Cam Switches Selection Guide
Cam switches are switches whose position is selected by turning the handle; on-off, step, reversing, star-delta and Dahlander types are chosen by the job.
This guide explains what to look at when choosing products in the Cam Switches category.
Cam switch types
- On-Off Switches: main and local switches with 0-1 positions; besides one-, two- and three-phase models, four-, five- and six-pole ones are also listed.
- Step Switches: select steps in sequence as the handle is turned; used for switching between transformer winding taps and heater groups. Options such as 3, 5, 7 and 10 steps are available; standard, mains and selector types are in separate subgroups.
- Pole-Changing Reversing Switches: a pole-changing switch transfers the load between two circuits (1-0-2); a reversing (forward-reverse) switch changes the direction of rotation of a motor.
- Star-Delta Switches: connect a three-phase motor first in star, then in delta; Opaş also lists types with the 0 position in the middle ("center-0").
- Two-Speed Dahlander Switches: select the speed on two-speed motors with a Dahlander winding; in these motors the number of poles changes in a 1:2 ratio and the speed in a 2:1 ratio.
- Gas-Shielded Welding Machine Switches: 3-, 7- and 10-step switches for selecting the steps of a welding machine.
- Cam Switch Accessories and Spare Parts: plastic switch enclosures for on-off, reversing and star-delta switches.
How to read the product name
- Number of phases: in Metop and Opaş names, "phase" is the number of poles the switch switches at the same time; a "six-phase" switch has six poles.
- Continuously rotating: the sequence of positions repeats through the turn; on a Metop Dahlander switch the sequence is written as 0-1-2-0-1-2-0.
- Enclosed: the switch comes in its own enclosure, ready for surface mounting. Models without an enclosure are fitted to a panel door or a machine body.
- Series in parentheses: the expressions "M40 Standard Series" and "TR40 Terminal Connected" in Opaş names distinguish different series and connection types at the same current.
What to look at when choosing
- Contact diagram. When replacing a faulty switch, look not only at the name but at the number of positions, the handle angle and the terminal numbers of the old switch; on switches that do the same job, the terminal layout varies from manufacturer to manufacturer.
- Current and load type. The current in the product name is not valid for every load; for a switch that will directly switch a motor on and off, use the current or power value the manufacturer gives for motor loads.
- Number of poles. Chosen according to the number of conductors to be switched; in three-phase circuits where the neutral will also be cut, a three-phase + neutral or four-pole model is needed.
- Mounting. For a switch to be fitted to a panel door, the front frame size determines the layout; for a surface-mounted switch, the enclosure size does.
The difference between a cam switch and contactor control
A cam switch keeps its position mechanically. When power is cut and comes back, the motor fed by a switch left in the run position starts again. On machines where automatic restart is not wanted, control is built through a contactor or a motor protection circuit breaker with an undervoltage coil is used. With a star-delta cam switch, the operator determines the moment of changeover from star to delta; where the changeover must be time-based and automatic, a contactor star-delta starter is preferred; these products are listed in the Motor Control Equipment category. For transfer between the mains and a generator there is also the Transfer Switches category.
Brands in this category
- Metop: present in all subgroups; mini, enclosed and continuously rotating models, as well as Dahlander, gas-shielded welding machine, mains and selector step switches and switch enclosures, are from this brand.
- Opaş: on-off, step, pole-changing and star-delta switches; the product name states the 66x66 or 90x90 frame size and the series.
- Schneider Electric: cam switches with K1, K2, K30, K50 and K63 codes.
Order notes
Cam switches are sold by the piece. Most of the products are lead-time items; the delivery time is confirmed before the order is placed. You can search for Metop and Opaş products by current and type name, and for Schneider Electric cam switches by manufacturer code such as K1B002ALH. If the enclosure is bought separately, the enclosure's current rating and switch type (on-off, reversing, star-delta) must be the same as the switch's.
Rotary cam switch comparison table
| Cam Switch Function | Poles / Steps | Typical Current | Application Scenario | Category Link |
|---|---|---|---|---|
| On-Off (0-1) cam switch | 1P – 6P | 16 A – 200 A | Machine main isolation and door-interlocked panel switching | On-Off Cam Switches |
| Changeover / reversing (1-0-2) | 1P – 6P | 16 A – 200 A | Manual mains-generator transfer and motor direction reversal | Changeover Switches |
| Multi-step cam switch | 2 – 10 steps | 16 A – 125 A | Heater stage selection, fan speed control, and tap switching | Step Cam Switches |
| Voltmeter / ammeter selector | 3-phase measurement | 10 A – 25 A | Monitoring L1-L2-L3 phase voltages or currents on a single meter | Commutator Switches |
Frequently asked questions
How does a reversing cam switch work?
A reversing (forward-reverse) switch has a 0 position in the middle and one operating position on each side. On a three-phase motor, in one position it connects the phases directly, and in the other it swaps two phases; the motor then turns in the opposite direction. The motor is expected to stop before the direction is changed; applying reverse to a rotating motor is a heavy duty condition defined by a separate utilization category (AC-4). Separate reversing models are listed for single-phase motors.
Which should be chosen, a pole-changing switch with 0 or without 0?
In the model with 0 (1-0-2), there is an off position between the two positions in which the load is connected to neither circuit; the switch also serves as an on-off switch. In the model without 0, the load is always connected to one of the two circuits, and switching off is done with another switch. If the load needs to be left unpowered on site, the model with 0 is chosen. Verify from the manufacturer's contact diagram how the contacts behave during the changeover.
Can a star-delta cam switch be used with every motor?
No. The six winding ends of the motor must be brought out to the terminal box, and the motor must be suitable for delta-connected operation at the mains voltage; the voltage and connection information on the nameplate shows this. By turning the switch, the motor is connected first in star, then in delta, and the operator determines the moment of changeover. If the changeover is wanted to be timed and automatic, a contactor star-delta starter is used. Overload and short-circuit protection is installed separately.
Does the current written on a cam switch also apply to a motor?
Not always. IEC 60947-3, which covers cam switches, defines a switch's current together with the utilization category: AC-21 is for resistive loads, AC-22 for mixed resistive and inductive loads, and AC-23 for motors and highly inductive loads. The rated current of the same switch under a motor load is generally lower than under a resistive load. For a switch that will directly switch a motor on and off, use the current or motor power value the manufacturer gives for the AC-23 or AC-3 category.
Which motors is a Dahlander switch used with?
It is used with two-speed Dahlander motors, whose single winding can be connected for two different numbers of poles. In these motors the number of poles changes in a 1:2 ratio and the speed in a 2:1 ratio; in the constant-torque type the winding is connected in delta at low speed and in double star at high speed, and the motor has six connection terminals. The switch changes between these two connections with positions 0, 1 and 2. Two-speed motors with two separate windings require a different diagram; check the motor nameplate.