On a SINAMICS G120 the terminals are on the control unit, not the power module. A CU240E-2 provides six digital inputs, two analogue inputs, two analogue outputs, digital outputs including a relay, an internal 24 V supply and the Safe Torque Off terminals. What each terminal does is not fixed by the hardware — it is decided by the macro parameter p0015, which pre-assigns every input and output in one step. Verify your wiring with the read-only parameters: r0722 shows digital input status bit by bit, and r0755 shows the scaled analogue input value. Those two parameters answer almost every "is my wiring right?" question.
- Choose the macro first, then wire to match it. Wiring first and forcing the macro afterwards means re-assigning terminals by hand.
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r0722is the fastest wiring check there is — toggle a switch, watch the bit. - The internal 24 V supply is convenient but limited. Check the current budget before powering external sensors from it.
- Safe Torque Off terminals must be supplied with 24 V or the drive will not run, and the fault message rarely points at them clearly.
The Terminal Strip at a Glance
A G120 is two units bolted together: a power module carrying line and motor connections, and a control unit carrying every control signal. All of the terminals discussed here are on the control unit, which is why plugging a commissioning cable into the power module finds nothing.
| Group | On a CU240E-2 | Typical use |
|---|---|---|
| Digital inputs | DI 0 to DI 5 | Start, stop, direction, fixed-speed selection, external fault, acknowledge |
| Digital input common | DI COM terminals | Sets sink or source operation for the input group |
| Analogue inputs | AI 0 and AI 1 | Speed reference from a potentiometer, PLC or transmitter |
| Analogue outputs | AO 0 and AO 1 | Speed or current signal to a panel meter or PLC input |
| Digital outputs | Relay and transistor outputs | Fault, alarm, running indication, brake control |
| Internal supply | 24 V and 0 V terminals | Powering the digital inputs and small external devices |
| Safety | STO input terminals | Safe Torque Off from a safety relay |
Terminal numbering differs between control unit variants — a CU240B-2 has fewer inputs and no relay output. Always work from the terminal diagram for the exact control unit in front of you rather than from a generic drawing.
Digital Inputs and the Sink/Source Decision
The digital inputs can operate in either direction, decided by how the common terminal is wired.
| Mode | Wiring | An input is active when |
|---|---|---|
| Source (PNP) | DI COM linked to 0 V | 24 V is switched onto the input terminal |
| Sink (NPN) | DI COM linked to 24 V | The input terminal is pulled down to 0 V |
Source operation is the usual choice in most installations and matches the majority of PLC digital outputs. What matters is consistency: the whole input group shares one common, so you cannot mix source and sink signals on the same control unit.
If the drive has been wired by someone else and inputs behave inversely — the motor runs when the switch is open — check the common before suspecting the parameters. That symptom is almost always a sink/source mismatch.
When powering the inputs from the drive's own 24 V supply, keep the load within the published limit. It is intended for the drive's own inputs and a small number of external contacts, not for a panel full of sensors.
Wire a real drive, then prove it works
Hands-on SINAMICS G120 terminal wiring, macro selection and verification on live hardware — Pune or online.
Analogue Inputs and Outputs
Each analogue input accepts either a voltage or a current signal, and this is set in two places that must agree: a DIP switch on the control unit selects the hardware mode, and p0756 tells the firmware which type to expect.
| Signal | DIP switch | Typical p0756 setting | Notes |
|---|---|---|---|
| 0 to 10 V | Voltage position | Unipolar voltage | Simple; more susceptible to noise in a drive panel |
| 0 to 20 mA | Current position | Unipolar current | Better noise immunity, no wire-break detection |
| 4 to 20 mA | Current position | Unipolar current with monitoring | Preferred — a broken wire reads 0 mA and is detectable |
The switch-and-parameter pairing is a classic commissioning trap. A 4–20 mA transmitter wired to an input whose DIP switch is still in the voltage position produces a reading that never moves, and no fault appears — the drive is simply measuring a voltage that is not there.
Use 4–20 mA wherever the choice exists. The live zero means a broken wire reads as 0 mA and can be trapped as a fault, whereas a broken 0–10 V wire reads as a perfectly valid zero-speed command.
The analogue outputs work the same way in reverse and are commonly assigned to actual speed and actual current, feeding a panel meter or a PLC analogue input on installations without a fieldbus.
Digital Outputs and the Relay
Digital outputs are assigned through the p073x parameter group — p0730 for DO 0, p0731 for DO 1, p0732 for DO 2 on control units that have them. Each is set to a binector, meaning an internal status bit.
| Common assignment | Signals |
|---|---|
| Fault active | The drive has tripped — the most common relay assignment |
| Operation enabled | Motor genuinely running, suitable for a panel lamp or PLC input |
| Alarm active | A warning condition that does not stop the drive |
| Motor holding brake | Brake release control on hoist and vertical applications |
The relay output is the one to use for anything that must be reported when the drive itself is unhealthy, since it is a physical contact rather than a transistor referenced to the drive's own supply.
