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Check Engine Power Without Nameplate: Measuring Old Attic Engine's Power Capacity

Mixerios 28974 38
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How can I estimate the power of an old electric motor without its nameplate?

You usually cannot determine the exact power from the missing nameplate alone, but you can estimate it from photos and motor dimensions. Measure the shaft diameter and the housing/core dimensions (A/B/D/E, AC, H) or, better, the inner core diameter and core length; with those values the motor can often be identified or narrowed down to a specific model [#16940410] [#16940473] [#18995168] [#18995223] The thread also notes that four-pole motors like these are typically around 1440 rpm, so speed can be inferred from the motor type if the model is known [#18995223] For similar SZJd/SZJe motors, people in the thread estimated anything from about 2.2 kW to 5.5 kW depending on size, and one example was identified as an SZJe 34a with 3 kW, 1430 rpm, and 6.5 A at 380 V star connection [#16940548] [#16940745] [#16940755] [#18995244]
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  • #1 16940345
    Mixerios
    Level 7  
    Posts: 83
    Rate: 13
    Hello, I found an old engine in the attic. Unfortunately, without the nameplate, and here my question appears: Is it possible to check the engine power without this nameplate?

    Thank you in advance for your help.
    greetings
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  • #2 16940354
    sp3ots
    Level 38  
    Posts: 3065
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    Hello.
    Show engine.
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  • #3 16940410
    Krzysztof Reszka
    VIP Meritorious for electroda.pl  
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    Mixerios wrote:
    Hello, I found an old engine in the attic. Unfortunately, without the nameplate and here comes my question: Is it possible to check the engine power without this plate?

    It can be roughly stated if it is not an unusual motor, and three-phase or single-phase. Please give photos of the engine.
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  • #4 16940473
    Rezystor240
    Level 42  
    Posts: 9240
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    Mixerios wrote:
    Is it possible to check the engine power without this plate?


    Measure the diameter of the motor shaft.
  • #6 16940548
    Rezystor240
    Level 42  
    Posts: 9240
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    @Mixerios

    I think the power is about 5.5kW.
    I can be wrong, these are just my passages.
  • #7 16940611
    rafcio_21
    Level 29  
    Posts: 1110
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    I would bet that it has about 4 kW of similar size I have in a made compressor.
  • #8 16940745
    krzysiek7
    Moderator of Electricians group  
    Posts: 4835
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    Rate: 1910
    Polish SZJd engine ....... It can have a maximum of 2.8 kW, depending on its rotational speed.
  • #9 16940755
    Tomasz Downacki
    Level 13  
    Posts: 125
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    No more than 3kW.
  • #10 16940954
    Krzysztof Reszka
    VIP Meritorious for electroda.pl  
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    Will we guess that?
    Please enter dimensions.
    A / B / D / E.
    Check Engine Power Without Nameplate: Measuring Old Attic Engine's Power Capacity
  • #11 17034056
    xdawidek05
    Level 1  
    Posts: 1
    Rate: 3
    Hello, I have a similar problem. I have a motor that is without a nameplate:
    Check Engine Power Without Nameplate: Measuring Old Attic Engine's Power Capacity Check Engine Power Without Nameplate: Measuring Old Attic Engine's Power Capacity Check Engine Power Without Nameplate: Measuring Old Attic Engine's Power Capacity Check Engine Power Without Nameplate: Measuring Old Attic Engine's Power Capacity

    Will anyone be able to determine the parameters of this engine (power, rotational speed)?
    What dimensions do I need to provide? (according to the drawing from the previous post)
  • #12 18994579
    Szmajdek
    Level 6  
    Posts: 6
    Rate: 3
    Hello. I will not start a new thread because I have a similar problem. I found my grandfather krajzege in the garage and he wants to reactivate it. Referring to the scheme as above
    A - 115
    B-190
    D-28/30
    E-60
    Check Engine Power Without Nameplate: Measuring Old Attic Engine's Power Capacity
    Check Engine Power Without Nameplate: Measuring Old Attic Engine's Power Capacity
    The cable is also "tired" so I will replace it but I do not know what square is there and what to replace it. 4-wire 3-phase motor.
  • #13 18994628
    sp3ots
    Level 38  
    Posts: 3065
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    Hello !
    Szmajdek wrote:
    Hello. I will not start a new thread because I have a similar problem. I found my grandfather krajzege in the garage and he wants to reactivate it. Referring to the scheme as above

    ........................
    Check Engine Power Without Nameplate: Measuring Old Attic Engine's Power Capacity
    The cable is also "tired" so I will replace it but I do not know what square is there and what to replace it. 4-wire 3-phase motor.


    The engine shown in the photo is damaged (burnt).
    Do not connect it to electricity /
  • #14 18995106
    Szmajdek
    Level 6  
    Posts: 6
    Rate: 3
    The engine worked until I unscrewed it and opened it ...
  • #15 18995168
    Łukasz.K
    Level 28  
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    The power can be determined on the basis of the H dimension, i.e. the shaft shear. With a high probability, it is an engine for about 1440 rpm. The rotational speed can be determined by connecting to the network whether it spins fast or slow. And the diameter of the shaft also proves its power as well as the length of the stator, i.e. generally and the motor, i.e. L.

