OEM ENGINEERING GUIDE
How to Read a Universal Motor Performance Table
A performance table is a set of operating points, not a list of maximum values that can all be achieved at once. Here is how to read the columns, check the units and ask better questions before choosing a motor.
1. Read the test context first
Identify the model, supply, frequency and configuration before comparing numbers. A table from another voltage, controller, cooling arrangement or test procedure may not be directly comparable. Measurement boundaries also matter: motor-only efficiency and motor-plus-drive efficiency are not the same.
The example below uses the representative catalog data currently shown on the Zhanye ZYU7635 page, for a nominal 230 V / 50 Hz configuration. It is a reading example, not a newly performed test or a continuous-duty rating.
2. Keep each operating point together
| Parameter | No Load | Max Efficiency | Max Output | Max Torque |
|---|---|---|---|---|
| Speed (RPM) | 15,996 | 9,089 | 8,423 | 7,075 |
| Torque (mN·m) | 4.63 | 375.24 | 414.39 | 470.04 |
| Output power (W) | 7.76 | 357.11 | 365.49 | 348.20 |
| Input power (W) | 266.25 | 633.98 | 671.03 | 702.60 |
| Efficiency (%) | 2.91 | 56.33 | 54.47 | 49.56 |
Read down one column. For example, the Max Output column pairs 365.49 W with 8,423 RPM and 414.39 mN·m. Do not combine its power with the 15,996 RPM from the No Load column.
- No Load: the catalog’s low-load reference point. This table reports small nonzero torque and output values; the test setup needs clarification before interpreting them as useful external shaft output.
- Max Efficiency: the point labeled as the best efficiency in the reported test.
- Max Output: the greatest output reported by this table, not an automatic continuous rating.
- Max Torque: the highest torque listed in this test. Its speed is 7,075 RPM, so it is not a stall-torque measurement.
3. Separate input power from shaft output
Electrical input powers the motor; mechanical output is delivered at the shaft. Shaft power is calculated from torque and angular speed. Efficiency compares mechanical output with electrical input.
Efficiency (%) = output power ÷ input power × 100
Convert mN·m to N·m by dividing by 1,000. At the listed Max Output point, 414.39 mN·m becomes 0.41439 N·m. Using 8,423 RPM gives approximately 365.51 W, close to the listed 365.49 W; rounded table entries can produce small differences.
Using the published power values gives 365.49 ÷ 671.03 × 100 ≈ 54.47%. The 671.03 W electrical input must not be advertised as 671.03 W of shaft output.
4. Do not confuse power factor with efficiency
Power factor describes the relationship between real electrical power and apparent power. For a single-phase measurement, apparent power is RMS voltage multiplied by RMS current. Efficiency instead compares useful mechanical output with electrical input.
With distorted waveforms, total power factor is not simply the cosine of the fundamental voltage/current phase angle. Use the measured input power and the measurement method provided with the test, rather than assuming voltage × current equals watts.
5. Identify what the table cannot prove
A few operating points do not define the full permissible operating envelope. They do not, by themselves, establish a continuous rating, a safe overload duration, noise performance or a guaranteed service life. Time ratings must be considered separately from a power figure.
Do not reconstruct an unverified curve. Do not assume a straight speed–torque line or extrapolate stall torque from these four points. Request the relevant measured curve and approved limits for the selected configuration.
6. Ask for the data that matches your load
Send the supplier your required speed and torque, operating cycle and supply conditions. Ask which measured point is closest, what the continuous or intermittent limits are, and which cooling and temperature conditions apply. Request the viewing direction for CW/CCW and the test basis for any quoted life figure.
The purpose is not to find the largest number. It is to establish whether a specific configuration can meet your application’s requirements under agreed conditions.