Elmo HARmonica, HARSFEN0602 software manual 118, Torque command filter

HARSFEN0602ElmoHARmonicaSoftwareManual					PRELIMINARYDRAFT
τ =	− PL[2]
		−	CL[1]	
	log1			
			MC
				

With this selection, when PL[2] is set to MC, and after the current demand has been zero for a long time, the amplifier will permit a maximum of PL[2] seconds of peak current, and then switch to continuous current limiting.

For other settings PL[1], the maximum time, for which the peak current can be maintained,

	−	CL[1]		⋅τ seconds.
after the current demand has been zero for a long time, is - log1			
		PL[1]
			

The programming range for PL[2] is very limited. In most applications we recommend to leave PL[2] in its 3 seconds factory default.

Example:

The graph below shows the signals concerned with the current command limiting process for MC=6, PL[1]=6, PL[2]=3, and CL[1]=3.

The motor current demand is increases from zero to 6Amp at the time of 0, and is then decreased to 0 at the time of 5sec.

The state of the low-pass filter increases until it reaches the continuous current limit of 3 at the time of 3 sec. At that time, the LC flag is raised, and the motor current command is decreased to CL[1]=3Amp.

After the motor current command is set to zero, the state of the filter begins to drop. When the state of the filter drops to 2.7Amp = 90% of 3Amp, the LC flag is reset and the torque command limiting is again to 6Amp.

6
5						Application current demand
				motor current
				command
4
3
						Filter state
2
1						LC current limit
						Indication
0
0	1	2	3	4	5	6	7	8	9

118

10.2.1The torque command filter

The torque command filter prevents that abrupt torque commands shall generate large current overshoots.

The filter is very simple, having a single time constant and a rate limiter. The parameter XP[6] defines the time constant: