Predictika · Frequency inverter DC bus designs

An AI sales agent's inverter DC bus design, checked before it goes out

An AI sales agent prepares a common DC bus for several frequency inverters, with the F1 semiconductor fuse, the supply and the wiring. Before it goes out, the agent sends it to Predictika, which checks it against a declarative model of the manufacturer's published rules for interconnected operation and returns a verdict, every reason and the figures it computed.

Scope: Lenze i550 cabinet frequency inverters, I55AE and I55BE, 0.37 to 110 kW, on a common DC bus with one infeed unit and an F1 semiconductor fuse. See everything this validator covers

This validator models a common DC bus of Lenze i550 cabinet frequency inverters (up to three drives per bus in this version), not just the scenarios shown below.

  • Drives — the 29 inverter designations in the published fuse table, from I55AE137F (0.37 kW) to I55AE411F (110 kW), including the B variants I55BE230F, I55BE240F and the I55xE275F to I55xE322F and I55BE330F sizes. The drive with the smallest permitted fuse sets the limit for the shared F1 fuse.
  • F1 fuse — rated current not above that limit, a 2-pole semiconductor fuse from the table of listed types (Eaton/Bussmann, Littelfuse, Mersen, SIBA, Siemens, with the ratings each lists), and a short circuit rating of 50 kA at most.
  • Supply and wiring — a single infeed unit, DC supply from a rectified mains of 480Y/277 V at most, a DC grid voltage of 450 V to 750 V (rated DC input currents are tabulated at 565 V and 675 V; other voltages need approval), an external DC distribution point for several drives, and conductors rated for at least 122 percent of the AC-side fuse when that fuse provides overload protection. Overload protection by other means needs approval.
  • Figures — the maximum F1 rating the quote states is compared with the table, and the combined rated DC input current of the drives is computed from the published ratings.

Any DC bus of these drives that touches these rules is in scope — not only the scenarios pictured here. Not covered: prices (the document has none, so there is no price build-up or line-item quote), individual fuse protection of every unit (a different arrangement), DC buses with more than one infeed, UL motor-group fusing, other Lenze drive series and the cable cross-section tables, which the manufacturer leaves to the system designer.

The AI sales agentBuilds the DC bus design from the conversation and says it is ready.
Predictika validatorChecks every rule at once and returns the verdict, each finding, and the computed figures.

7 scenarios in 3 groups · each group runs from the agent’s first attempt to the outcome · click one to switch

What the agent proposes

The AI sales agent says

Illustrative agent statement. The validator receives the structured request below.

Proposing agent: AI sales agent (scripted)

Before sending, the agent must call Recorded run

Predictika validator


      

        
        
        
      

      
Waiting for the call.

      
    

  

  
  

    
Where rules-based CPQ gets it wrong
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Our assessment of what a typical rules-based CPQ (product rules, price rules and validation rules, as in Salesforce CPQ) does with the same cases. It is a judgment about effort and reliability, not a claim that nothing can be built.

    
What the validator caughtTypical rules-based CPQPredictika
The smallest fuse limit among all drives on the bus sets the limit for the shared fuseOnly with care
A roll-up of the minimum over a variable set of drives, held in a formula; every new drive size is another row to maintain.		Each drive's limit is looked up and the smallest is compared with the F1 rating on every call.
The B variants of the same size have a lower limit than the A variantsOnly with care
The limit depends on the full designation, not just the size, so it needs a lookup per designation, 29 of them here.		The limit is part of the model for each designation.
Fuse makers that list some ratings and not othersOnly with care
A table of five makers by eight ratings checked against the chosen fuse; easy to get wrong when a maker drops or adds a rating.		Maker and rating are checked against the listed types together.
Wiring rated for 122 percent of the AC-side fuseOnly with workarounds
Two free-entry numbers compared by a formula that holds only when the AC fuse provides the overload protection; a product-rule engine has no natural place for it.		The comparison runs on every call, only when the AC fuse is the overload protection.
Short circuit rating, mains voltage and number of infeedsOnly with workarounds
These are properties of the cabinet and the plant, not of the catalog, so a catalog-driven rule set has nowhere to hold them.		Plant figures travel with the design and are checked with the product choices.
Every problem returned in one answerOnly with workarounds
Rules tend to fire as a step is completed, so an engineer often fixes one error and meets the next.		All findings come back together, whatever order the choices arrived in.

