Motor protection · Selection guide

A practical guide to choosing the right PKZM family, setting motor overload protection, and checking short-circuit coordination and Type E requirements before ordering.

Eaton PKZM motor-protective circuit breakers combine motor overload protection and short-circuit protection in one device. The correct selection still depends on the exact subfamily, the motor nameplate, the prospective fault current and the approved combination of accessories.

• Start with the exact PKZM model—not just the family name.
• Set the overload release using the motor nameplate and the model instructions.
• Verify short-circuit ratings and Type E approvals for the complete combination.

Official Eaton product image · PKZM0 family · View product details

• What PKZM protects
• Compare PKZM families
• Set overload protection
• Check short-circuit protection
• Type E and combinations
• Selection checklist
• FAQ

1. What does a PKZM motor protector do?

A motor-protective circuit breaker combines two protective functions: a thermal overload release for sustained overcurrent and a magnetic or instantaneous release for short-circuit faults. This can reduce panel space and wiring compared with a separate overload relay plus a separate short-circuit protective device, but it does not remove the need to check the complete motor starter design.

Protection coordination still depends on the contactor, wiring, available fault current, starting conditions and the manufacturer’s tested combinations. Use the exact model’s datasheet and installation instructions when validating a design.

2. Start with the PKZM family and current range

These are family-level limits from Eaton product literature, not a substitute for checking the exact part number or regional catalogue. The family name alone does not specify the overload range, interrupting rating or accessory kit.

3. Set the overload release from the motor nameplate

The thermal overload setting should be selected from the motor’s rated current and the instructions for the specific protector and motor application. Do not use motor power alone as a substitute for the nameplate current when the nameplate is available.

• Read the motor full-load current at the actual supply voltage and connection.
• Confirm that the selected device’s adjustable range includes that current.
• Apply the motor manufacturer’s instructions and applicable installation rules.
• Check ambient temperature, enclosure conditions and any required derating.

Eaton lists phase-failure sensitivity for PKZM0 devices in its product information, but the precise characteristics and permitted applications must still be confirmed for the selected model.

4. Do not assume the short-circuit release is adjustable

The overload adjustment and the short-circuit release are different functions. Some PKZM models use a fixed instantaneous short-circuit release, while their overload release is adjustable within the range printed on the device or datasheet. For example, Eaton’s PKZM0-1-PI listing shows equal minimum and maximum values for its instantaneous short-circuit release, illustrating why the exact model data matters.

Before specifying the breaker, check:

• Rated operational voltage and short-circuit breaking capacity.
• Prospective short-circuit current at the installation point.
• Permitted upstream protective devices and coordination tables.
• Motor starting current and duration, so normal starting does not cause unwanted trips.

5. Type E and self-protected combinations

“Type E” is a specific combination-motor-controller classification used in North American applications; it should not be inferred from the PKZM family name alone. Check the exact breaker, terminal kit or accessory combination, voltage, available fault current and the applicable UL/CSA listing or manufacturer documentation.

6. PKZM selection checklist

1. Record motor nameplate current, voltage, phase and starting method.
2. Choose PKZM01, PKZM0 or PKZM4 according to the required current range and mounting.
3. Confirm the thermal adjustment range and the short-circuit release characteristics.
4. Check prospective fault current, interrupting capacity and coordination with the contactor and upstream protection.
5. Confirm accessories, terminal style, enclosure and any Type E or regional certification requirement.
6. Verify the complete order code against the current Eaton catalogue before purchase.

Frequently asked questions

Does a PKZM replace both an overload relay and a short-circuit protective device?

It combines overload and short-circuit protective functions in one device, but the complete starter still has to meet the applicable coordination, fault-current and installation requirements.

Can I use the same accessories on every PKZM model?

No. Accessory and terminal compatibility must be checked against the exact family and model. Eaton documentation may list shared accessories for specific groups, but do not assume universal fit.

Is the magnetic short-circuit setting adjustable?

Not on every model. Check the exact product data; some versions have a fixed instantaneous release.

• Eaton PKZM0-1-PI product page
• Eaton PKZM4-63/AK product page
• Eaton Switching and Protecting Motors catalogue

Always use the current regional datasheet and the exact catalog number for final engineering and purchasing decisions.