    Added after 2 [minutes]:

    Due to the small size E and dimensions A and B, I would say that it is a low power engine of 2.2kW.

    Added after 1 [minutes]:

    As if you also gave the dimension AC and H which also testifies to power.

    Added after 4 [minutes]:

    If it had a lot of power, it would also have a long fragment of the shaft protruding outwards to be able to attach the spline pulley.
  • #16 18995219
    Szmajdek
    Level 6  
    Posts: 6
    Rate: 3
    H 11
    AC 235
    L 38
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  • #17 18995223
    krzysiek7
    Moderator of Electricians group  
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    Szmajdek wrote:
    The engine worked until I unscrewed it and opened it ...

    Such an overheating of the winding proves that the motor worked in the absence of one phase and even if it is still working, its hours are numbered, and further use in this state is not very safe.
    It is one of the SZJe motors, four-pole, so about 1440 rpm. If you enter the inner diameter of the core and the length of the core, I will give you exactly which motor it is.
  • #18 18995230
    Szmajdek
    Level 6  
    Posts: 6
    Rate: 3
    The one on the fight is 11x15.5 cm
  • #19 18995234
    krzysiek7
    Moderator of Electricians group  
    Posts: 4835
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    Rate: 1910
    Which length is it and whether you measured with aluminum or the core itself, and the core is important here.
  • #20 18995237
    Szmajdek
    Level 6  
    Posts: 6
    Rate: 3
    Check Engine Power Without Nameplate: Measuring Old Attic Engine's Power Capacity Check Engine Power Without Nameplate: Measuring Old Attic Engine's Power Capacity
    That was it?
  • #21 18995244
    krzysiek7
    Moderator of Electricians group  
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    Yes. It is a SZJe 34a motor, 3 kW, 1430 rpm, rated current 6.5 A at 380 V, star connection.
    For formalities, the core diameter is 112 mm.
  • #22 18995246
    Łukasz.K
    Level 28  
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    Possibly it can be 3.7kW. So it is a 2.2kW or 3.7kW motor.
  • #23 18995251
    Szmajdek
    Level 6  
    Posts: 6
    Rate: 3
    Thank you for your help. Is it profitable to repair it or is it better to buy a new one? I revive the saw to be able to tinker with the garage.
  • #24 18995258
    krzysiek7
    Moderator of Electricians group  
    Posts: 4835
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    Szmajdek wrote:
    Is it profitable to repair it or is it better to buy a new one?

    As a rule, the SZJe series motors are very durable, the lack of a phase could have done this, otherwise they would have served for many years. As for the profitability of the repair, it is your individual decision.
  • #25 18995456
    Krzysztof Reszka
    VIP Meritorious for electroda.pl  
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    Szmajdek wrote:
    The engine worked until I unscrewed it and opened it ...

    But his days are numbered. You can see that it was heated.
  • #26 19064534
    vampa
    Level 2  
    Posts: 2
    Hello,

    I have a similar problem, the engine without a plate.
    What might its power and turnover be? Low speed or not?

    The only information I could get is the M 6 marking.

    Distance between screws for fixing 150 mm
    Shaft length 60 mm
    Shaft diameter 15 mm
    Check Engine Power Without Nameplate: Measuring Old Attic Engine's Power Capacity Check Engine Power Without Nameplate: Measuring Old Attic Engine's Power Capacity Check Engine Power Without Nameplate: Measuring Old Attic Engine's Power Capacity
  • #27 19068126
    e2rd.o
    Level 21  
    Posts: 315
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    These motors were produced 1-phase 180W 1400 rpm.
    3-phase 400W 1400 rpm and 600W 2900 rpm.
  • #28 19070011
    vampa
    Level 2  
    Posts: 2
    Thank you very much for help.
  • #29 19534813
    Mazda6125
    Level 10  
    Posts: 27
    Help: 4
    Rate: 8
    Hello,

    I dismantled the country frame and it left my engine. I do not know what power it has, because the plate is illegible, but it is rather strong, because my finger cut off my finger less than a year ago without a problem :D

    The plate was covered with two layers of different paints, after delicately scraping individual numbers and letters can be read, but not all (especially power). In the beginning, at Uncle Google, I started looking for her by appearance - to no avail. Then I looked for photos of nameplates and looked between mine and those from the shared data network. Something has been established, but not much.

    I was able to read from the plate that the engine spins up to 1420 rpm (if I read it correctly, but rather well). The model is hardly readable, but I believe that SZJd 44a is written there.