How p0015 Decides What Each Terminal Does
None of these terminals has a fixed function. p0015 selects a macro — a pre-built assignment of every digital and analogue terminal for a common application pattern — and applying it rewrites the underlying BICO interconnections in one step.
| Macro | Interface pattern |
|---|---|
| 1 | Two fixed speeds |
| 3 | Four fixed speeds |
| 12 | Two-wire control with analogue setpoint on AI 0 |
| 17, 18 | Two-wire control, methods 2 and 3 |
| 19, 20 | Three-wire control, methods 1 and 2 |
| 21 | Fieldbus USS |
Macro availability varies by control unit, so check the list for your specific CU rather than assuming. The practical sequence is: choose the macro that best fits the application, wire the terminal strip to match it, set it during basic commissioning, and only then adjust individual terminals that do not suit.
Doing it the other way round — wiring first and then hunting for a macro that fits — usually ends with manual BICO re-assignment of several terminals, which is harder to hand over and easy to lose if the macro is ever re-applied.
Reading Terminal State from Parameters
Two read-only parameters turn wiring verification from guesswork into a two-minute check.
r0722 shows the status of every digital input as individual bits — bit 0 is DI 0, bit 1 is DI 1, and so on. Toggle a switch and watch the bit change. If the bit does not move, the problem is wiring, the common, or the supply, and no amount of parameter work will fix it.
r0755 shows the scaled analogue input value as a percentage. Turn a potentiometer and watch it sweep. If it sits at zero or at a fixed value, check the DIP switch and p0756 before anything else.
Prove every terminal this way before commissioning the drive properly. Five minutes with these two parameters removes wiring from the list of suspects for the rest of the job.
Step-by-Step Lab: Wire and Verify Every Terminal
Hands-on- A G120 with a CU240E-2 or similar control unit on a training rig, safely isolated for wiring.
- A few toggle switches or pushbuttons, a 10 kΩ potentiometer, and the terminal diagram for your exact control unit.
- Estimated time: 45 minutes.
Identify the control unit and find its diagram
Read the type designation from the control unit label and locate the matching terminal diagram. Do not work from a generic drawing.
Set the input common for source operation
With the drive isolated, link DI COM to 0 V, then wire switches from 24 V into DI 0, DI 1 and DI 2.
Verify with r0722 before doing anything else
Power up and display r0722. Toggle each switch in turn and watch the corresponding bit.
Wire the potentiometer and set the input type
Wire the potentiometer across the 10 V reference and 0 V with the wiper to AI 0. Set the DIP switch to voltage and p0756 to unipolar voltage.
Sweep the analogue input
Display r0755 and turn the potentiometer through its full range.
Assign the relay and prove it
Set p0730 to the fault binector, then provoke a fault and listen for the relay.
Watch a macro rewrite your work
Note which terminals do what, then change p0015 to a different macro and check r0722 behaviour again.
The wiring is proven when every digital input moves its bit in r0722, the analogue input sweeps the full range in r0755, and the relay follows the fault state. Do this before commissioning any drive and wiring stops being a suspect for the rest of the job.
Frequently asked questions
Where are the control terminals on a SINAMICS G120?
On the control unit, not the power module. The power module carries only line and motor connections. A CU240E-2 provides six digital inputs, two analogue inputs, two analogue outputs, digital and relay outputs, an internal 24 V supply and the Safe Torque Off terminals.
How do I check whether my digital input wiring is correct?
Display r0722, which shows each digital input as an individual bit, and toggle the switch. If the bit does not follow, the fault is in the wiring, the common connection or the supply — not in the parameters.
What is the difference between sink and source wiring?
In source operation the common is linked to 0 V and an input is active when 24 V is applied to it. In sink operation the common is linked to 24 V and an input is active when pulled to 0 V. The whole input group shares one common, so the two cannot be mixed on one control unit.
Why does my analogue input read nothing?
Most often the DIP switch and p0756 disagree — for example a 4–20 mA transmitter wired to an input still switched to voltage mode. Both the hardware switch and the parameter must match the signal type. Verify with r0755.
Should I use 0–10 V or 4–20 mA for the speed reference?
Prefer 4–20 mA. Current loops resist the electrical noise present in a drive panel far better, and the live zero means a broken wire reads as 0 mA and can be trapped as a fault, whereas a broken 0–10 V wire reads as a valid zero-speed command.
Why did my terminal functions change by themselves?
The macro parameter p0015 was almost certainly changed. A macro re-assigns every digital and analogue terminal in one step by rewriting the underlying interconnections. Choose the macro first, then wire to match it.