  

  

    
What this validator catches: findings from its test cases
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Every rule is checked on every call, in any order the choices arrive; one problem never hides another. Blocking findings stop the quote; approval findings need a person to sign off; everything else is computed.

    
1The F1 fuse is rated 80 A, but the drive with the smallest permitted fuse on this bus limits F1 to 50 A.
2The quote states a maximum F1 fuse of 80 A; the fuse table gives 50 A for the drives on this bus.
3The F1 fuse is rated 50 A, but the drive with the smallest permitted fuse on this bus limits F1 to 16 A.
4The fuse table lists no SIBA semiconductor fuse of 350 A.
5The fuse table lists no Littelfuse semiconductor fuse of 16 A.
6The fuse table lists no Siemens semiconductor fuse of 40 A.
7The F1 fuses in the DC feed must be 2-pole (+UG and -UG); this quote has 1 pole.
8The short circuit current rating of the circuit may be 50 kA at most; this circuit is rated 65 kA.
9The DC supply voltage must be generated from a rectified AC voltage of 480Y/277 V at most; the mains voltage is 500 V.
10The permissible DC grid voltage range is 450 V to 750 V; this bus runs at 440 V.
11The rated DC input currents are tabulated only at 565 V and 675 V; this bus runs at 440 V, so the currents must be confirmed with Lenze.
12The permissible DC grid voltage range is 450 V to 750 V; this bus runs at 760 V.
13The rated DC input currents are tabulated only at 565 V and 675 V; this bus runs at 760 V, so the currents must be confirmed with Lenze.
14The rated DC input currents are tabulated only at 565 V and 675 V; this bus runs at 450 V, so the currents must be confirmed with Lenze.
15The rated DC input currents are tabulated only at 565 V and 675 V; this bus runs at 600 V, so the currents must be confirmed with Lenze.
16Overload protection by the AC-side fuse needs conductors rated for at least 122 percent of its rated current; the wiring is rated 60 A against a 50 A AC fuse.
17Overload protection of the DC bus wiring by means other than the AC-side fuse is left to the system designer; the design must be reviewed.
18The Lenze document covers a DC bus supplied by exactly one unit; this bus has 2 infeed units. Other topologies must be taken up with a Lenze representative.
19The Lenze document covers a DC bus supplied by exactly one unit; this bus has 0 infeed units. Other topologies must be taken up with a Lenze representative.
20The i550 terminals do not allow looping the DC potentials through, so several drives on one DC bus need an external DC distribution point in the control cabinet.
21The quote states a maximum F1 fuse of 40 A; the fuse table gives 50 A for the drives on this bus.
22The F1 fuse is rated 350 A, but the drive with the smallest permitted fuse on this bus limits F1 to 16 A.
23The permissible DC grid voltage range is 450 V to 750 V; this bus runs at 800 V.
24Overload protection by the AC-side fuse needs conductors rated for at least 122 percent of its rated current; the wiring is rated 40 A against a 40 A AC fuse.
25The quote states a maximum F1 fuse of 350 A; the fuse table gives 16 A for the drives on this bus.
26The rated DC input currents are tabulated only at 565 V and 675 V; this bus runs at 800 V, so the currents must be confirmed with Lenze.

  

  

    
Scenarios and results
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The recorded result of the validator for each scenario on this page: the request the AI agent sent, the verdict, and every finding, in the order they appear above.

    
1. Packaging line, F1 sized for the biggest drive: Three drives on a packaging line with an 80 A F1 fuse

    
The agent's request. Please quote a common DC bus for 3 Lenze i550 inverters (I55AE240F, I55AE230F and I55AE222F), with a 2-pole Siemens semiconductor fuse of 80 A at F1, overload protection by a 40 A AC-side fuse with DC bus wiring rated 60 A, fed by 1 infeed unit on a 400 V mains with a 565 V DC bus and a 50 kA short circuit rating, with an external DC distribution point. The quote states a maximum F1 fuse of 80 A. It is ready to send.

    
Verdict: Blocked.

