Hitachi X200 Series instruction manual Emi

A−3

DC Braking	The inverter DC braking feature stops the AC commutation to the
	motor, and sends a DC current through the motor windings in order
	to stop the motor. Also called “DC injection braking,” it has little	Appendix
	effect at high speed, and is used as the motor is nearing a stop.
Deadband	In a control system, the range of input change for which there is no	A
	perceptible change in the output. In PID loops, the error term may
	have a dead band associated with it. Deadband may or may not be
	desirable; it depends on the needs of the application.
Digital Operator	For Hitachi inverters, “digital operator panel” (DOP) refers first to
Panel	the operator keypad on the front panel of the inverter. It also includes
	hand-held remote keypads, which connect to the inverter via a cable.
	Finally, the DOP Professional is a PC-based software simulation of
	the keypad devices.
Diode	A semiconductor device that has a voltage-current characteristic that
	allows current to flow only in one direction, with negligible leakage
	current in the reverse direction. See also Rectifier.
Duty Cycle	1. The percent of time a square wave of fixed frequency is ON (high)
	versus OFF (low).
	2. The ratio of operating time of a device such as a motor to its
	resting time. This parameter usually is specified in association
	with the allowable thermal rise for the device.
Dynamic Braking	For the L200 inverter models, the braking unit and braking resistor
	are optional (external) components. The dynamic braking feature
	shunts the motor-generated EMF energy into a special braking
	resistor. The added dissipation (braking torque) is effective at higher
	speeds, having a reduced effect as the motor nears a stop.
Error	In process control, the error is the difference between the desired
	value or setpoint (SP) and the actual value of a the process variable
	(PV). See also Process Variable and PID Loop.
EMI	Electromagnetic Interference - In motor/drive systems, the switching
	of high currents and voltages creates the possibility of generating
	radiated electrical noise that may interfere with the operation of
	nearby sensitive electrical instruments or devices. Certain aspects of
	an installation, such as long motor lead wire lengths, tend to increase
	the chance of EMI. Hitachi provides accessory filter components you
	can install to decrease the level of EMI.
Four-quadrant	Referring to a graph of torque versus direction, a four-quadrant drive
operation	can turn the motor either forward or reverse, as well as decelerate in
	either direction (see also reverse torque). A load that has a relatively
	high inertia and must move in both directions and change directions
	rapidly requires four-quadrant capability from its drive.