Eaton PKZM0 Motor Protector Sizing: Complete B2B Selection Flowchart

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“name”: “Step 1: Identify the motor nameplate full-load current (FLC)”,
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“text”: “Read the FLC directly from the motor nameplate. This is the value the PKZM0 is set to (not the nameplate kW — converting kW to FLC requires assumptions about efficiency and power factor that introduce error).”
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“name”: “Step 2: Choose the PKZM0 range that includes the FLC”,
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“text”: “For a 4 kW motor at 400 V with FLC 8.5 A, the PKZM0-10 (range 6.3 – 10 A) is the right choice. Set the rotary adjustment to 8.5 A.”
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“name”: “Step 3: Verify the motor starting current”,
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“text”: “For direct-on-line starting, the motor inrush is typically 6 to 8 × FLC. The PKZM0’s instantaneous magnetic trip is set at approximately 12 × the maximum of the current range, so a PKZM0-10 trips magnetically at ~120 A — well above the motor inrush of 8.5 A × 8 = 68 A. No nuisance trip.”
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“name”: “Step 4: Verify the short-circuit current at the installation point”,
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“text”: “The PKZM0 has a short-circuit breaking capacity of 50 kA at 400 V. For installations with prospective short-circuit current below 50 kA, the PKZM0 provides full protection. For higher fault currents, use an upstream NZM molded case circuit breaker for back-up protection.”
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“name”: “Step 5: Choose a compatible contactor”,
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“text”: “The PKZM0 connects mechanically to a DILM contactor of the same frame. Common pairings: PKZM0-0,4 → DILM7-10 (up to 4 kW) PKZM0-4 → DILM9-10 (up to 4 kW) PKZM0-10 → DILM17-10 (up to 7.5 kW) PKZM0-16 → DILM25-10 (up to 11 kW) PKZM0-25 → DILM32-XSP (up to 15 kW)”
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“text”: “Common PKZM0 accessories for B2B projects: PKZM0-XC45 — top-hat rail adapter for 45 mm DIN rail PKZM0-XMR — shunt release (for remote tripping) PKZM0-XDM12-PI — three-phase wiring module for line-side connection PKZM0-XSPI32 — spring clamp terminal adapter For a full accessories list, see the PKZM0 product catalog .”
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“name”: “Example 1: Conveyor motor, 2.2 kW at 400 V”,
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“text”: “FLC = 5 A, motor inrush = 35 A, prospective short-circuit = 10 kA. Choose PKZM0-6,3 (range 4 – 6.3 A) set to 5 A. Pair with DILM9-10 contactor.”
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“name”: “Example 2: Pump motor, 7.5 kW at 400 V”,
“acceptedAnswer”: {
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“text”: “FLC = 14 A, motor inrush = 100 A, prospective short-circuit = 25 kA. Choose PKZM0-16 (range 10 – 16 A) set to 14 A. Pair with DILM25-10 contactor.”
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“acceptedAnswer”: {
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“text”: “FLC = 21 A, motor inrush = 150 A, prospective short-circuit = 35 kA. Choose PKZM0-25 (range 20 – 25 A) set to 21 A. Pair with DILM32-XSP contactor. Add PKZM0-XMR shunt release for fire alarm integration.”
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“text”: “Yes — with the PKZM0-XMR shunt release, a remote trip signal (24 Vdc, 110 Vac, or 230 Vac) can open the breaker. The reset is still local.”
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The Eaton Moeller PKZM0 is one of the most widely used motor-protective circuit breakers in industrial control panels. Combining a rotary switch, thermal overload, and short-circuit protection in a single 45 mm DIN-rail device, the PKZM0 saves panel space and simplifies wiring compared to a traditional fuse + contactor + thermal overload arrangement.

This B2B selection guide covers the practical sizing workflow for the PKZM0: how to choose the correct current setting, how to match it with the downstream contactor and motor, and when to use the PKZM0 versus the more advanced PKE electronic version.

1. Why B2B Buyers Choose PKZM0 Over Fuse + Contactor + Overload

For motor branch circuits up to 25 A (approximately 11 kW at 400 V), the Eaton PKZM0 replaces a traditional three-component protection scheme with a single device. The benefits for B2B panel builders:

Space savings — one DIN-rail module replaces fuse holder + contactor + overload relay, typically cutting panel width by 50%.
Wiring simplification — single line-of-power wiring instead of three separate circuits.
Restart advantage — after a trip, the operator simply resets the rotary switch. No fuse replacement required.
Visible isolation — the rotary handle provides visible lockout-tagout, satisfying IEC 60204-1 safety requirements.

For OEM machine builders producing hundreds of units per year, the panel space and wiring labor savings are substantial.

2. PKZM0 Current Range and Catalog Numbers

The PKZM0 family covers motor FLC from 0.1 A to 25 A, with seven adjustable ranges:

Catalog Number	Current Range	Typical 400 V Motor Power
PKZM0-0,4	0.25 – 0.4 A	0.09 kW
PKZM0-1	0.63 – 1.0 A	0.25 kW
PKZM0-1,6	1.0 – 1.6 A	0.55 kW
PKZM0-2,5	1.6 – 2.5 A	0.75 kW
PKZM0-4	2.5 – 4.0 A	1.5 kW
PKZM0-6,3	4.0 – 6.3 A	2.2 kW
PKZM0-10	6.3 – 10 A	4 kW
PKZM0-12	9.0 – 12 A	5.5 kW
PKZM0-16	10 – 16 A	7.5 kW
PKZM0-20	16 – 20 A	9 kW
PKZM0-25	20 – 25 A	11 kW

For motors above 25 A, the Eaton PKZM4 (32 A to 65 A range) or PKZM01-XRM12-PI / XRM32-PI modules with separate current transformers are used. For most B2B machine-building applications under 11 kW, the standard PKZM0 is the right choice.

