Hoisting application & General: Slipping at slow speed & Holding Brake issues

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Following post is providing some advices and guidance in realizing a hoisting application

There are also some possible solutions for Holding brake issues - like when the holding brake does not engage at the right time or the load slips a bit before the holding brake engages.

For detailed information please also refer to the B&R support channels.

Mandatory and obvious first checks in hoist applications:

  • Motor nameplate
    • Has the correct motor nameplate been entered in the configuration of the P66? (Nominal current, nominal power etc…)
  • Tuning:
    • Has tuning been performed?
    • What efficiency class does the motor have?
      • If IE1 or IE2 (efficiency class 1 or 2), NPR tuning should be used.
        • To switch to NPR, enter “100” in the parameter “power factor”
  • Parameter: “BRA”:
    • What is the setting of BRA? Is a braking resistor used?
      • IF braking resistor is used: Have you tried settings DYNA or “NO” with the braking resistor?
      • ELSE leave BRA on YES

Further parameter adaptions, next steps:

For the next changes, make sure to test and document behaviour one by one, as the combination of these parameters all take part in either
improving or making the behaviour worse. In the end, the changes should fit for most cases, in the same order as it is written down.
Nevertheless feel free do adapt and combine for whats best, after testing:

  • Hardware Update:
    In most cases P66 dropping the load when engaging holding Brake occured in older Versions (lower than V2.3.2.0)
    • The Version 2.3.2.0 changed the behaviour and configuration of BLC management, please use / test this or later versions.
    • Adapt the BLC parameter to what is currently used (see User’s Manual).
    • Make sure you are really braking correctly so that BLC is beeing used.

Changes for slipping / dropping at low speed:

  • Parameter: “LSP”:
    • What is it set to? (If you cant find it, set “axis management” → “Reference model” to “Hz”)
    • Change the LSP parameter to the motor slip frequency.
      • You can calculate the slip frequency of your motor with the following formula:
        NSP = Nominal speed
        Nsync = Nominal speed for synchronous motor with same polepairs
        FRS = Rated frequency

Slip = ((Nsync - NSP)/Nsync)*FRS

Here an example:

NSP= 1380rpm
Nsync = 1500rpm
FRS = 50Hz
(1500-1380)/1500)*50 = 4Hz

This example-asynchronous motor, has a slip frequency of 4Hz .
Therefore LSP = 4Hz.

If motor behaves shaky or bad with the calculated LSP value:

  • Adapt the LSP value and set it higher or lower, depending on whether the motor behaviour improves or not.
  • Also adapt parameter BEN (additional if LSP does not help. Check what BEN does in the User’s Manual so that you can adapt it correctly)

Rise Parameter “SLP”:

  • SLP = Slip compensation.
    • Default set to 100%.
    • Rise it in small steps ~“10” and see if it helps.

Parameter “BRR”:
Test setting the BRR Parameter to eg. 0,2s and check results.

  • Rise or lower the time if nothing changes
  • If it makes it worse or does not help at all - leave it to default.

Adapt SPG and SIT:

The smaller SIT is set:

  • the faster the steady state is reached,
  • the greater the risk of overshootThe larger SPG is set:

The larger SPG is set:

    • the faster the steady state is reached,
    • the greater the danger of overshoot

It is a PI control
SPG influences the P-part of the controller
SIT influences the I-part of the controller

Magnetic force is too low and still slipping:

  • Parameter “IBR”:
    • Increase IBR in 0.5A steps (Holding brake parameter).
      • IBR should stay lower than nominal current)
    • IF no improvement: Increase “IDA” (tuning result parameter).
      • ELSE limit the lowest speed. (Do not drive that slow as this is causing the slipping)
        • IF customer does not like this (to limit lowest speed) and nothing above helps, we need:

Requested Data:

  • The Project with the most recent configurations
  • A picture of the motor nameplate (on the motor itself)
  • Trace: LFRD, RFR, CMDD, ETAD, OTR, LCR. - In the error case.
  • Optional: Braking resistor informations (calculation on dimension of braking resistor)
  • Optional: Video of the Inverter display when error occures (is it blinking?)

If nothing helps: Handle the case with the B&R support channel and adapt this page if new findings occur.

Finally, I would like to say a big thank you to @Radivoj.Grujicic who was the original creator of this well prepared guide!

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great one @josef.stoellinger. thanks for that.