Functions and Application (dt/dv filters applied to cables over 100m in length)
The DV/DT filter protects your servo motor by minimizing the peak voltage that occurs at the motor terminals. It also offers maximum protection for cables and motor windings from premature aging or dielectric breakdown. All these result in extended motor life, improved reliability and uptime. The use of an electrical filter also minimizes electromagnetic interference to adjacent equipment, power or signal circuits, reduces current leakage that might occur in the ground wire, and attenuates the interference as the contactor between the filter and the motor is switched. This DV/DT filter design meets the output voltage requirements of IEC 60034-17, 60034-25.
Normal Cable Parameters (without Input Reactor)
Power rating (KW) | Max. current (A) | Main cable (UL AWG) | Rated Inductance | Rated capacitance (conductor to conductor) | Rated capacitance conductor to conductor & shield | Rated Conductor DC Resistance @20 °C | Max. Recommended Current @30 °C (Amps) | ||||||
| (Uh/ft) | (Uh/m) | (H/Km) | (pF/ft) | (pF/m) | F/KM | (pF/ft) | (pF/m) | (Ohm/1000ft) | (Ohm/1000m) | ||||
| 5.5 | 12.8 | AWG14 | 0.213 | 0.699 | 6.988189E--04 | 23 | 75.5 | 7.545932E--08 | 42 | 137.8 | 2.52 | 8.268 | 25 |
| 11 | 24.8 | AWG10 | 0.184 | 0.604 | 6.036745E--04 | 29 | 95.1 | 9.514436E--08 | 53 | 173.9 | 0.989 | 3.245 | 40 |
The output dt/dv of a VFD is 3000V/μS. According to the power distribution parameters of a shielded cable, the critical length of traveling wave reflection is about 15m. If the cable is less than 15m, the output reactor can be spared.
Due to the inconformity of the distribution parameters of cables in the engineering industry, the output dt/dv of a servo motor is much larger than 3000V/μS, so it is advised that reactors with 1% voltage drop should be used if the cable length is more than 10m.
Differential Mode Test Data
| Switch frequency | Test point | 50m unshielded cable | 150m unshielded cable | 500m unshielded cable | ||||||
| Ubus | Upeak | dv/dt | Ubus | Upeak | dv/dt | Ubus | Upeak | dv/dt | ||
| 4KHz | Drive output | 525 | 603 | 2275 | 525 | 588 | 2218 | 525 | 603 | 2394 |
| Fliter output | 537 | 594 | 63 | 528 | 609 | 98 | 528 | 744 | 69 | |
| Moter side | 501 | 564 | 70 | 501 | 570 | 109 | 438 | 696 | 79 | |
| 8KHz | Drive output | 528 | 603 | 2353 | 528 | 594 | 2215 | 525 | 603 | 2275 |
| Fliter output | 525 | 573 | 68 | 528 | 615 | 91 | 525 | 744 | 69 | |
| Moter side | 501 | 537 | 81 | 498 | 582 | 101 | 414 | 672 | 82 | |
| Without dt/dv filters, the peak voltage at motor terminals can reach over 1000V. (Cable length: 100m ) | ||||||||||
Common Mode Test Data
| Operating current(A) | Load | CM voltage(V) | CM current(A) |
| 538 | 13 | ||
| 76 | 80% | 275.5 | 1.9 |
| CM Test Date of 95A dv/dt filter (Cable length: 100m ) | |||
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