect the RS485 cable at each inverter individually.
2. Verify the affected inverter enters Failsafe Mode.

4. EPM Limitation Test

1. Set the Backflow value to +500 W.
2. Confirm all inverters display LimByEPM.

CT Verification Procedure

The most important commissioning step is verifying CT orientation and measurements.

1. Turn off all inverters.
2. Measure current on each phase using an AMP clamp meter.
3. Compare the clamp meter reading with the value shown on the EPM.
4. Verify the readings match for each phase.

Active Power Check

• The active power value on each phase should be negative.
• If active power is positive, the CT is installed in the wrong direction and must be reversed.

Quick Checklist

Before leaving site, verify:

✅ EPM address set to 1
✅ Correct inverter quantity configured
✅ External EPM enabled on all inverters
✅ Internal EPM functions disabled
✅ CT ratio matches installed CTs
✅ Export limit (Backflow) configured correctly
✅ CT-Failsafe test passed
✅ RS485 communication test passed
✅ LimByEPM test passed
✅ EPM current readings match clamp meter readings
✅ Active power is negative on all phases

This procedure ensures correct EPM operation, export limitation compliance, and proper failsafe protection