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)

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 )