Baldor ID15J1F50-ER Installation And Operating Manual

Contents

Baldor ID15J1F50-ER Installation And Operating Manual Manual pdf 68 page image

MN715J Troubleshooting 5-9Electrical Noise ConsiderationsAll electronic devices are vulnerable to significant electronic interferencesignals (commonly called ìElectrical Noiseî). At the lowest level, noise cancause intermittent operating errors or faults. From a circuit standpoint, 5 or 10millivolts of noise may cause detrimental operation. For example, analogspeed inputs are often scaled at 5 to 10VDC maximum with a typicalresolution of one part in 1,000. Thus, noise of only 5 mV represents asubstantial error.At the extreme level, significant noise can cause damage to the drive.Therefore, it is advisable to prevent noise generation and to follow wiringpractices that prevent noise generated by other devices from reachingsensitive circuits. In a control, such circuits include inputs for speed, controllogic, and speed and position feedback, plus outputs to some indicators andcomputers.Relay and Contactor CoilsAmong the most common sources of noise are the ever-present coils ofcontactors and relays. When these highly inductive coil circuits are opened,transient conditions often generate spikes of several hundred volts in thecontrol circuit. These spikes can induce several volts of noise in an adjacentwire that runs parallel to a control-circuit wire.Figure 5-4 illustrates noise suppression for AC and DC operated coils.Figure 5-4 Diode with DC CoilAC Coil DC CoilRC snubber0.47 f Diode-+33 Wires between Controls and MotorsOutput leads from a typical 460 VAC drive controller contain rapid voltagerises created by power semiconductors switching 650V in less than amicrosecond, 1,000 to 10,000 times a second. These noise signals cancouple into sensitive drive circuits. If shielded pair cable is used, the couplingis reduced by nearly 90% compared to unshielded cable.Even input AC power lines contain noise and can induce noise in adjacentwires. In some cases, line reactors may be required.To prevent induced transient noise in signal wires, all motor leads and ACpower lines should be contained in rigid metal conduit, or flexible conduit. Donot place line conductors and load conductors in same conduit. Use oneconduit for 3 phase input wires and another conduit for the motor leads. Theconduits should be grounded to form a shield to contain the electrical noisewithin the conduit path. Signal wires - even ones in shielded cable shouldnever be placed in the conduit with motor power wires.