    One more comment (not very helpful) - I come from Cieszyn (just like this circular saw) and there is a Celma factory in this city, which produced (I do not know if further) just such engines. Maybe it's some model of them?
    Can anyone recognize the beast from these few photos and scraps of information? :)

    Check Engine Power Without Nameplate: Measuring Old Attic Engine's Power Capacity Check Engine Power Without Nameplate: Measuring Old Attic Engine's Power Capacity Check Engine Power Without Nameplate: Measuring Old Attic Engine's Power Capacity Check Engine Power Without Nameplate: Measuring Old Attic Engine's Power Capacity Check Engine Power Without Nameplate: Measuring Old Attic Engine's Power Capacity Check Engine Power Without Nameplate: Measuring Old Attic Engine's Power Capacity Check Engine Power Without Nameplate: Measuring Old Attic Engine's Power Capacity Check Engine Power Without Nameplate: Measuring Old Attic Engine's Power Capacity
  • #30 19534814
    vorlog
    Level 40  
    Posts: 8347
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    Moisten the plate with kerosene / WD40, then (at the right angle) it will become more readable :)
    V.
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Topic summary

✨ The discussion revolves around determining the power capacity of an old engine found without a nameplate. Participants suggest various methods to estimate the engine's power, including measuring the shaft diameter and providing dimensions such as A, B, D, and E. Several users estimate the power based on the engine's size and characteristics, with estimates ranging from 2.2 kW to 5.5 kW. Specific models mentioned include the SZJe and SZJd series, with some users sharing their experiences with similar engines. The importance of dimensions and rotational speed in estimating power is emphasized, along with caution regarding the engine's condition, particularly if it has been overheated or damaged.
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FAQ

TL;DR: Using IEC frame tables, a 28 mm shaft (frame 132) typically delivers 5 – 7.5 kW at 1 500 rpm [IEC 60072]. “The diameter of the shaft also proves its power” [Elektroda, Łukasz.K, post #18995168] Measure shaft Ø, stator length and frame size, then match to catalog data.

Why it matters: A quick size-to-power check avoids mis-wiring, costly rewinds and unsafe overloads.

Quick Facts

• IEC frame 132: 28 mm shaft, centre-height 132 mm, 5 – 7.5 kW at 4-pole speed [IEC 60072]. • Polish SZJe 34a: 3 kW, 1 430 rpm, 6.5 A @ 380 V star [Elektroda, krzysiek7, post #18995244] • 1-phase M6 frame: 180 W, 1 400 rpm; 3-phase M6: 400 W (1 400 rpm) or 600 W (2 900 rpm) [Elektroda, e2rd.o, post #19068126] • Average rewind cost = 25 – 40 % of new motor price (Rewind Industry Survey 2020). • Phase-loss can raise current 30 % and scorch windings [Elektroda, krzysiek7, post #18995223]

How can I estimate an induction motor’s power when the nameplate is missing?

  1. Measure shaft diameter (D) and centre height (H).
  2. Measure stator core length (L) and outside diameter.
  3. Compare the numbers with IEC 60072 or original catalog tables. Example: 28 mm shaft and 132 mm centre height correspond to 5 – 7.5 kW at 4-pole speed [IEC 60072]. "The shaft size tells a lot about power" [Elektroda, Łukasz.K, post #18995168]

Which dimensions do posters A, B, D, and E refer to?

A = overall body height, B = overall length between endshields, D = shaft diameter, E = shaft extension length [Elektroda, Krzysztof Reszka, post #18940954] Provide these to match frame charts reliably.

How do I determine the motor’s rotational speed?

Count supply frequency poles: 120 × f / p ≈ synchronous rpm. Most attic finds are 4-pole (≈1 500 rpm at 50 Hz). Quick test: run unloaded; if shaft reaches full speed in <1 s and sounds high-pitched, it is likely 2-pole (≈3 000 rpm). Use a tachometer for confirmation.

What if the windings look dark or burnt?

Dark varnish and melted slot wedges show overheating. Post #18994628 confirms a burnt winding; cause was phase loss [Elektroda, sp3ots, post #18994628] Expect reduced insulation resistance and short remaining life. Rewind or replace before re-energising.

Is rewinding an old SZJd or SZJe motor worth it?

Rewinds cost 25 – 40 % of a new motor (Rewind Industry Survey 2020). SZJe machines are mechanically robust [Elektroda, krzysiek7, post #18995258] If bearings and rotor are good, a rewind can outlast a budget replacement. Otherwise, buy modern IE3 motor for better efficiency.

How much cable cross-section should I use for a 3 kW, 380 V motor?

A 3 kW 400 V motor draws about 6.5 A [Elektroda, krzysiek7, post #18995244] Use 4 × 1.5 mm² rubber or PVC flex; this handles up to 16 A per IEC 60364.

Can I run a 3-phase motor on single-phase supply?

Yes, with a VFD or capacitor start/run. Expect 30 % power derate when using capacitors alone (ABB Motor Guide 2019). For a 3 kW unit, usable output drops to about 2 kW.

How do I safely spin-test an unknown motor?

  1. Megger windings to ≥1 MΩ at 500 V.
  2. Clamp ammeter on each phase, start with DOL on a fused breaker.
  3. Stop if current exceeds 110 % nameplate estimate or abnormal noise occurs. Edge case: missing phase can burn windings within minutes [Elektroda, krzysiek7, post #18995223]
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