In the engineering practice of frequency converter drive systems, motor overheating protection is a key link to ensure equipment safety and continuous operation. Traditional thermal relays or bimetallic switches only provide simple switch protection, while temperature monitoring based on PTC thermistors can achieve more accurate and configurable temperature warning and fault response. The Bonfiglioli Vectron ACTION and ACTION Cube series frequency converters integrate a dedicated PTC thermistor input port through the EM-IO-02 expansion module, providing standard I/O expansion and CAN system bus communication, making motor temperature monitoring a standardized and parameterized system function.
This article is based on the EM-IO-02 extension module technical manual, providing a systematic technical operation guide for the core concerns of on-site engineers in installation, wiring, system bus configuration, and parameterization of motor temperature monitoring.
Overview and Functional Positioning of EM-IO-02 Expansion Module
1.1 Module Core Functions
EM-IO-02 is an optional hardware expansion component designed by Bonfiglioli Vectron for the ACTION and ACTION Cube series frequency converters, supporting software versions 4.1.0 and higher for the ACTION series and all ACU series devices. This module achieves the following functional extensions by inserting it into the lower expansion slot of the frequency converter:
CAN system bus interface: compliant with ISO-DIS 11898 (CAN High Speed) standard, supporting a maximum communication rate of 1 MBaud
Second bipolar analog input: 12 bit resolution, configurable for ± 10V voltage or ± 20mA current input
Second bipolar analog output: ± 10V voltage output, overload and short circuit protection
Three channel digital input: PLC compatible, 24V level, supports up to 150kHz frequency signal, can be used as speed sensor input
One way relay output: normally open contact, 24V AC/DC, 1A (resistive load)
PTC thermistor input: compliant with DIN 44081 standard, rated response resistance value of 2.85k Ω
1.2 Functional differences between EM-IO-01 and EM-IO-02
Compared with EM-IO-01, the core differentiating function of EM-IO-02 lies in motor PTC temperature monitoring:
Functional Comparison EM-IO-01 EM-IO-02
CAN system bus support
Analog input 1 channel (12 bits) 1 channel (12 bits)
Analog output 1 channel (± 10V) 1 channel (± 10V)
Digital input with 3 channels and 3 channels
Relay output 2 channels and 1 channel
PTC temperature input not supported (X410B. 1-2)
Key points of mechanical and electrical installation
2.1 Mechanical Installation
The mechanical installation steps of EM-IO-02 are exactly the same as those of EM-IO-01:
Power off confirmation: The frequency converter must be completely powered off and wait for the DC bus capacitor to discharge completely (several minutes).
Disassemble the lower cover plate: Remove the plastic cover plate on the lower part of the frequency converter.
Insertion module: Align the EM-IO-02 expansion module with the slot and apply even force to insert it, taking care to only hold the housing and avoid contact with the PCB.
Reset cover plate: Reinstall the lower cover plate.
2.2 Electrical Connections - Detailed Explanation of Terminal Definitions
EM-IO-02 provides two sockets: X410A and X410B.
Socket X410A (terminals 1-7):
Technical parameter description of terminal signal
1 20V output Imax=180mA to power external sensors
2 20V ground - corresponding to terminal 1 ground
3-digit input 1 (EM-S1IND) Umax=30V, 10mA@24V Response time is about 16ms
4-digit input 2 (EM-S2IND) can be used as the speed sensor Track A as above
5 digital inputs 3 (EM-S3IND) can be used as the speed sensor Track B as above
6-7 relay output (EM-S1OUTD) 24V AC/DC, 1A normally open contact
Socket X410B (terminals 1-7) - The PTC interface is located in this socket:
Technical parameter description of terminal signal
1-2 PTC Input (EM-MPTC) Rated Response Resistance 2.85k Ω (DIN 44081) Motor Temperature Monitoring
3 analog inputs (EM-S1INA) ± 10V/± 20mA, 12 bit second channel analog input
4 Analog Output (EM-S1OUTA) ± 10V, Imax=2mA Second Analog Output
5 CAN_Low - System Bus CAN Low Line
6 CAN-High - System Bus CAN High Line
7 CAN_SND - System Bus Ground
Key tip: Terminal X410B. 1-2 is a dedicated PTC thermistor input port that can be connected to PTC sensors or bimetallic temperature sensors (normally closed contacts) that comply with DIN 44081 standards.