3. PKZM0 Sizing Flowchart

Follow this six-step process to size a PKZM0 correctly for any B2B motor circuit:

Step 1: Identify the motor nameplate full-load current (FLC)

Read the FLC directly from the motor nameplate. This is the value the PKZM0 is set to (not the nameplate kW — converting kW to FLC requires assumptions about efficiency and power factor that introduce error).

Step 2: Choose the PKZM0 range that includes the FLC

For a 4 kW motor at 400 V with FLC 8.5 A, the PKZM0-10 (range 6.3 – 10 A) is the right choice. Set the rotary adjustment to 8.5 A.

Step 3: Verify the motor starting current

For direct-on-line starting, the motor inrush is typically 6 to 8 × FLC. The PKZM0’s instantaneous magnetic trip is set at approximately 12 × the maximum of the current range, so a PKZM0-10 trips magnetically at ~120 A — well above the motor inrush of 8.5 A × 8 = 68 A. No nuisance trip.

Step 4: Verify the short-circuit current at the installation point

The PKZM0 has a short-circuit breaking capacity of 50 kA at 400 V. For installations with prospective short-circuit current below 50 kA, the PKZM0 provides full protection. For higher fault currents, use an upstream NZM molded case circuit breaker for back-up protection.

Step 5: Choose a compatible contactor

The PKZM0 connects mechanically to a DILM contactor of the same frame. Common pairings:

PKZM0-0,4 → DILM7-10 (up to 4 kW)
PKZM0-4 → DILM9-10 (up to 4 kW)
PKZM0-10 → DILM17-10 (up to 7.5 kW)
PKZM0-16 → DILM25-10 (up to 11 kW)
PKZM0-25 → DILM32-XSP (up to 15 kW)

Step 6: Add accessories as required

Common PKZM0 accessories for B2B projects:

PKZM0-XC45 — top-hat rail adapter for 45 mm DIN rail
PKZM0-XMR — shunt release (for remote tripping)
PKZM0-XDM12-PI — three-phase wiring module for line-side connection
PKZM0-XSPI32 — spring clamp terminal adapter

For a full accessories list, see the PKZM0 product catalog.

4. PKZM0 vs PKE: When to Use Electronic Protection

For motors above 11 kW, or for applications requiring more sophisticated protection (phase loss, phase sequence, undercurrent, electronic trip logging), the Eaton PKE is the next step up. Comparison:

Feature	PKZM0	PKE
Trip type	Thermal-magnetic (bimetal)	Electronic (microprocessor)
Current range	0.1 – 25 A	0.3 – 65 A
Adjustability	Rotary dial (mechanical)	Push-button (digital)
Phase loss protection	Yes (inherent)	Yes (inherent)
Communication	No	Yes (PKE-SWD modules)
Cost	Lower	Higher

For a 15 kW motor, B2B buyers usually choose either the PKZM4 (32 A range) or the PKE12 (electronic). The decision is based on whether the application needs the PKE’s electronic features (communication, electronic trip logging).

5. PKZM0 Trip Curves and Class

The PKZM0 is a Class 10 thermal overload — meaning it will trip in 10 seconds or less at 7.2 × the FLC setting. This is suitable for normal motor starting applications. For heavy-duty starting (high inertia loads, long acceleration times), the Class 20 or Class 30 versions are available, but the PKZM0 family is primarily Class 10.

6. Common B2B Sizing Examples

Example 1: Conveyor motor, 2.2 kW at 400 V

FLC = 5 A, motor inrush = 35 A, prospective short-circuit = 10 kA. Choose PKZM0-6,3 (range 4 – 6.3 A) set to 5 A. Pair with DILM9-10 contactor.

Example 2: Pump motor, 7.5 kW at 400 V

FLC = 14 A, motor inrush = 100 A, prospective short-circuit = 25 kA. Choose PKZM0-16 (range 10 – 16 A) set to 14 A. Pair with DILM25-10 contactor.

Example 3: HVAC fan motor, 11 kW at 400 V

FLC = 21 A, motor inrush = 150 A, prospective short-circuit = 35 kA. Choose PKZM0-25 (range 20 – 25 A) set to 21 A. Pair with DILM32-XSP contactor. Add PKZM0-XMR shunt release for fire alarm integration.

7. Frequently Asked Questions

Can the PKZM0 be used for single-phase motors?

Yes — connect two of the three poles in series, or use the single-pole variant. For 3-phase motors, use the standard 3-pole PKZM0.

What is the difference between PKZM0 and PKZM01?

PKZM01 is the same as PKZM0 — they are the same product family. The naming convention is interchangeable in some regional catalogs.

Can the PKZM0 be reset remotely?

Yes — with the PKZM0-XMR shunt release, a remote trip signal (24 Vdc, 110 Vac, or 230 Vac) can open the breaker. The reset is still local.

Is the PKZM0 approved for DC motor applications?

Yes, but with limitations. The PKZM0 is rated for DC applications up to 250 V DC per pole, and the short-circuit breaking capacity is lower than AC. For higher DC voltages, use a dedicated DC-rated device.

Conclusion

The Eaton PKZM0 motor protector is a workhorse device for B2B motor branch circuits up to 25 A. By following the selection workflow — read the motor FLC, choose the matching PKZM0 range, verify the inrush and short-circuit conditions, and pair with the correct contactor — B2B panel builders can deliver reliable motor control in a compact DIN-rail footprint.

For project quotations, technical datasheets, or B2B volume pricing on the Eaton Moeller PKZM0 family, contact our team or browse the full PKZM0 product catalog online.