Transwave converter – plugged in motor, tripped RCD

[ell81Participant @ell81]

So I plugged the transwave into the 240v power supply and it lit up it’s light when turned on as usual. I turned it off, plugged an old 3 phase motor into the transwave socket, and turned on the transwave. This immediately tripped my house RCD and now the transwave won’t turn on when plugged in and switched on.

I opened the plug for the old 3 phase motor I tried to use with the transwave, and it only has 4 wires – 3 phase ones and the earth, even though the plug was for 5 core cable.

Does anyone know what the fault could be with my transwave now? Trying to run that motor off it must have damaged it somehow. Thanks.

[noel shelleyParticipant @noelshelley55608]

The reason for a 5 pin plug is to give 3phases, neutral and earth. For most uses the neutral is not used and normally not even available. A quick call to Transwave would be a good move. One thought is was the motor connected for 415V STAR or was it 220VDelta ? This option is common on modern motors but not always an option on old ones. It may be that the voltage sensitive (boost ) relay has failed ? Has the fuse for the socket or supply failed ? Good luck. Noel

[Les Jones 1Participant @lesjones1]

Check for leakage between the windings and the motor case using an insulation tester. (Megger.)
Les.

[gerry maddenParticipant @gerrymadden53711]

Is this a rotary converter ?

If so, my instructions say to get the converter running before connecting the load. If you just switch on the converter with the load already connected, you are asking your domestic supply to start two (or more) motors at the same time. This could be a reason for tripping the house RCD.

Gerry

[noel shelleyParticipant @noelshelley55608]

Good point Gerry ! Though I think the OPs mention of a light is a static. Noel.

[AlanParticipant @alan14594]

I have a lathe with an inverter…

It occasionally tripped the RCD…

I recently bought a mill with an inverter… It always tripped the RCD…

It worked fine when I powered it from an extension lead from the house (no RCD in the circuit).

Initially, I suspected that it was a switch on current surge, so I constructed a surge limiter….
It made no difference..!!

This breaker was a “Type A” RCD which worked well for its primary purpose of protecting electrical work outside, but can only cope with a pure AC load. Inverters produce harmonics and spikes on the AC input.

I have now replaced this with a “Type B” RCD, which can cope with an inverter style load, and which enables me to power the mill and the lathe with no problem.

Type B RCDs are also required for EV chargers…

Unfortunately, Type B RCDs are more expensive than Type A..!!

Hope this helps!!

 

Alan

[SillyOldDufferModerator @sillyoldduffer]

I fear the worst: ell81 has plugged a shorted motor into his Transwave, and damaged it.   Can only speculate because the Model isn’t identified.    Assuming it’s a Static converter, ell81 may have killed a capacitor or two, and/or an autotransformer, and/or the relay.   Not easy for a beginner to diagnose and fix, and the parts are expensive.

Problem with old motors is it’s difficult to assess condition by eye and plugging them in experimentally is liable to end badly.  Magic smoke, electrocution or a badly dented wallet!   The motor’s history is important:  insulation may have been damaged in the past by overwork, or damp storage, or by passage of time.   And there are many types of motor, with semi-standardised terminal markings, and colour codes: electric motors are confusing.   Understanding what to look for and how to test saves a lot of bother.

ell81 has asked several beginner questions involving old motors and how to wire them.  This is a tricky hobby in itself, so how to start?    What motor books and test equipment would the team recommend to a beginner?   I suggest:

• Books.  Section 12 of Tubal Cain’s Model Engineer’s Handbook is good, though it lacks depth.  My Electrical Engineering books all start with a too simple overview of the basics and then plunge straight into difficult maths, skipping the practical middle bit!  One of them has a couple of hundred pages on single-phase motors with no mention of mere details like centrifugal switches!   “Mere detail” is what I want to know, and finding it requires detective work.   Anyone know of a good practical book on electric motors, or a website.  I’ve not found one!
• Equipment.   At minimum, a neon screwdriver and multimeter, but if recovering old motors is a regular thing, then a high-voltage ohmmeter is essential.   Traditionally a Megger, alternatives available.    An ordinary 1.5V multimeter isn’t enough to test a faulty motor.  A trustworthy insulation test needs 500 or 1000V.   But my view is based on infrequent motor debugging, not best-practice, and is likely to be too simple.   What equipment would an expert recommend?

I bet practitioners have many techniques and tricks of the trade.  Any suggestions?  I plodge through on first-principles which is very slow.

Dave

 

[noel shelleyParticipant @noelshelley55608]

A good multimeter capable of reading high value capacitors and a megger type insulation tester would cover the bulk of what one needs to know to decide if it’s worth trying to save a faulty motor. That may spoil £500 ! Good luck. Noel.

[old martParticipant @oldmart]

When I updated the electrics for the museum’s Tom Senior to a 1hp three phase motor run from an ordinary 13A plug via a Scnieder Altivar inverter which had a built in EMC filter, I was worried about the earth leakage from the filter tripping the workshop 10mA RCD’s. I wanted an EMC filter because a museum is not a domestic situation and did not want the mill to interfere with all the other electrical systems running. So far the earth leakage is not enough to trip any RCD’s. The VFD has a provision to disconnect the EMC filter in the event of it causing trouble.