    
    
      
  • F1 fuse above the drive limit. The F1 fuse is rated 80 A, but the drive with the smallest permitted fuse on this bus limits F1 to 50 A.
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  • Stated F1 limit differs from the table. The quote states a maximum F1 fuse of 80 A; the fuse table gives 50 A for the drives on this bus.
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2. Packaging line, F1 sized for the biggest drive: The agent resubmits after fixing the errors

    
The agent's request. Please quote a common DC bus for 3 Lenze i550 inverters (I55AE240F, I55AE230F and I55AE222F), with a 2-pole Siemens semiconductor fuse of 50 A at F1, overload protection by a 40 A AC-side fuse with DC bus wiring rated 60 A, fed by 1 infeed unit on a 400 V mains with a 565 V DC bus and a 50 kA short circuit rating, with an external DC distribution point. The quote states a maximum F1 fuse of 50 A. It is ready to send.

    
Verdict: Allowed.

    
    
      
  • Bus summary. The drive with the smallest permitted fuse limits F1 to 50 A; the drives need 26.9 A of rated DC input current together at the chosen bus voltage.
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3. Large drives on a 480 V mains: Three large drives with a 350 A fuse

    
The agent's request. Please quote a common DC bus for 3 Lenze i550 inverters (I55AE411F, I55AE390F and I55AE375F), with a 2-pole SIBA semiconductor fuse of 350 A at F1, overload protection by a 300 A AC-side fuse with DC bus wiring rated 400 A, fed by 1 infeed unit on a 480 V mains with a 700 V DC bus and a 65 kA short circuit rating, with an external DC distribution point. The quote states a maximum F1 fuse of 350 A. It is ready to send.

    
Verdict: Blocked.

    
    
      
  • F1 fuse above the drive limit. The F1 fuse is rated 350 A, but the drive with the smallest permitted fuse on this bus limits F1 to 315 A.
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  • Fuse type not in the fuse table. The fuse table lists no SIBA semiconductor fuse of 350 A.
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  • Short-circuit rating above 50 kA. The short circuit current rating of the circuit may be 50 kA at most; this circuit is rated 65 kA.
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  • Stated F1 limit differs from the table. The quote states a maximum F1 fuse of 350 A; the fuse table gives 315 A for the drives on this bus.
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  • DC input rating not tabulated at this voltage. The rated DC input currents are tabulated only at 565 V and 675 V; this bus runs at 700 V, so the currents must be confirmed with Lenze.
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4. Large drives on a 480 V mains: The agent resubmits after fixing the errors

    
The agent's request. Please quote a common DC bus for 3 Lenze i550 inverters (I55AE411F, I55AE390F and I55AE375F), with a 2-pole SIBA semiconductor fuse of 315 A at F1, overload protection by a 300 A AC-side fuse with DC bus wiring rated 400 A, fed by 1 infeed unit on a 480 V mains with a 700 V DC bus and a 50 kA short circuit rating, with an external DC distribution point. The quote states a maximum F1 fuse of 315 A. It is ready to send.

    
Verdict: Needs approval.

    
    
      
  • DC input rating not tabulated at this voltage. The rated DC input currents are tabulated only at 565 V and 675 V; this bus runs at 700 V, so the currents must be confirmed with Lenze.
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  • Bus summary. The drive with the smallest permitted fuse limits F1 to 315 A; the drives need 554.0 A of rated DC input current together at the chosen bus voltage.
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5. Large drives on a 480 V mains: The agent resubmits after fixing the errors

    
The agent's request. Please quote a common DC bus for 3 Lenze i550 inverters (I55AE411F, I55AE390F and I55AE375F), with a 2-pole SIBA semiconductor fuse of 315 A at F1, overload protection by a 300 A AC-side fuse with DC bus wiring rated 400 A, fed by 1 infeed unit on a 480 V mains with a 675 V DC bus and a 50 kA short circuit rating, with an external DC distribution point. The quote states a maximum F1 fuse of 315 A. It is ready to send.

    
Verdict: Allowed.