2.3 Analog input voltage/current mode switching
The dip switch S3 on the module is used to configure the analog input signal type:
S3=OFF (right side): Voltage signal (± 10V)
S3=ON (left side): Current signal (± 20mA)
S1 and S2 switches are used for configuring the terminal resistance of the system bus (see System Bus chapter for details).
PTC Motor Temperature Monitoring - Detailed Explanation of Core Functions
3.1 Working principle of PTC monitoring
The resistance of PTC (Positive Temperature Coefficient) thermistor increases sharply with increasing temperature. When the temperature of the motor winding exceeds the rated threshold (usually 130 ° C~180 ° C, depending on the insulation level of the motor), the PTC resistor jumps from several hundred ohms to several thousand ohms. The frequency converter detects this change in resistance and triggers a warning or fault shutdown.
The PTC input port of EM-IO-02 is equipped with an evaluation circuit that complies with DIN 44081 standard, with a rated response resistance of 2.85k Ω, and can be directly connected to standard motor PTC sensors.
3.2 Operation mode of PTC monitoring (parameter 570)
EM-IO-02 extends the operating modes of the "Motor Temperature" section of the frequency converter, providing the following 5 new modes (selected through parameter 570 (Operation Mode Motor Temp.)):
Operating Mode Function Description Application Scenarios
Only display a warning when the threshold is exceeded, without triggering a shutdown
When the fault shutdown exceeds the threshold, immediately report fault F0400 and stop freely
13 fault shutdown, delayed for 1 minute, exceeded the threshold for 1 minute before reporting fault shutdown
14 fault shutdown, delayed for 5 minutes, exceeded the threshold for 5 minutes before reporting fault shutdown
15 fault shutdown, delayed for 10 minutes, exceeding the threshold for 10 minutes before reporting fault shutdown
The application value of delay mode: In some process scenarios, it is normal for the motor to overheat for a short time (such as during the start-up phase). Using delay shutdown can avoid unnecessary production interruptions and ensure that protection is ultimately triggered when the overheating continues.
3.3 PTC fault handling and confirmation
Fault code: F0400
Display mode: Operation unit KP500 displays "FAULT F0400"
Confirmation method: Fault confirmation is performed through parameter 34 (Program) or a digital input signal linked to parameter 103 (Error Acknowledgment)
Independent of controller enable: PTC monitoring function is independent of the running/stopping state of the frequency converter, and temperature monitoring continues to work even when the frequency converter is in a stopped state.
3.4 Temperature measurement through analog input
In addition to PTC switch monitoring, EM-IO-02 also supports continuous temperature measurement through analog input EM-S1INA (mode 2, parameter 465):
Temperature range: 0 ° C~200 ° C
Signal mapping: 0 ° C corresponds to 0V/0mA, 200 ° C corresponds to 10V/20mA
Application scenario: Connect an external temperature transmitter (such as PT100 transmitter) to achieve full temperature monitoring throughout the process

CAN system bus configuration
The system bus function of EM-IO-02 is completely consistent with EM-IO-01, both based on the CANopen protocol framework (CiA DS 301). The following are the key configuration points.
4.1 Terminal resistor configuration (dip switch S1/S2)
Bus physical head and tail nodes must be set with terminal resistors:
Passive terminal (S1=ON, S2=OFF): Conventional terminal matching
Active terminal (S1=ON, S2=ON): Improve the shape of CAN signal edges
Factory default: S1 and S2 are both OFF
4.2 Node ID and Baud Rate
Parameter Description Range Factory Value
900 Node-ID-1~63-1 (disabled)
903 Baud-Rate 3~8(50~1000 kBaud) —
Node ID setting rules:
-1: System bus disabled
0: Defined as the main station (only one is allowed)
1~63: Slave station address
4.3 Network Management State Machine
CANopen standard state management:
Pre Operational: Only SDO communication is allowed
Operational: Both SDO and PDO are allowed
Stopped: All communication is prohibited
The master station switches the slave station to Operational state through the NMT command "Start Remote Node" (command code=1). After initialization is completed, the main station periodically sends startup commands with a delay time set by parameter 904 (Boot Up Delay).
