What Is a CPS? The All-in-One Motor Starter (Control & Protective Switching)
Quick answer: A CPS (Control & Protective Switching device) is an all-in-one motor starter that combines what normally takes three separate devices — a contactor, an overload relay, and short-circuit protection — into a single compact unit. CNC's YCKB7 covers up to 63 A. It saves panel space, cuts wiring, and gives a motor coordinated protection out of the box. Here's what a CPS is, when to choose one over the traditional contactor-plus-relay approach, and where it fits.
The standard way to start and protect a motor uses a chain of separate parts: a breaker or fuse for short-circuit protection, a contactor to switch the motor on and off, and an overload relay to trip if the motor draws too much current for too long. It works — but it's three devices, three sets of terminals, and a fair amount of panel space and wiring. A Control & Protective Switching device rolls all three jobs into one integrated unit, and that's the whole point of it.
What a CPS actually is
A CPS is a single device that provides, in one housing:
- Switching — turning the motor on and off (the contactor's job).
- Overload protection — tripping when the motor runs overloaded (the overload relay's job).
- Short-circuit protection — disconnecting instantly on a fault (the breaker/fuse's job).
Because these functions are engineered together, they're already coordinated — the manufacturer has matched the switching, overload and short-circuit elements so they work as one. With a traditional contactor-plus-relay-plus-breaker setup, achieving proper coordination is on the panel designer; with a CPS, it comes built in.
CPS vs the traditional contactor + overload relay + breaker
| Aspect | CPS (YCKB7) | Contactor + relay + breaker |
|---|---|---|
| Devices | One integrated unit | Three separate components |
| Panel space | Compact | Larger footprint |
| Wiring | Less — pre-linked internally | More interconnections to make |
| Coordination | Built in by the maker | Designer must match components |
| Flexibility | Fixed function set | Mix and match / replace parts individually |
The trade-off is flexibility: with separate parts you can swap a single failed component or reconfigure the protection. A CPS is a sealed, coordinated package — simpler and more compact, but a single unit. For a lot of standard motor feeders, that simplicity is exactly what you want.
When to choose a CPS
- Panel space is tight — the integrated unit frees up DIN rail versus three separate devices.
- You want guaranteed coordination without designing it yourself.
- You're building many identical motor feeders — a CPS standardises each one and cuts assembly time.
- You want fewer connections to fail or maintain.
If instead you need to start a large motor gently to protect the machinery and the supply, that's a different requirement — a soft starter or a VFD handles the starting method, while a CPS handles the switch-and-protect function for direct-on-line feeders.
The YCKB7
CNC's YCKB7 is an integrated CPS rated up to 63 A, provided across a range of current settings to match different motor sizes. It gives switching, overload and short-circuit protection in one coordinated device for direct motor feeders — the compact, pre-coordinated alternative to assembling a contactor, overload relay and breaker separately. For the exact current setting to match your motor, send us the motor's full-load current and we'll confirm the model.
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Frequently asked questions
What is a CPS (control and protective switching device)?
It's an all-in-one motor starter that combines switching (contactor), overload protection (overload relay) and short-circuit protection (breaker/fuse) into a single coordinated unit, saving space and wiring.
How is a CPS different from a contactor?
A contactor only switches the circuit on and off. A CPS includes that switching plus the overload and short-circuit protection a motor needs — so one CPS replaces a contactor, an overload relay and a breaker together.
Does a CPS replace the overload relay and breaker?
Yes — that's the point of it. The overload and short-circuit functions are built in and pre-coordinated with the switching, so you don't fit a separate overload relay or motor breaker alongside it.
When should I use a CPS instead of separate components?
Choose a CPS when panel space is tight, when you want guaranteed coordination without designing it, or when you're building many identical motor feeders and want to standardise and speed up assembly. Choose separate components when you need to reconfigure or replace individual parts.
Does a CPS start a motor softly?
No — a CPS switches a motor direct-on-line and protects it, but it doesn't reduce starting current. If you need a gentle start, use a soft starter or a VFD, which control the starting method; a CPS handles switch-and-protect.
What size CPS do I need?
Match it to the motor's full-load current so the overload element is set correctly. The YCKB7 is offered across current settings up to 63 A. Send us the motor nameplate current and we'll confirm the right one.
Related
This guide is general information for Pakistani installations. Final device selection, current setting and coordination should be confirmed by a qualified electrician for your motor and supply.
Deciding between a CPS and a traditional contactor-plus-relay setup? CNC Electric is the authorised CNC distributor in Pakistan — message us on WhatsApp with your motor details and we'll recommend the right approach.