Alan’s suggestion for changing the RCD may be the best after checking the motor carefully for faults.

 

https://en.wikipedia.org/wiki/Line_filter

[noel shelleyParticipant @noelshelley55608]

Further to my post above on toys, Where an RCD persistently trips an RCD and earth loop tester is very handy. It will give the trip current and also the time taken to do so. Then one knows whether it is excessive imbalance ( leakage ) or an oversensitive RCD. As toys go it is an expensive bit of kit.  Noel.

[alan]

On alan Said:

I have a lathe with an inverter…

It occasionally tripped the RCD…

I recently bought a mill with an inverter… It always tripped the RCD…

It worked fine when I powered it from an extension lead from the house (no RCD in the circuit).

Initially, I suspected that it was a switch on current surge, so I constructed a surge limiter….
It made no difference..!!

This breaker was a “Type A” RCD which worked well for its primary purpose of protecting electrical work outside, but can only cope with a pure AC load. Inverters produce harmonics and spikes on the AC input.

I have now replaced this with a “Type B” RCD, which can cope with an inverter style load, and which enables me to power the mill and the lathe with no problem.

Type B RCDs are also required for EV chargers…

Unfortunately, Type B RCDs are more expensive than Type A..!!

Hope this helps!!

 

Alan

The following video may be of interest here:

This suggests that Type A RCDs would be “blinded” by DC from attached equipment and thus less likely to operate in the circumstances you describe.  Hence the need to use Type B or Type F RCD to provide the required level of additional or fault protection.

Richard

[noel shelley]

On noel shelley Said:

Further to my post above on toys, Where an RCD persistently trips an RCD and earth loop tester is very handy. It will give the trip current and also the time taken to do so. Then one knows whether it is excessive imbalance ( leakage ) or an oversensitive RCD. As toys go it is an expensive bit of kit.  Noel.

Some multifunction testers include a “Ramp” test function which measures the actual residual current which causes the RCD to operate.

Richard

[Bernard WrightParticipant @bernardwright25932]

I had this very problem with a brand new AC/DC Tig welder, I rang the Jasic Aftersales/Technical dept.

I was advised I needed to replace the 40A RCD(this RCD was already in the Consumer Unit) I had wired a 32Amp Isolator into, with at least a 32A MCB.

Never looked back, even use a 32A MCB for my 4kW VFD, with no problems at all.

This is just my experience of 10years, other peoples may vary.

[Robert Atkinson 2Participant @robertatkinson2]

Unfortunatly while replacing a RCD (I hope it was actually a RCBO with over current protection as well as earth leakage) with a MCB is a quick fix for the supplier of the welder it does not properly address the problem (the welder could be faulty). It also reduces the safety in your workshop/home. Not just electric shock risk but fire due to faults to earth.

Robert.

[Bernard Wright]

On Bernard Wright Said:

I had this very problem with a brand new AC/DC Tig welder, I rang the Jasic Aftersales/Technical dept.

I was advised I needed to replace the 40A RCD(this RCD was already in the Consumer Unit) I had wired a 32Amp Isolator into, with at least a 32A MCB.

Never looked back, even use a 32A MCB for my 4kW VFD, with no problems at all.

This is just my experience of 10years, other peoples may vary.

Different problem!     A brand-new welder is unlikely to be faulty, and the after-sales dept would know why it’s likely to upset a Residual Current Breaker and why a circuit breaker is appropriate.

Circuit breakers aren’t a general solution though!   Anyone worried about safety should insist on an RCB because their sensitivity makes electrocution less likely!  RCBs can’t be applied universally though.  Some equipments, like filtered power electronics, legitimately leak enough current to earth to be mistaken for a fault.   Equipments that leak to earth are normally built to minimise the risk, double insulated inside and so forth.

ell81 is playing a different game.  He’s interested in secondhand motors, and some of those he’s asked about here were in poor condition, electrically risky.  Flaky, burnt, or damp insulation.  Loose wires, lethal earth faults and shorts are all possible.  And the motors are removed from the equipment that originally protected their wiring and the operator.  Hence he’s been recommended to test with a multimeter and Megger before connecting to the mains.   In this application, a motor that pops an RCB is almost certainly faulty, and it’s important to make it safe asap.  So a circuit breaker that hides problems is a bad move, especially when a sensitive RCB might save his life if a test goes wrong!

When Bernhard uses his equipment, the electrical lions are safely caged.   Not so when ell81 fault-finds motors; he’s inside the cage busily poking big-cats with a sharp stick!   An RCB might save his life.

Working on live equipment is special.  Many precautions: ideally don’t!  Avoid concrete floors, keep one hand in a pocket, only use the right gear, and assume everything is live, even when absolutely certain it’s dead.   Don’t work alone, and make sure they know what to do when you’re on fire and stuck to an electrode.  Test everything and trust nothing and nobody…  Live work needs a lot of thought, and a risk assessment, and despite that professionals still get killed and burnt.

Dave

[Bernard WrightParticipant @bernardwright25932]

Thing is, a certified Electrician wired this up for me, as the property’s landlord insisted…..

[Robert Atkinson 2Participant @robertatkinson2]

Well most electricians are certifiable 🙂

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