# Thu 7 aug 2009 # original lab notes # k headley # [kecy, mellinger] Current and voltage probes were place on the DC power supply (dcps) inputs to observe the startup behavior of the system when it stalls under cold conditions. MC is an Elmo (read-only) parameter defining the maximum allowable current for the Elmo drive. For our Elmo, MC=20. PL[1] defines the peak current limit; its maximum allowed value is MC. CL[1] defines the continuous current limit; its maximum value is MC/2. The motor current (torque) command is normally limited to its peak limit, as defined by PL[1]. After a short period of torque demand higher than CL[1], the torque command limit is decreased to CL[1]. If the current command has been raised to PL[1] from zero, after the time specified for peak duration (PL[2], in seconds), the motor current command will be limited to CL[1]. The motor current command remains limited to CL[1] until enough time has passed for the average requested torque command to fall below 90% of CL[1]. We set PL[1] and CL[1] to their maximum values: set PL[1]=MC=20 set CL[1]=MC/2=10 set DCPS=36V 5A set jv=150 started motor (BG) DCPS indicated current limit current probe output (PWM waveform) hits CL limit and draws DCPS down to 0, DCPS current limit resets elmo Does increasing DCPS current limit help? set PL[2]=3 (max allowed) set DCPS 36V 10 A [double previous] DCPS indicates current limit, elmo reset What is measured current when over-current trip occurs using our deployment defaults with high current? set DCPS 36V 10 A, PL[1]=10, CL[1]=5 DCPS current limits, probe output reads 11.3A pp Can it start (and what is measured current) using max PL and CL, and maximum DCPS current limit? set DCPS 36V 18 A set PL[1]=20 CL[1]=10 DCPS current limits at 11.3A pp Not sure if problem is with Elmo, power supply, or probe. CK used known resistor values to verify that - DCPS will supply 18A at 36V - Current probe is correctly calibrated [ck]: Scope probe read 1.3x actual value (e.g. 13A read = 10A actual) [kh]: Meanwhile, talked to Ed Mellinger about the results so far, described waveforms we were seeing... [em]: Should not see PWM waveform at supply - would expect to see a smoother DC with some ripple, but not square wave PWM. Is there capacitance at the Elmo terminals? (No) DC supplies (Xantrex we are using) get confused by fast AC/PWM draws and can trip current limit. Caps at the drive terminals can filter so DC is supply DC and Cap is supplying AC/PWM to the load. Also, cap ESR (equivalent series resistance) increases at low temp, making it more difficult to keep bus voltage up. Test again to verify probe calibration (CL, PL should make sense) set DCPS 36V 10 A set PL[1]=8 CL[1]=5 DCPS current limits at 10.6A (probe) 10.4/1.3=8=PL[1]: OK Test again with different PL and CL set DCPS 36V 10 A set PL[1]=6 CL[1]=5 current limit at ?A (higher than expected) Now try with added capacitance at DCPS terminals (not ideal) set DCPS 36V 10 A set PL[1]=8 CL[1]=5 w/ 220 uF at DC supply terminal: can start and run at 150 c/s, but not 340 c/s w/ 320 UF at DC supply terminal: can start and run at 340 c/s What steady state current is required to operate at our top speed (340 counts/sec) set DCPS 36V 10 A, set PL[1]=10 CL[1]=8 Duty cycle (from scope) is 0.39 Equivalent DC current = [Active Current * PWM Duty Cycle] Active Current (Elmo composer) is 6.8A (2.7 A DC at supply) to start cold and run at 340 c/s steady state 6.8 A*0.39 PWM duty cycle=2.7 A Next steps: we need to try this using the FOCE hardware; CK will determine appropriate capacitance values. KH will ask RB from Elmo about appropriate capacitance values. We will run tests next week (Tuesday) to capture wave forms to document the problem, test on FOCE hardware, and produce quantitative data about the power consumption associated with the water, drive train and oil. Also found this (though our Elmo reports 0 for AN[7]): ------------------------------------------------------------------------ AN[1] reports the analog input #1 value after offset correction (AS[1]), in volts. AN[2] reports the analog input #2 value after offset correction (AS[2]) in volts. AN[3] reports the measured current in the motor A phase, in amperes. AN[4] reports the measured current in the motor B phase, in amperes. AN[5] reports the measured current in the motor C phase, in amperes. AN[6] reports the line voltage value, in volts. AN[7] reports the duty cycle value of the PWM signal after offset correction in fractional units Analog input #1 serves as reference input for analog torque or analog velocity command while in auxiliary reference mode (RM=1). AN[7] is available after the first MO=1. Each of ElmoÕs SimplIQ drives support a different number of analog inputs. For specific details consult the driveÕs Installation Guide. ------------------------------------------------------------------------ Wrote RB at Elmo about flash problem, resolved as follows: ------------------------------------------------------------------------ Tried to write parameters to flash using SV command sv Error [54]: 'sv': Bad Data Base!; cd NullAddres=0x0 FailureAddress=0x0 Called Handler= Database Stats:SP Err=21 ec 54 The error indicates that parameter SP is out of range; it is a parameter that isn't needed in UM=2, but still must be set < VH,VL. After setting SP