    
    
      
  • Bus summary. The drive with the smallest permitted fuse limits F1 to 315 A; the drives need 554.0 A of rated DC input current together at the chosen bus voltage.
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6. Three drives fed by two units: Three drives fed by two infeed units

    
The agent's request. Please quote a common DC bus for 3 Lenze i550 inverters (I55AE315F, I55AE318F and I55AE322F), with a 2-pole Mersen semiconductor fuse of 200 A at F1, overload protection by a 150 A AC-side fuse with DC bus wiring rated 200 A, fed by 2 infeed units on a 500 V mains with a 675 V DC bus and a 50 kA short circuit rating. The quote states a maximum F1 fuse of 200 A. It is ready to send.

    
Verdict: Blocked.

    
    
      
  • More than one infeed unit. The Lenze document covers a DC bus supplied by exactly one unit; this bus has 2 infeed units. Other topologies must be taken up with a Lenze representative.
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  • No external DC distribution point. The i550 terminals do not allow looping the DC potentials through, so several drives on one DC bus need an external DC distribution point in the control cabinet.
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  • Mains voltage above 480Y/277 V. The DC supply voltage must be generated from a rectified AC voltage of 480Y/277 V at most; the mains voltage is 500 V.
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7. Three drives fed by two units: The agent resubmits after fixing the errors

    
The agent's request. Please quote a common DC bus for 3 Lenze i550 inverters (I55AE315F, I55AE318F and I55AE322F), with a 2-pole Mersen semiconductor fuse of 200 A at F1, overload protection by a 150 A AC-side fuse with DC bus wiring rated 200 A, fed by 1 infeed unit on a 480 V mains with a 675 V DC bus and a 50 kA short circuit rating, with an external DC distribution point. The quote states a maximum F1 fuse of 200 A. It is ready to send.

    
Verdict: Allowed.

    
    
      
  • Bus summary. The drive with the smallest permitted fuse limits F1 to 200 A; the drives need 122.2 A of rated DC input current together at the chosen bus voltage.
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Narration transcript
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The text of the narrated walkthrough, step by step.

    
    
      
  1. Welcome to a demo of Predictika's Validator. An AI sales agent prepares a common DC bus for several frequency inverters, with the F1 semiconductor fuse, the supply and the wiring. Before it goes out, the agent sends it to Predictika, which checks it against a declarative model of the manufacturer's published rules for interconnected operation and returns a verdict, every reason and the figures it computed.
    2. 
      
  2. I will start with the first request by the agent.
    3. 
      
  3. The agent says. Please quote a common DC bus for 3 Lenze i550 inverters (I55AE411F, I55AE390F and I55AE375F), with a 2-pole SIBA semiconductor fuse of 350 A at F1. The quote states a maximum F1 fuse of 350 A. The rest of the request is on screen.
    4. 
      
  4. Before it goes out, the agent calls the validator.
    5. 
      
  5. Blocked, with four findings and one approval, all in one answer. The F1 fuse is rated 350 A, but the drive with the smallest permitted fuse on this bus limits F1 to 315 A. The fuse table lists no SIBA semiconductor fuse of 350 A. The short circuit current rating of the circuit may be 50 kA at most; this circuit is rated 65 kA. The other one is on screen.
    6. 
      
  6. The validator returned four blocking findings and one approval in one answer. A check that reads one field at a time would pass most of this; it shows only when the choices in the quote are checked against each other.
    7. 
      
  7. What this shows: for short circuit rating, mains voltage and number of infeeds, a rules-based CPQ can do this only with workarounds.
    8. 
      
  8. Now the agent resubmits.
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  9. The corrected request. It changes the f1 fuse rating to 315 A, the short circuit rating to 50 kA and the stated maximum F1 fuse to 315 A.
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  10. It calls the validator again.
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  11. Not blocked, but held for a person.
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  12. The four blocking findings are cleared; one approval remains for a person: DC input rating not tabulated at this voltage.
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  13. The agent resubmits once more.
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  14. The revised request. It changes the DC bus voltage to 675 V.
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  15. It calls the validator once more.
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  16. This time the validator clears it.
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  17. The earlier finding is cleared, and the validator's figure matches the quote.
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  18. Five problems caught in one call, fixed in two passes, and a clean quote. That is the value of Predictika's validator: catching mistakes before they reach the customer. Now you can try the other scenarios yourself.
    19.