Type the marking as it reads on the label. Click a terminal in the diagram to see what its number says. Below the examples, an offered contactor can be checked against it: the category current, the coil, the auxiliary contacts and the insulation values.
On the labels alone: choosing a contactor for the motor and the circuit stays with the panel design.
Contactors in the starter panels of pumps, fans and compressors carry their ratings on the side label and their terminal numbers on the front: AC-3 9 A 400 V, Uc 230 V 50/60 Hz, A1 and A2, 13-14 and 21-22. Type what the label shows, and the reader names the utilization category to IEC 60947-4-1 or 60947-5-1, the rated values, the coil and the auxiliary contacts, explains each terminal number on a circuit diagram, checks an offered contactor and writes an RFQ line.
The current a contactor breaks in each category, its endurance and the makers’ type codes are not given here: they come from the maker’s catalogue.
AC-1 is a resistive load, AC-3 a squirrel-cage motor started and switched off running, AC-4 a motor that is also plugged and inched. A contactor carries its own current in each category, so a current says nothing without its category and voltage.
Ue and Ie: the operational voltage and current the category is given for. Ui: the insulation voltage. Uimp: the impulse voltage the insulation withstands. Ith: the thermal current in free air, Ithe in an enclosure. Uc: the coil (control supply) voltage.
A1 and A2 are the coil. 1/L1, 3/L2, 5/L3 take the supply and 2/T1, 4/T2, 6/T3 go to the load. An auxiliary contact has two digits: the first counts it in sequence, the second gives its function, 1-2 normally closed and 3-4 normally open; 5-6 and 7-8 are the same with a special function, such as the overload relay’s 95-96 and 97-98.
| Category | Standard | Typical load |
|---|---|---|
| AC-1 | IEC 60947-4-1 | Non-inductive or slightly inductive loads: resistance furnaces, heaters |
| AC-2 | IEC 60947-4-1 | Slip-ring motors: starting, switching off |
| AC-3 | IEC 60947-4-1 | Squirrel-cage motors: starting, switching off running motors |
| AC-3e | IEC 60947-4-1 | High-efficiency squirrel-cage motors with a higher locked-rotor current: starting, switching off running motors |
| AC-4 | IEC 60947-4-1 | Squirrel-cage motors: starting, plugging, inching |
| AC-5a | IEC 60947-4-1 | Switching of discharge lamps |
| AC-5b | IEC 60947-4-1 | Switching of incandescent lamps |
| AC-6a | IEC 60947-4-1 | Switching of transformers |
| AC-6b | IEC 60947-4-1 | Switching of capacitor banks |
| AC-8a | IEC 60947-4-1 | Hermetic refrigerant compressor motors, overload releases reset by hand |
| AC-8b | IEC 60947-4-1 | Hermetic refrigerant compressor motors, overload releases reset automatically |
| DC-1 | IEC 60947-4-1 | Non-inductive or slightly inductive loads: resistance furnaces |
| DC-3 | IEC 60947-4-1 | Shunt motors: starting, plugging, inching, dynamic braking |
| DC-5 | IEC 60947-4-1 | Series motors: starting, plugging, inching, dynamic braking |
| DC-6 | IEC 60947-4-1 | Switching of incandescent lamps |
| AC-12 | IEC 60947-5-1 | Control of resistive loads and solid-state loads with opto-coupler isolation |
| AC-13 | IEC 60947-5-1 | Control of solid-state loads with transformer isolation |
| AC-14 | IEC 60947-5-1 | Control of small electromagnetic loads, up to 72 VA |
| AC-15 | IEC 60947-5-1 | Control of AC electromagnetic loads over 72 VA |
| DC-12 | IEC 60947-5-1 | Control of resistive loads and solid-state loads with opto-coupler isolation |
| DC-13 | IEC 60947-5-1 | Control of DC electromagnets |
| DC-14 | IEC 60947-5-1 | Control of DC electromagnetic loads with economy resistors in the circuit |
| AC-20 | IEC 60947-3 | Connecting and disconnecting under no-load conditions (switch-disconnectors) |
| AC-21 | IEC 60947-3 | Switching of resistive loads, including moderate overloads (switch-disconnectors) |
| AC-22 | IEC 60947-3 | Switching of mixed resistive and inductive loads, including moderate overloads (switch-disconnectors) |
| AC-23 | IEC 60947-3 | Switching of motor loads or other highly inductive loads (switch-disconnectors) |
AC-7a and AC-7b (household appliances), the breaking-current multiples of each category and the meaning of the A or B after AC-20 to AC-23 are left out: only one of the sources gives them, or the sources differ. So are DC-20 to DC-23.
Utilization categories: the Wikipedia list of utilization categories and ABB’s motor protection and control catalogue; the 72 VA limit of AC-15: ABB’s catalogue and the Wikipedia article on contactors; the switch-disconnector categories AC-20 to AC-23 of IEC 60947-3: the same Wikipedia list and VIOX’s IEC 60947-3 guide. Terminal numbers: ABB’s terminal marking guide (IEC 60445, IEC 60947-1, EN 50005, EN 50012, EN 50011), Sprecher + Schuh’s note on CA7 auxiliary contacts (13-14 NO, 21-22 NC), Siemens SIRIUS auxiliary switches by sequence number, and the Siemens and ABB overload relay data (the NC contact drops the contactor, the NO contact signals the trip); auxiliary blocks 11 and 22, Ith and Ithe: Danfoss’s CI contactor data sheet. Overload relay trip classes 10, 20 and 30: ABB’s thermal overload relay sheet and a Schneider Electric standards answer on IEC 60947-4-1; class 10A: the same Schneider answer and a DigiKey article.
The contactor switches a squirrel-cage motor drawing 9 A at 400 V: it starts the motor and switches it off running. The same contactor is rated separately for other categories, such as AC-1 for a resistive load, so a current means little without its category and voltage.
A1 and A2 are the coil terminals. 13-14 is the first auxiliary contact, normally open; 21-22 the second, normally closed. The first digit counts the contact in sequence, the second gives its function: 1-2 normally closed, 3-4 normally open.
No. The coil must match the control supply in voltage and in AC or DC. The reader marks another coil as not meeting, and a coil for 50 or 60 Hz alone against a 50/60 Hz one as a point to check.
Its trip class to IEC 60947-4-1: at 7.2 times the setting current the relay trips within 4 to 10 seconds. Class 10A trips within 2 to 10 seconds, class 20 within 6 to 20 and class 30 within 9 to 30. The setting current is set on the dial within the relay’s setting range, such as 7–10 A.
The side label in full (each category with its current and voltage), the coil voltage with AC or DC and the frequency, the auxiliary contacts, the overload relay’s class and setting range if one is fitted, the maker and type, the quantity, and a photograph of the contactor in the panel.
A decoded marking is a cross-check, not a contactor selection. Attach photographs of the label and the front, and Vessel Core checks them before an offer goes back.