4.4 Emergency Response of the Main Station (Parameter 989)
Mode function
0-Error: When receiving an emergency message from the slave station, the master station stops simultaneously and reports F21nn (nn is the hexadecimal base of the slave station Node ID)
1- No Error only displays warning Sysbus (0x2000), the main station continues to run
4.5 Virtual Links
EM-IO-02 supports horizontal data transmission between frequency converters through TxPDO/RXPDO. Each TxPDO can transmit 8 bytes of data and supports three data types: Boolean, Word (2 bytes), and Long (4 bytes):
TxPDO channel Boolean byte parameters Word byte parameters Long byte parameters
TxPDO1 946~949 950~953 954~955
TxPDO2 956~959 960~963 964~965
TxPDO3 966~969 972~975 976~977
Example of Source Number:
Boolean source: 740=control word, 161=running status
Word source: 9063=percentage reference value 1
Long source: 900=output frequency, 62=reference frequency value
Key points of analog/digital I/O configuration
5.1 Analog input characteristic curve
The analog input of EM-IO-02 supports flexible mapping through two-point linear characteristic curves (parameters 564~567):
Parameter Description Range Factory Value
564 characteristic point X1-1000.00%~100.00% -98.00%
565 characteristic point Y1-1000.00%~100.00% -1000.00%
566 characteristic point X2-1000.00%~100.00% 98.00%
567 characteristic point Y2-1000.00%~100.00% 100.00%
Operation mode (parameter 562):
1. Bipolar: Complete mapping according to characteristic points
11- Unipolar: Mapping negative X-axis value to reference value 0
21- Monopolar 2... 10V/4... 20mA: Input range limited to 20%~100%
101- Bipolar absolute value: negative Y-axis value mapped to positive reference value
Tolerance band (parameter 560): used to expand the zero crossing range of the reference value, avoiding frequent switching of rotation direction near zero, with a range of 0.00%~25.00% and a factory value of 2.00%.
5.2 Digital input as speed sensor
The three-way digital input can be configured as an incremental speed sensor interface through parameter 493:
Mode 4- Quadruple Frequency Evaluation: Dual channel speed sensor with 4 edge evaluations per turn
Mode 104- Four fold Reverse: Speed value is reversed
Mode 1004/1104- with reference pulse: adding reference pulse for sensor monitoring
Index mark (parameter 494): range 1~8192, factory value 1024. The maximum division mark is determined by the maximum frequency limit of the digital input (150kHz).
Actual speed source selection (parameter 766): 1=speed sensor 1 (body), 2=speed sensor 2 (EM-IO-02).
5.3 Fixed frequency extension
EM-IO-02 expands the fixed frequency to 8 groups through parameter 131 (Fixed frequency change over 3):
Fixed frequency parameter FF3=0 FF3=1
Fixed frequency 5 485 0 1
Fixed frequency 6 486 1 1
Fixed frequency 7 487 1 0
Fixed frequency 8 488 0 1
Quick Reference Table for Fault Codes
Fault code description and troubleshooting suggestions
F0400 motor PTC temperature over limit inspection motor load, cooling conditions, and PTC sensor wiring
F1402 Analog Input EM-S1INA Signal Fault Check Signal Source and Wiring
F30 speed sensor 2 signal fault check sensor wiring and power supply
F31 speed sensor 2 phase loss signal check whether the A or B phase signal is lost
F32 Speed Sensor 2 Direction Error Check A/B Reverse Connection or Parameter Setting
F21nn system bus slave station fault check corresponding node status and communication link
F2200 SYNC message timeout check whether the SYNC generation of the main station is normal
F2201~03 RxPDO1-3 timeout check corresponding to the TxPDO configuration of the sending node
F2210 CAN bus BUS-OFF check for physical connections, terminal resistance, and baud rate
Bus load planning reference
System bus capacity planning is crucial for reliable communication. PDO message transmission time at different baud rates:
Baud rate (kBaud) message transmission time (μ s)
1000 140
500 280
250 560
125 1120
100 1400
50 2800
Bus load assessment criteria:
≤ 80%: Normal
80%~90%: critical
90%: unacceptable
